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Structural isomerism in (p-XC6H4)SeCl3 and (p-XC6H4)SeBr3 (X = F, Cl) compounds. Co-crystallisation of cis- and trans-dimeric forms of (p-ClC6H 4)SeCl2(μ-Cl)2(p-ClC6H4)SeCl2. A new structural modification for the "phSeBr" reagent, Ph2Se2Br2, containing an elongated Se-Se bond
A series of di(para-halophenyl)diselenides, (p-XC6H 4)2Se2 (X = F, Cl) have been reacted with three equivalents of SO2Cl2 or Br2, leading to the formation of selenium(iv) RSeX3 compounds. The structures of (p-FC6H4)SeX3 (X = Cl, Br) have been determined, and both exhibit a dimeric RSeX2(μ-X) 2RSeX2 structure consisting of two "saw-horse" (p-FC6H4)SeX3 units linked by two halide bridges, with an overall square pyramidal geometry at selenium. In both structures all the selenium and halogen atoms are planar, with both aryl rings located on the same side of the Se2X6 plane (cis-isomer). The structure of (p-ClC6H4)SeCl3 also adopts a planar dimeric structure, however both cis- and trans-dimeric molecules are co-crystallised in the unit cell. In contrast, the structure of (p-ClC 6H4)SeBr3 adopts a folded cis-dimeric structure due to steric constraints. Secondary Se...X interactions to the "vacant" sixth coordination site at selenium are a feature of most of these structures, but are most prominent in the folded structure of (p-ClC 6H4)SeBr3. A re-examination of the PhSeBr/PhSeBr3 system resulted in the isolation of crystals of a second structural form of "PhSeBr". The structure of Ph 2Se2Br2 consists of two PhSeBr units linked by an elongated Se-Se bond of 2.832(4) A, and longer secondary Se...Br interactions of 3.333(4) A to form a chain structure. Further weak Se...Br and Br...Br interactions are present, which form loosely linked rippled sheets of selenium and bromine atoms, similar to the sheets observed for the tetrameric form, Ph4Se4Br4.
Barnes, Nicholas A.,Godfrey, Stephen M.,Ollerenshaw, Ruth T. A.,Khan, Rana Z.,Pritchard, Robin G.
p. 14583 - 14593
(2012)
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4-Amino-2-(substituted methyl)-2-butenoic acids: Substrates and potent inhibitors of γ-aminobutyric acid aminotransferase
4-Amino-2-(substituted methyl)-2-butenoic acids, where X (the substituted group) = F, Cl, OH, are synthesized from Cbz-protected tert-butyl 4-aminobutanoate. Successive substitutions at the α-carbon by phenylseleno and hydroxymethyl groups, followed by elimination of the selenoxide and halide substitution at the hydroxymethyl group, afford the compounds in good yields. An unexpected degree of stereoselectivity is observed in the selenoxide elimination step, which yields the desired E isomer as the sole product. These compounds complement two previously reported series of compounds (Silverman, R.B.; Levy, M.A. Biochem. Biophys. Res. Commun. 1980, 95, 250-255; J. Biol. Chem. 1981, 256, 11565-11568) and are used in an approach to map a section of the active site of γ-aminobutyric acid aminotransferase (GABA-T). None of these compounds is a time-dependent inactivator of GABA-T, but all are potent competitive reversible inhibitors; the hydroxy compound has a K(i) value of 5 μM. That these compounds are not inactivators suggests that either elimination of X does not occur or that there is no active site nucleophile in the appropriate position for reaction following elimination. With use of the fluoro analogue, enzyme-catalyzed fluoride ion release is demonstrated, indicating that elimination does occur. Unlike the previous two series of compounds (op. cit.) in which exclusive elimination occurs when the substituent is a halogen but exclusive transamination prevails for the hydroxyl-substituted analogues, in the series described here, the fluoro analogue gives a 4:1 ratio of elimination to transamination. This suggests that the 2,3-double bond stabilizes the product of azallylic isomerization of the Schiff base between the fluoro compound and pyridoxal phosphate. The results described here indicate that the design of a mechanism-based inactivator for GABA-T should not be based on electrophile generation near the 2-position of enzyme-bound GABA. Furthermore, substitution of an inhibitor with a 2-hydroxymethyl group (or other hydrogen-bonding substituent) and a 2,3-double bond may lend auspicious binding properties to the molecule for GABA-T.
Silverman,Durkee,Invergo
p. 764 - 770
(1986)
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Diastereoselective Manipulations of Bicyclo[m.1.0]alkane Derivatives. 4. Reactions of Nucleophiles with Bicyclo[m.1.0]alk-3-en-2-ones
Enantiomerically enriched bicyclo[m.1.0]alk-3-en-2-ones possessing 8-, 12-, and 15-membered rings were prepared and subjected to additions of nucleophiles. 1,2-Additions of n-butyllithium were highly diastereoselective for all cyclopropyl enones examined. Reactions of (Z)-bicyclo[6.1.0]non-3-en-2-one and (E)-bicyclo[13.1.0]hexadec-3-en-2-one with dimethyloxosulfonium methylide were highly diastereoselective, while reaction of (E)-bicyclo[10.1.0]tridec-3-en-2-one with this reagent was not diastereoselective. In contrast, 1,4-additions of lithium diorganocuprates were highly diastereoselective for the 8- and 12-membered enones but were not diastereoselective for the 15-membered enone. All reactions were chemically efficient. The diastereoselectivities observed for 1,2-additions, which are thought to involve early transition states, can be rationalized by consideration of the low-energy conformations of each cyclopropyl enone. The diastereoselectivities observed for 1,4-additions, which may involve late transition states, do not correlate simply with the lowest energy conformations of these enones.
Mash, Eugene A.,Gregg, Timothy M.,Baron, James A.
p. 8513 - 8521
(1997)
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Synthesis method of selenium-containing isochroman compound
The invention discloses a synthesis method of a selenium-containing isochroman compound. The synthesis method comprises the following steps: under the protection of nitrogen, adding N-phenylseleno saccharin (NPSSac) into a reactor, then adding dichloromethane to completely dissolve the N-phenylseleno saccharin, adding a 1-[(cinnamoxy) methyl]-3, 4, 5-trimethoxy benzene compound and boron trifluoride diethyl etherate after the N-phenylseleno saccharin is completely dissolved, stirring at 20-60 DEG C for 2-6 hours until the reaction is complete, and after the reaction is finished, quenching, extracting, combining organic phases, drying, concentrating, separating and purifying to obtain the selenium-containing isochroman compound. The synthesis method disclosed by the invention is relatively easy to operate, mild in reaction condition, relatively high in yield, environment-friendly and suitable for large-scale industrial production.
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(2021/05/29)

Synthesis method of 2-benzoxepin compound
The invention discloses a synthesis method of a 2-benzoxepin compound. The method comprises the following specific steps: under the protection of nitrogen, adding N-phenylseleno-phthalimide into a reactor, then adding anhydrous dichloromethane to dissolve the N-phenylseleno-phthalimide, then adding a 1-[(cinnamyl) methyl]-3, 4, 5-trimethoxybenzene compound, taking zinc chloride as a catalyst, reacting at room temperature, adding saturated sodium bicarbonate for quenching after the reaction is finished, extracting by dichloromethane, combining organic phases, drying by anhydrous magnesium sulfate, concentrating under reduced pressure, and performing silica gel rapid chromatographic purification by thin-layer chromatography silica gel to obtain the 2-benzoxepin compound. The method is simple in reaction operation, mild in reaction condition, relatively high in yield, environment-friendly and suitable for large-scale industrialized production.
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(2021/05/29)

A greener protocol for the synthesis of phosphorochalcogenoates: Antioxidant and free radical scavenging activities
In this contribution, a metal- and base-free protocol has been developed for the synthesis of phosphorochalcogenoates (Se and Te) by using DMSO as solvent at 50 °C. A variety of phosphorochalcogenoates were prepared from diorganyl dichalcogenides and H-phosphonates, leading to the formation of a Chal-P(O) bond, in a rapid procedure with good to excellent yields. A full structural elucidation of products was accessed by 1D and 2D NMR, IR, CGMS, and HRMS analyses, and a stability evaluation of the phosphorochalcogenoates was performed for an effective operational description of this simple and feasible method. Typical 77Se{1H} (δSe = 866.0 ppm), 125Te{1H} (δTe = 422.0 ppm) and 31P{1H} (δP = ?1.0, ?13.0 and ?15.0 ppm) NMR chemical shifts were imperative to confirm the byproducts, in which this stability study was also important to select some products for pharmacological screening. The phosphorochalcogenoates were screened in vitro and ex vivo tests for the antioxidant potential and free radical scavenging activity, as well as to investigation toxicity in mice through of the plasma levels of markers of renal and hepatic damage. The pharmacological screening of phosphorochalcogenoates indicated that compounds have antioxidant propriety in different assays and not changes plasma levels of markers of renal and hepatic damage, with excision of 3g compound that increased plasma creatinine levels and decreased plasma urea levels when compared to control group in the blood mice. Thus, these compounds can be promising synthetic antioxidants that provide protection against oxidative diseases.
Mailahn, Daniela H.,Iarocz, Lucas E.B.,Nobre, Patrick C.,Perin, Gelson,Sinott, Airton,Pesarico, Ana Paula,Birmann, Paloma T.,Savegnago, Lucielli,Silva, Márcio S.
(2020/12/07)

Synthesis method of isochroman compound
The invention discloses a synthesis method of an isochroman compound, which comprises the following steps of adding dichloromethane and phosphorus tribromide into 3, 4, 5-trimethoxy benzyl alcohol, and reacting to obtain 1-bromomethyl-3, 4, 5-trimethoxy benzene, adding tetrahydrofuran, cinnamyl alcohol, sodium hydride and 1-bromomethyl-3, 4, 5-trimethoxybenzene into a reactor, and reacting to obtain 1-[(cinnamyl oxy)methyl]-3, 4, 5-trimethoxybenzene, adding cyanuric acid into a reactor containing a potassium hydroxide aqueous solution to react, dropwise adding a silver nitrate aqueous solution, and reacting to obtain silver isocyanurate, adding silver isocyanurate, phenyl selenium bromide and anhydrous dichloromethane into a reactor, and reacting to obtain N, N, N-triphenyl seleno isocyanurate, reacting N, N, N-triphenyl seleno isocyanurate, dichloromethane, boron trifluoride diethyl etherate and a 1-[(cinnamyl oxy)methyl]-3, 4, 5-trimethoxybenzene compound to obtain a target product. The method is simple in reaction operation, mild in reaction condition, relatively high in yield and environment-friendly.
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Paragraph 0046; 0055; 0060; 0069; 0073; 0082

(2021/05/15)

Remarkable alkene-to-alkene and alkene-to-alkyne transfer reactions of selenium dibromide and phsebr. Stereoselective addition of selenium dihalides to cycloalkenes
The original goal of this research was to study stereochemistry of selenium dihalides addition to cycloalkenes and properties of obtained products. Remarkable alkene-to-alkene and alkene-to-alkyne transfer reactions of selenium dibromide and PhSeBr were discovered during this research. The adducts of selenium dibromide with alkenes or cycloalkenes easily exchange SeBr2 with other unsaturated compounds, including acetylenes, at room temperature, in acetonitrile. Similar alkene-to-alkene and alkene-to-alkyne transfer reactions of the PhSeBr adducts with alkenes or cycloalkenes take place. The supposed reaction pathway includes the selenium group transfer from seleniranium species to alkenes or alkynes. It was found that the efficient SeBr2 and PhSeBr transfer reagents are Se(CH2CH2Br)2 and PhSeCH2CH2Br, which liberate ethylene, leading to a shift in equilibrium. The regioselective and stereoselective synthesis of bis(E-2-bromovinyl) selenides and unsymmetrical E-2-bromovinyl selenides was developed based on the SeBr2 and PhSeBr transfer reactions which proceeded with higher selectivity compared to analogous addition reactions of SeBr2 and PhSeBr to alkynes under the same conditions.
Potapov, Vladimir A.,Musalov, Maxim V.,Kurkutov, Evgeny O.,Yakimov, Vladimir A.,Khabibulina, Alfiya G.,Musalova, Maria V.,Amosova, Svetlana V.,Borodina, Tatyana N.,Albanov, Alexander I.
(2020/01/13)

Progress toward a Convergent, Asymmetric Synthesis of Jervine
Progress toward a convergent approach for the enantioselective synthesis of the Veratrum alkaloid jervine is presented. The two requisite fragments were stereoselectively and efficiently fashioned from economical and readily available reagents. Key reactions include (a) a highly diastereoselective Ireland-Claisen rearrangement to establish the necessary cis-relationship between the amine and methyl group on the tetrahydrofuran E-ring; (b) a diastereoselective selenoetherification reaction that enabled the assembly of the D/E oxaspiro[4.5]decene in the needed configuration; and (c) an enzymatic desymmetrization of an abundant achiral diol en route to a key four-carbon building block as a practical alternative to a protected Roche ester reduction.
De Jesús Cruz, Pedro,Johnson, Jeffrey S.,Zavesky, Blane P.
supporting information

(2020/04/30)

Recyclable 1,2-bis[3,5-bis(trifluoromethyl)phenyl]diselane-catalyzed oxidation of cyclohexene with H2O2: A practical access to trans-1,2-cyclohexanediol
1,2-Bis[3,5-bis(trifluoromethyl)phenyl]diselane-catalyzed oxidation of cyclohexene by hydrogen peroxide affords a quick, clean and practical access to the important compound trans-1,2-cyclohexanediol under mild conditions. The highly atom-economic properties, clean procedures, high reaction concentration, short reaction time, mild conditions and eco-friendly, recyclable and low loading catalysts facilitate this methodology for possible future practical industrial production. Copyright
Yu, Lei,Wang, Jun,Chen, Tian,Wang, Yuguang,Xu, Qing
p. 652 - 656
(2014/08/05)

Toward the total synthesis of klaivanolide: Complete reinterpretation of its originally assigned structure
Klaivanolide is an antiparasitic natural product isolated from Uvaria klaineana, whose structure was originally assigned as a seven-membered lactone ring. Attempts towards the total synthesis of klaivanolide led us to revise its original structural assignment based on both experimental evidence and spectroscopic data. The isolated compound was revealed to be a known molecule, acetylmelodorinol, originally isolated from Melodorum fruticosum. Vibrational circular dichroism simulation of the reassigned structure was also performed to reinvestigate our previous studies on the determination of the absolute configuration of klaivanolide.
Ferrié, Laurent,Ferhi, Sabrina,Bernadat, Guillaume,Figadère, Bruno
p. 6183 - 6189
(2015/03/30)

Synthetic approaches to the daucane sesquiterpene derivatives employing the intramolecular Buchner cyclisation of α-diazoketones
The use of the intramolecular Buchner cyclisation of an α-diazoketone as an approach to the synthesis of daucane sesquiterpenes is described; in particular the synthesis of the cis-fused analogue of dihydro CAF-603. The key step in the synthesis is the intramolecular Buchner cyclisation, which provides the bicyclo[5.3.0]decane framework with the required stereochemistry at the quaternary centre generated in the cyclisation. A synthetic route enabling access to an asymmetric synthesis is also outlined.
Foley, David A.,O'Leary, Patrick,Buckley, N. Rachael,Lawrence, Simon E.,Maguire, Anita R.
p. 1778 - 1794
(2013/03/13)

An α-selective, visible light photocatalytic glycosylation of alcohols with selenoglycosides
Exceptionally mild procedures for the visible light photocatalytic activation of selenoglycoside donors in the presence of alcohol acceptors have been developed. This process is demonstrated with both 1-phenylselenyl-2,3,4,6- tetra-O-benzyl glucoside (1) and 1-phenylselenyl-2,3,4,6-tetra-O-benzyl galactoside (2). Catalysis is effected with both metal (Ru(bpy)3) and organocatalysts (diphenyldiselenide). Reactions afford, in all cases, primarily the α-anomers with selectivities that vary with solvent. This represents the first example of a visible light-promoted O-glycosylation.
Spell, Mark,Wang, Xiaoping,Wahba, Amir E.,Conner, Elizabeth,Ragains, Justin
p. 42 - 47
(2013/05/08)

Enantioselective synthesis of oseltamivir phosphate
The key steps in the enantioselective synthesis of Tamiflu include an asymmetric Diels-Alder reaction, Mitsunobu inversion using Fukuyama modified Weinreb reagent, carbamate directed epoxidation. Epoxide opening with trimethylsilyl azide furnished a 3:1 mixture of regioisomers that converged to afford the same aziridine. Attempted preparation of the unsaturated ester regioselectively using 2-iodoxybenzoic acid (IBX) following Nicolaou's protocol failed. The unsaturated ester was prepared by phenylselenylation followed by selenoxide elimination.
Raghavan, Sadagopan,Babu, Vaddela Sudheer
experimental part
p. 2044 - 2050
(2011/04/17)

ZnCl2-catalyzed intramolecular cyclization reaction of 2-aminochalcones using polymer-supported selenium reagent: Synthesis of 2-phenyl-4-quinolones and 2-phenyl-2,3-dihydroquinolin-4(1 H)-one
A new and efficient method for the synthesis of 2-phenyl-4-quinolones and 2-phenyl-2,3-dihydroquinolin-4(1H)-ones is described. The reaction involves ZnCl2-mediated polystyrene-supported selenium-induced intramolecular cyclization of 2-amino-chalcones and subsequent traceless or functionalizing cleavage of selenium linker. Georg Thieme Verlag Stuttgart - New York.
Tang,Chen, Bangzheng,Zhang, Lianpeng,Li, Wen,Lin, Jun
body text
p. 707 - 711
(2011/04/26)

Enantiospecific formal total synthesis of (+)-fawcettimine
The diastereospecific attack of the silyl enol ether on the activated cyclopropyl diester 27 generated the hydrindanone 28 with complete stereocontrol. Thermal decarbomethoxylation of 28 gave the monoester 29, a key intermediate in Heathcocks synthesis, thereby completing a formal total synthesis of (+)-fawcettimine 1. The analogous cyclization of 33, the diastereomer of 27, afforded the diastereomeric diester 34, thereby demonstrating that the cyclization process is diastereospecific.
Jung, Michael E.,Chang, Jonah J.
supporting information; experimental part
p. 2962 - 2965
(2010/09/15)

Heterocyclic photochemistry in contrast with carbon behavior. Regioselective photochemical rearrangement of an azacyclohexadienone: Mechanistic and exploratory organic photochemistry
(Chemical Equation Presented) The Type-A photochemistry of cyclohexadienones is well-studied and follows a well-established mechanistic pathway. One early example is the rearrangement of santonin to lumisantonin. Another example is the rearrangement of 4,4-diphenylcyclohexa-1,5-dienone. Remarkably, replacement of one carbon by nitrogen alters the reaction course to give a regioselective phenyl migration.
Zimmerman, Howard E.,Shorunov, Sergey
experimental part
p. 5411 - 5416
(2009/12/08)

Synthesis, x-ray crystallography, and computational analysis of 1-azafenestranes
The tandem [4+2]/[3+2] cycloaddition of nitroalkenes has been employed in the synthesis of 1-azafenestranes, molecules of theoretical interest because of planarizing distortion of their central carbon atoms. The synthesis of c,c,c,c-[5.5.5.5]-1-azafenestrane was completed in good yield from a substituted nitrocyclopentene, and its borane adduct was analyzed through X-ray crystallography, which showed a moderate distortion from ideal tetrahedral geometry. The syntheses of two members of the [4.5.5.5] family of 1-azafenestranes are also reported, including one with a trans fusion at a bicyclic ring junction which brings about considerable planarization of one of the central angles (16.8° deviation from tetrahedral geometry). While investigating the [4.5.5.5]-1-azafenestranes, a novel dyotropic rearrangement that converts nitroso acetals into tetracyclic aminals was discovered. Through conformational analysis, a means to prevent this molecular reorganization was formulated and realized experimentally with the use of a bulky vinyl ether in the key [4+2] cycloaddition reaction. Finally, DFT calculations on relative strain energy for the 1-azafenestranes, as well as their predicted central angles, are disclosed.
Denmark, Scott E.,Montgomery, Justin I.,Kramps, Laurenz A.
p. 11620 - 11630
(2007/10/03)

Odorless diphenyl diselenide and disulfide: Syntheses and applications
Bis[4-(trimethylsilyl)phenyl]diselenide (3) and bis[4-(trimethylsilyl) phenyl]disulfide (31) are found to be odorless equivalents of the commonly used diphenyl diselenide and diphenyl disulfide, respectively. The diselenide 3 is shown to be useful in the preparation of odorless selenium(II) chloride 26 and selenium(IV) trichloride 28 that follow similar reactivity patterns to their phenyl derivatives and can be stored refrigerated under dry conditions. The corresponding selenium(II) bromide had to be prepared fresh from 3 before use. It is also shown that the trimethylsilyl group in the sulfide products can be protodesilylated quantitatively using TFA. Georg Thieme Verlag Stuttgart.
Patra, Pranab K.,Shanmugasundaram, Kandasamy,Matoba, Manabu,Nishide, Kiyoharu,Kajimoto, Tetsuya,Node, Manabu
p. 447 - 457
(2007/10/03)

Synthesis of cis,cis,cis,cis-[5.5.5.4]-1-azafenestrane with discovery of an unexpected dyotropic rearrangement
(Figure Presented) An unprecedented skeletal reorganization initially hindered a concise route based on a tandem [4+2]/[3+2] nitroalkene cycloaddition for the synthesis of the strained title compound. Conditions to suppress the observed dyotropic rearrangement were developed, and X-ray crystallographic analysis of the BF3 derivative (see picture) of the azafenestrane revealed significant planarization around the central carbon atom.
Denmark, Scott E.,Montgomery, Justin I.
p. 3732 - 3736
(2007/10/03)

Facile One-Step Synthesis of β-Alkoxy Lactone via Sequential Lactonization and 1,4-Addition of Alkoxide Group: Total Synthesis of All Stereoisomers of Dihydrokawain-5-ol
We describe here a divergent total synthesis of all of the four stereoisomers of dihydrokawain-5-ol starting from α-D-glucose. The approach involves the use of Ando's modification of Horner-Wadsworth-Emmons homologation to give a α,β-unsaturated ester. Subsequently, lactonization and 1,4-addition of OMe group in one step provided a γ-lactone, which was converted into the target compounds in two steps.
Singh, Ravi P.,Singh, Vinod K.
p. 3425 - 3430
(2007/10/03)

Selenocyclizations: Control by Coordination and by the Counterion
Selective cyclizations of selenium electrophiles lead to either tetrahydrofurans or lactones (see scheme), depending on the counterions and additives. Modification of the selenium electrophiles allow selective cyclizations, irrespective of the reaction conditions applied.
Khokhar, Shaista S.,Wirth, Thomas
p. 631 - 633
(2007/10/03)

Lewis acid-promoted cyclization of heteroatom-substituted enynes.
Lewis acid-promoted cyclizations of heteroatom-substituted enynes have been examined. The reaction of enynes and bearing silicon substituents on an alkyne afforded the halogenated five-membered gamma-lactones and gamma-lactams as the main products. The reaction of substrates and having 2-phosphonoacrylate instead of malonate also gave halogenated five-membered cyclic compounds and as the major products. The cyclized products are highly substituted and potentially useful for further synthetic transformations.
Yamazaki, Shoko,Yamada, Kuriko,Yamamoto, Kagetoshi
p. 257 - 264
(2007/10/03)

Total synthesis of merrilactone A
This invention provides a total synthesis of Merrillactone and Merrilactone analogues having the structure wherein Z is O or >N—X, where X is H, straight or branched substituted or unsubstituted alkyl, alkenyl or alkynyl, or acyl, carbamoyl, cycloalkyl, aryl, heterocycloalkyl, heteroaryl, aralkyl, amino, alkyl amino, or dialkyl amino; wherein each of R1 and R2 is H or R1 and R2 together are ═O; wherein each of R3 and R4 is H or R3 and R4 together are ═O; wherein each of R5 and R6 is, independently, H, alkyl, aralkyl, or aryl; wherein each of R7 and R8 is, independently, H or OR14, where R14 is alkyl or —C(O)—R15, where R15 is H, —CH2R16, —CHR16R16, —CR16R17R16, —OR16, alkenyl or alkynyl, cycloalkyl, aryl, heterocycloalkyl, heteroaryl, aralkyl, amino, alkyl amino, or dialkyl amino, wherein each R16 is straight or branched, substituted or unsubstituted alkyl, alkenyl or alkynyl, cycloalkyl, aryl, heterocycloalkyl, heteroaryl, aralkyl, or amino; and wherein R17 is straight or branched, unsubstituted alkyl, alkenyl or alkynyl, cycloalkyl, aryl, heterocycloalkyl, heteroaryl, aralkyl, or amino, or wherein R7 and R9 together are >O; wherein each of R9 and R10 is, independently, H, alkyl, OH, or OR13, where R13 is an alkyl, an acyl, or an amide, or R9 and R10 together are ═CH2, or wherein R8 and R10 together are >O; wherein if one of R7 or R8 and one of R9 or R10 is absent, a double bond is formed as indicated by the broken line; and wherein each of R11 and R12 is, independently, H, OH, or OR13, where R13 is an alkyl, an acyl, or an amide, or R11 and R12 together are ═O, or wherein R12 and R10 together are >O, including intermediates in the synthesis.
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Page/Page column 14

(2010/02/05)

Total synthesis of (+)-boronolide, (+)-deacetylboronolide, and (+)-dideacetylboronolide
Total synthesis of (+)-boronolide, (+)-deacetylboronolide, and (+)-dideacetylboronolide has been achieved from a single intermediate 26, which was synthesized in 11 steps from a D-mannitol-derived intermediate 8 in an overall yield of 10%. The key steps in the synthesis are inversion of a chiral center by taking an advantage of the inherent mechanism involved in the ring closing to an epoxide via intramolecular SN2 reaction and lactonization of a diol using Fetizons reagent. The strategy is amenable to preparation of analogues of (+)-boronolide in sufficient amount for further screening of biological activity.
Chandrasekhar,Chandra, Kusum L.,Singh, Vinod K.
p. 4039 - 4045
(2007/10/03)

PhSeOTf-Et3N·3HF and PhSeSbF6-Et3N·3HF as new PhSe-F equivalents in the fluoroselenenylation of actylenes
The novel reagents PhSeOTf-Et3N·3HF and PhSeSbF6-Et3N·3HF act as PhSe-F equivalents in the fluoroselenenylation of alkynes. Oct-4-yne, cycloundecyne and cyclododecyne, as well as the unsymmetrical alkynes Ph-C≡C-Me and Bu-C≡C-R (R = Me, Et, iPr and tBu) give the corresponding (E)-fluoro(phenylseleno)alkenes in preparative yields. The reagent PhSeOTf-Et3N·3HF gives a similar product composition of regioisomers to Ph2Se2-XeF2 in addition reactions to Bu-C≡C-R. This is indicative of a similar reaction mechanism of the reagents. Probably a selenirenium ion acts as an intermediate. X-Ray single crystal structure analysis of (E)-1-fluoro-2-phenylselenocycloundecene confirms the trans-addition of [PhSe-F] to cycloundecyne.
Poleschner, Helmut,Seppelt, Konrad
p. 2668 - 2672
(2007/10/03)

Quantitative cavities and reactivity in stages of crystal lattices: Mechanistic and exploratory organic photochemistry
In continuing our research on solid-state organic photochemistry, we have been investigating the phenomenon of reactivity in stages. In this study we present new examples where the photochemical reactivity changes discontinuously at some point in the conversion. In these instances, the reaction course of the solid differs from that in solution. One example is the reaction of 2-methyl-4,4-diphenylcyclohexenone, where an unusual reaction course was encountered in the solid state; and, of two possible mechanisms, one was established by isotopic labeling. A second case is that of 4,5,5-triphenylcyclohexenone. The solid-state reaction of this enone was found to give a new photochemical transformation, the Type C rearrangement, a process that involves a δ to α aryl migration. In the case of 3-tert-butyl-5,5-diphenylcyclohexenone the Type C rearrangement occurred even in solution. The stage behavior was investigated using X-ray analysis and Quantum Mechanics/Molecular Mechanics computations. This permitted us to determine the sources and details of the stage phenomenon. The analysis revealed how a product molecule as a neighbor affects reactivity. The computations were employed to follow the course of a solid-state reaction from reactant through the succeeding stages. Additionally, the Delta-Density Analysis was utilized to ascertain the electronic nature of molecular changes. Besides product composition changing with extent of conversion, the reaction quantum yield was found to change as one stage gave way to a succeeding one.
Zimmerman, Howard E.,Nesterov, Evgueni E.
p. 2818 - 2830
(2007/10/03)

Mixed acetals as new precursors for selenium electrophiles
A wide range of precursors for selenium electrophiles is already known, but the requirements for the development of polymer-bound selenium reagents are different. Herein we report mixed acetals as new precursor molecules for the synthesis of selenium electophiles under very mild reaction conditions. The use of (MeOCH2Se)2 allows a very fast access to these mixed acetals. Chiral precursor molecules can be synthesized as well and employed in efficient stereoselective selenenylation reactions.
Uehlin, Lars,Wirth, Thomas
p. 189 - 194
(2007/10/03)

A generalized exo-anomeric effect. Substituent and solvent effects on the conformational equilibria of 2-(Arylseleno)cyclohexanones
The effects of substitution and solvent on the conformational equilibria of 2-[(4-R-substituted-phenyl)seleno]cyclohexanones are described. The conformational equilibria were determined by comparison of the linewidths of the H-2 resonances in the 1H NMR spectra of the conformationally averaged systems with those of the anancomeric (highly biased) 4-isopropyl-2-substituted cyclohexanones. The substituent (R = NMe2, OMe, Me, H, F, Cl, CF3, NO2) and solvent ((CD3)2CO, CD3CN, CD2Cl2, CDCl3) effects are discussed in terms of electrostatic effects and the possible stabilizing orbital interactions. The values of Keq (axial-equatorial) increase as the substituent becomes more electron withdrawing, in agreement with the dominance of nSe→π*C=O or σC-Se→π*C=O orbital interactions in the axial conformers. The increase in the proportion of the equatorial isomers in more polar solvents for a given substituent suggests a damping of the dipolar interactions in the equatorial isomers. However, the proportion of the equatorial isomers in a given solvent increases as the substituent becomes more electron withdrawing, indicating that electrostatic interactions do not dominate in controlling the conformational equilibria. Analysis of the equilibrium data by means of a dual substituent parameter approach indicates the best correlation with σI and σ+R substituent constants in CD2Cl2, and with σI and σOR substituent constants in CD3CN, with similar sensitivities to the resonance and polar effects. The correlations are interpreted in terms of accommodation of effective positive charge on the selenium atom in the axial isomers in CD2Cl2, and a lesser sensitivity to the buildup of positive charge in the more polar solvent CD3CN. Comparison of the IR vCO-stretching frequencies for the axial and equatorial ArSe-substituted anancomeric systems (R = NO2, NMe2) indicates a higher stretching frequency for the NO2-substituted isomers. In the case of the NMe2-substituted compounds, vCO appears at a higher frequency in the equatorial isomer, whereas in the case of the NO2-substituted compounds, vCO is less sensitive to the axial or equatorial orientation of the substituent. The results are consistent with the operation of nSe→π*C=O or σC-Se→π*C=O orbital interactions in the axial isomers. The JC2-H2 values in the axially-substituted anancomeric isomers are of greater magnitude than those in the equatorially-substituted isomers, which is also consistent with the operation of the orbital interactions described above. There is, however, no marked substituent effect on the JC2-H2 values within the series of axial or equatorial isomers. We argue that this does not support the dominance of σC-Se→π*C=O orbital interactions. Examination of crystal structures reported in the literature for related compounds indicates a particular gauche orientation about the C2-Se bond, which lends further support to the operation of an nSe→π*C=O orbital interaction. We suggest that the latter interaction is a manifestation of a generalized exo-anomeric effect.
McLeod, Ronald G.,Johnston, Blair D.,Pinto, B. Mario
p. 307 - 316
(2007/10/03)

Intermolecular and intramolecular reactions of resolved 2-alkoxytetrahydrofuran-3-yl and 2-alkoxytetrahydropyran-3-yl radicals
Diastereomeric trans-2-alkoxy-3-phenylselenenyltetrahydrofuranyl acetals and trans-2-alkoxy-3-phenyl-selenenyltetrahydropyranyl acetals were prepared from dihydrofuran, dihydropyran, phenylselenenyl bromide, and the alcohols (S)-methyl lactate, (S)-methyl hexahydromandelate, and (R)-pantolactone. The diastereomers were chromatographically separated and were subjected to intermolecular alkylation via generation and trapping of free radicals. Observed diastereoselectivity was higher for 2-alkoxytetrahydrofuran-3-yl radicals than for 2-alkoxytetrahydropyran-3-yl radicals, and highest for acetals involving (R)-pantolactone. Alcohol exchanges at the anomeric carbon were highly stereocontrolled, and permitted introduction of alkenes for intramolecular trapping of free radical intermediates. (C) 2000 Elsevier Science Ltd.
Nimkar, Kalpana S,Mash, Eugene A
p. 5793 - 5800
(2007/10/03)

[2 + 1] Cycloaddition Reactions of a 1-Seleno-2-silylethene to 2-Sulfonylacrylates: Stereoselective Synthesis of Sulfone-Substituted Cyclopropanes
Reaction of 1-(phenylseleno)-2-(trimethylsilyl)ethene 1 and methyl or ethyl 2-p-toluene- or benzene-sulfonylacrylates 3 in the presence of SnCl4 at -78°C gave sulfone-substituted cyclopropanes 4 as single stereoisomers. The structure of one of these crystalline cyclopropane products was elucidated by X-ray crystallographic analysis. The relative stereochemistry of the cyclopropane ring carbon (C2) and selenosilylmethyl group was determined as R,R and S,S, which is consistent with previous mechanical considerations and the NOE determination. 2-Sulfinyl acrylate 2 did not undergo this cycloaddition. The difference in reactivity of the sulfoxide 2 and sulfones 3 toward 1 was explained by comparison of LUMO levels of 2-SnCl4 and 3-SnCl4 complexes and activation energies in the synclinal addition of 1 to the complexes.
Yamazaki, Shoko,Yanase, Yuichiro,Tanigawa, Etsuko,Yamabe, Shinichi,Tamura, Hatsue
p. 9521 - 9528
(2007/10/03)

Synthesis of (±)-calicheamicinone by two methods
Ketene acetal 25 was converted into silyl enol ether 20, which underwent a Diels-Alder reaction with methyl (E)-3-nitropropenoate to afford ketone 27. This was converted by two routes into (±)calicheamicinone (1). In the first, modification of the nitro, ester, and allyl substituents gave ketone 38, which reacted stereoselectively with cerium trimethylsilylacetylide to place the acetylene unit syn to the nitrogen function (38 → 39). Further elaboration took the route as far as aldehyde 42. A slightly different series of reactions served to convert ketone 27 into tricyclic ketone 43. This also reacted with cerium trimethylsilylacetylide, but in the opposite stereochemical sense to 38, so as to place the acetylene unit anti to the nitrogen function (43 → 50). Further elaboration took this second route as far as lactone 44. Both 42 and 44 serve as advanced intermediates for the synthesis of (±)-calicheamicinone. The monoacetylenic aldehyde 42 reacted stereoselectively with cerium trimethylsilylacetylide to give the bis(acetylene) 53 as the major product. This was elaborated into lactone 60, which was desaturated (60 → 68) and methoxycarbonylated on nitrogen. The acetylenic silyl groups were then removed, so as to generate syn bis(acetylene) 72, and the terminal acetylenic hydrogens were replaced by iodine. The resulting diiodide 81 formed the cyclic enediyne 82 on reaction with (Z)-1,2-bis(trimethylstannyl)ethene in the presence of (Ph3P)4Pd, and the enediyne was converted into (±)calicheamicinone. syn-Bis(acetylene) 72 was also synthesized from the other advanced intermediate (lactone 44), using, as a key step, free radical bromination of the derived unsaturated lactone 77. The resulting bromo lactones 78 were converted into an aldehyde ester 79, and this reacted stereoselectively with cerium trimethylsilylacetylide to give 80, convertible by the action of TBAF into 72.
Clive, Derrick L.J.,Bo, Yunxin,Tao, Yong,Daigneault, Sylvain,Wu, Yong-Jin,Meignan, Gérard
p. 10332 - 10349
(2007/10/03)

Lewis Acid-Promoted [2 + 1] Cycloaddition Reactions of a 1-Seleno-2-silylethene to 2-Phosphonoacrylates: Stereoselective Synthesis of a Novel Functionalized α-Aminocyclopropanephosphonic Acid
Stereoselective SnCl4-promoted [2 + 1] cycloaddition reactions of 1-seleno-2-silylethene 1 with 2-phosphonoacrylates 2 lead to highly functionalized cyclopropanephosphonate esters 3 in high yields. The cyclopropane products 3 are potentially versatile starting materials for biologically important compounds. Stereoselective synthesis of a novel functionalized α-aminophosphonic acid derivative, an analogue of (Z)-2,3-methanohomoserine 13, from the cycloadduct 3b was achieved. Stereoselectivity in the [2 + 1] cycloaddition was explained by consideration of the structure of the 2-SnCl4 complex.
Yamazaki, Shoko,Takada, Takashi,Imanishi, Tomomi,Moriguchi, Yumiko,Yamabe, Shinichi
p. 5919 - 5928
(2007/10/03)

Photochemistry in a crystalline cage. Control of the Type-B bicyclic reaction course: Mechanistic and exploratory organic photochemistry
Our current theories on crystal lattice control of organic photochemistry were subjected to studies of type-B rearrangement of bicyclo[3.1.0]hex-3-en-2-ones. A first finding was that the solid state photochemistry differed dramatically from that in solution. One of our past observations in this bicyclic photochemistry in solution was that the six-membered ring, type B, zwitterion was a ubiquitous intermediate. This intermediate invariably underwent a preferential migration of an aryl group to carbon-2 relative to carbon-4 with formation of a 2,3-disubstituted phenol, a result deriving from electronic effects. In contrast, the crystal lattice photochemistry revealed a regioselectivity depending on the surrounding lattice rather than electronics. Perhaps an even more dramatic difference was an observation of the dependence of reactant stereochemistry. Thus, in solution, for 6,6-disubstituted bicyclics with two different groups at C-6, a common zwitterion is formed and the same photoproduct is formed independent of reactant stereochemistry. In crystal lattices the endo and exo stereoisomers of the 6,6-disubstituted bicyclics react differently and the group originally endo tends to migrate after three-ring opening to the zwitterion. The experimental results were paralleled with a theoretical analysis. This consisted of generation of a 'mini crystal lattice' with sufficient lattice molecules to completely surround a central, reacting electronically excited state molecule. Then computational extraction of the central molecule and replacement by a transition structure afford a model of the reacting excited state inside the crystal lattice. Overlap of this species with the lattice neighbors and energy computations are then possible. These permit prediction and understanding of excited state crystal lattice reactivity on a quantitative basis.
Zimmerman,Sebek
p. 3677 - 3690
(2007/10/03)

The synthesis and some manipulations of dialkyl 6-aryl(or alkyl)-2-oxotetrahydro-2H-pyran-3,5-dicarboxylates
A new, one-pot annulation process, involving conjugate addition of the sodium salts of dimethyl (or dibenzyl) malonate to alkyl 2-(l-hydroxyalkyl)propenoates, produces a mixture of dialkyl 6-aryl(or alkyl)-2-oxotetrahydro-2H-pyran-3,5-dicarboxylates. Alkylations of the cis-isomers were found to be highly stereoselective. The introduction of unsaturation into these molecules is also described.
Lawrence, Ron M.,Perlmutter, Patrick
p. 839 - 845
(2007/10/03)

Asymmetric Lewis Acid-Catalyzed Addition of a Ketene Dithioacetal to a Chiral Bicyclic Lactam. Formation of Cyclobutanopyrrolidinones. A New Class of GABA Derivatives
Additions to unsaturated chiral lactams 8 using methylenedithiolane, gave very high endo-selectivity of the cyclobutane adducts (2 + 2 addition) 13, 16.Removal of the phenylglicinol auxiliary by reductive cleavage products the title compound (+)-20 in very high (>99percent) enantiomeric excess.Absolute stereochemistry of the cyclobutanopyrrolidinone, containing three contiguous stereocenters, was confirmed by X-ray crystallography.
Meyers, A. I.,Tschantz, Matt A.,Brengel, Gregory P.
p. 4359 - 4362
(2007/10/02)

Studies on the Free Radical Carbon-Carbon Bond Formation in the Reaction of α-Phosphoryl Sulfides and Selenides with Alkenes
α-Mono- and α,α-disubstituted α-phosphoryl radicals 9 were generated from the easy accessible α-phosphoryl sulfides 4, 5 and α-phosphoryl selenides 11, 12 and reacted with the electron rich alkenes 6 under the reductive (n-Bu3SnH/AIBN) conditions to give the functionalized phosphonates 7 in 32+68percent yield.Two fragmentation processes of the phosphonate α-alkoxy alkyl radicals are also described. - Key words: α-phosphoryl sulfides, α-phosphoryl selenides, intermolecular radical reaction, radical fragmentation, phosphonates, tri-n-butyltin hydride, α,α'-azaisobutyronitrile
Balczewski, Piotr,Pietrzykowski, Witold M.,Mikolajczyk, Marian
p. 7727 - 7740
(2007/10/02)

Theoretical and Experimental Studies of Regioselectivity in Selenoxide Elimination
In order to gain insight into the mechanism of selenoxide elimination, the transition state structures have been determined by applying the ab initio MO method to the elimination for systems having a simplified skeleton, CH2(Y)CH(Se(O)CH3)CH3 (Y = OCH3, OH, CN and Cl).The calculations show that an allylic alkyl ether and an allylic alcohol ahould be produced preferentially in the case of Y = OCH3 and OH, respectively, whereas a vinylic cyanide should be the major product in the case of Y = CN.The chloro-substituted model has given a result most consistent with the methoxy-substituted model.The elimination occurs via a transition state with a five-membered ring structure, and the breaking of the Cβ-H bond takes place earlier than that of the Se-Cα bond, in the favorable path.The asynchronous nature of bond breaking is quite conspicuous in the cyano-substituted model, relative to the other systems.For comparison with the theoretical results, β-methoxy-, β-hydroxy-, β-cyano-, and β-chloro-substituted selenides were newly synthesized from trans-7-tetradecene, respectively, and were oxidized by H2O2 in tetrahydrofuran or in carbon tetrachloride.The regioselectivity observed for the elimination, i.e., the formation of a vinylic compound from the β-cyano selenide and a mixture of allylic and vinylic products from the β-chloroselenide, agrees well with the theoretical calculations.The difference in the activation energies of the two paths calculated for the model species is not large enough in the methoxy- and hydroxy-substituted selenides to explain the almost complete formation of an allylic compound in the physical experiments.
Kondo, Noboru,Fueno, Hiroyuki,Fujimoto, Hiroshi,Makino, Mineyuki,Nakaoka, Hiroaki,et al.
p. 5254 - 5263
(2007/10/02)

A Novel Competition between C-Se and C-Si Cleavage in Cyclization of β-Seleno-β-silyl-substituted Divinyl Ketones
Reactions of β-seleno-β-silyl-substituted divinyl ketones 2-4 with Lewis acid at room temp. gave phenylseleno and/or trimethylsilyl functionalized cyclopentanones.The use of TiCl4 or SnCl4 results in C-Se cleavage leading to 5-(phenylseleno)-3-(trimethylsilyl)cyclopent-2-enones 9-11 as major products.In contrast, using AgBF4-TMSCl (trimethylsilyl chloride) results in C-Si cleavage to give 3-(phenylseleno)cyclopenten-2-ones 12-14.Lewis acid-dependent competitive cleavage between C-Se and C-Si bonds has been demonstrated.
Yamazaki, Shoko,Mizuno, Wataru,Yamabe, Shinichi
p. 1555 - 1560
(2007/10/02)

PREPARATION OF PHENYL TRIHALOVINYL SELENIDES AND SELENOXIDES
Phenyl trichlorovinyl selenide and phenyl 1,2-dichloro-2-bromovinyl selenide were obtained by the addition of phenylselenenyl chloride and bromide to dichloroacetylene with catalysis by Lewis acids.Hydrogen peroxide oxidation gave the corresponding selenoxides.
Martynov, A. V.,Mirskova, A. N.
p. 2106 - 2108
(2007/10/02)

Synthese und Koordinationsverhalten von Selenoalkinylen R-Se-CC-R'
Synthesis and Coordination Ability of Selenoalkynes R-Se-CC-R' Several synthetic methods for the preparation of selenoalkynes R-Se-CC-R'(1) are discussed. 1 reacts with octacarbonyl dicobalt to yield the η2-?-side-on coordinated alkyne complexes R-Se2-CC-R')Co2(CO)6> (8) which contain a sterically hindered carbon-cobalt tetrahedrane cluster unit.The identity of compounds 1 and 8 is documented by analytical and spectroscopic (IR, MS, 1H-, 77Se-, and 13C-NMR) data as well as by X-ray analysis of C6H5-Se2-CC-C6H5)Co2(CO)6> (8a).
Lang, Heinrich,Keller, Holger,Imhof, Wolfgang,Martin, Sabine
p. 417 - 422
(2007/10/02)

Azapsoralens. Synthesis of 8-Azapsoralens
The synthesis of some N-methyl-8-azapsoralen salts 1 is described for use as water-soluble analogues of psoralens.A key intermediate is the furopyridine carboxaldehyde 16 prepared in four steps from simple acyclic precursors.The pyrone ring is fused on by first extending the carbon chain via a Reformatsky or Doebner condensation followed by deprotection and ring closure.Since stability of this ring system in water is crucial to its potential use as a nucleic acid cross-linking reagent, rates of pyrone hydrolysis for the N-methylazapsoralens were measured.Sufficient stability in the necessary pH range was found for several analogues.
VanSickle, Andrew P.,Rapoport, Henry
p. 895 - 901
(2007/10/02)

Photochemistry of Some Extended ?-Systems: Type A and Aryl Rearrangements of Systems with Extended Conjugation Related to Cyclohexadienones and Cyclohexenones. Mechanistic and Exploratory Organic Photochemystry
6,6-Diphenyl-2(6H)-naphthalenone and 5,6,6-triphenyl-2(6H)-naphthalenone were sinthesized as extended relatives of 4,4-diphenylcyclohexadienone and their photochemistry was investigated.In the case of the diphenylnaphthalenone, irradition resulted in a regioselective phenyl migration and formation of 5,6-diphenyl-2-naphthol whether the photolysis was in methanol or in benzene.Irradiation of the triphenylnaphthalenone in methanol or isopropyl alcohol afforded a product in which one molecule of solvent and one molecule of molecular oxygen were incorporated.Photolysis in acetonitrile led instead to a tricyclic photoproduct in a process reminiscent of the type A rearrangement of 2,5-cyclohexadienones.This tricyclic photoproduct itself was photochemically reactive and rearranged regioselectively to afford 5,7,8-triphenyl-2-naphthol.By trapping, a tricyclic zwitterion was shown to play a role in the rearrangement of the triphenylnaphthalenone.The photochemystry of both naphthalenones was shown by quenching to result from triplet excited states.Lack of reactivity on sensitization suggested the photochemystry derives from Tn.The quantum efficiencies were shown to be lower and the triplet reaction rate slower in the comparison with the monocyclic 4,4-diphenylcyclohexadienone.Finally, enone analogues were investigated.Both 6,6-diphenyl-4,4a,5,6-tetrahydro-2(3H)-naphthalenone and 6,6-diphenyl-4,4a,5,6,10,10a-hexahydro-2(3H)-anthracenone were synthesized.Only the former was reactive; phenyl migration resulted in formation of four stereoisomeric tricyclic ketones whose structures were established by X-ray analysis.For all of the various reactions, mechanisms are provided and discusseed along with MNDO-CI computations.
Zimmerman, Howard E.,Lamers, Paul H.
p. 5788 - 5804
(2007/10/02)

ADDITION OF AMINOKETENE DITHIOACETALS TO α,β-UNSATURATED KETONES. SYNTHESIS AND REACTIONS OF CYCLOHEX-2-EN-1,4-DIONE MONODITHIOACETALS
Aminoketene dithioacetals add to α,β-unsaturated ketones to give 1,5-diketones after hydrolytic work-up.Upon treatment with acid or base, these diketones suffer intramolecular aldol reactions yielding cyclohex-2-en-1,4-dione monodithioacetals, interesting and useful synthetic equivalents of cyclohex-2-en-1,4-diones which readily undego conjugate addition and cycloaddition reactions.
Page, Philip C. Bulman,Harkin, Shaun A,Marchington, Allan P.,Niel, Monique B. van
p. 3819 - 3838
(2007/10/02)

New practical synthesis from (S)-(+)-glutamic acid of the (+)-12-[2]-tetrahydropyranoxyether of 12-(R)-hydroxy-8-E-10-E-14-Z-n.tetradecatriene-7-triphenylphosphonium bromide, synthesized with 14 C using LTB4
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Pirillo,Di Giacomo,Portaluppi,Azzolina,Vercesi,Borgna,Traverso
p. 839 - 849
(2007/10/02)

SYNTHESIS OF BOTH THE ENANTIOMERS OF DIHYDROACTINIDIOLIDE, A PHEROMONE COMPONENT OF THE RED IMPORTED FIRE ANT
Both the enantiomers of dihydroactinidiolide (4,4,7a-trimethyl-2-oxo-2,4,5,6,7,7a-hexahydrobenzofuran) were synthesized in 15 steps from (S)-3-hydroxy-2,2-dimethylcyclohexanone
Mori, Kenji,Nakazono, Yutaka
p. 283 - 290
(2007/10/02)

Intramolecular Amidoselenation of N-Alkenyl Imidates to N-Heterocycles
The reactions of N-alkenyl imidates with benzeneselenenyl chloride and bromide in chloroform at ambient temperature afford pyrrolidine and piperidine derivatives having a phenylseleno moiety in good to excellent yields under neutral conditions.The key step of this new reaction consists of an intramolecular carbon-nitrogen bond formation and a simultaneous carbon-oxygen bond fission.
Terao, Keiji,Toshimitsu, Akio,Uemura, Sakae
p. 1837 - 1844
(2007/10/02)

The addition of electophiles on ester enolates containing an oxygen in the β-position. A stereoelctronically controlled reaction
The enolate anion derived from spiro ketal methyl esters (1,3, and 4) reacts with various electrophiles (PhSeBr, CH3I, O2, I2, (CH3S)2, and (PhS)2 to yield as the major product, the isomer resulting from an equatorial approach of the electrophilic reagent.This stereochemically controlled reaction is discusseed in terms of stereoelectronic effects that increase the electron density of the α face of the enolate anion.
Caron, Maurice,Kawamata, Takeshi,Ruest, Luc,Soucy, Pierre,Deslongchamps, Pierre
p. 1781 - 1787
(2007/10/02)

Reactions of α-Diazo Ketones with Selenium-based Reagents. A General Synthesis of α-Chloro-, α-Bromo, α-Phenylseleno-, α-Acetoxy-, and α-Methoxy-αβ-unsaturated Ketones
Benzeneselenenyl derivatives, PhSe-X (X=Cl, Br, OCOCH3, and SCN) react readily with α-diazo ketones, RCOC(N2)R1 (R1=H or alkyl), with loss of nitrogen, furnishing αα-adducts of the type RCOCR1(X)SePh.The α-chloro and α-bromo adducts can be converted into α-methoxy adducts in methanol-sodium hydrogen carbonate.The utility of these adducts in synthesis is illustrated by their conversion (where structural considerations permit) via selenoxide fragmentation into α-heterosubstituted αβ-unsaturated ketones.Treatment of the series RCOCR1(X)SePh (R1=alkyl; X=Cl, Br, OCOCH3, and OCH3) with hydrogen peroxide-pyridine produces α-chloro-, α-bromo-, α-acetoxy-, and α-methoxy-αβ-unsaturated ketones, whereas treatment of series RCOCR1(X)SePh (R1=alkyl; X=Cl and Br) with lithium carbonate in dimethylformamide produces α-phenylseleno-αβ-unsaturated ketones.Several α-substituted cyclopentenones, cyclohexenones, and cycloheptenones have been synthesised in this way and acyclic examples are illustrated by the synthesis of 3-chloro-, 3-bromo-, 3-acetoxy-, 3-methoxy,-and 3-phenylselenobut-3-en-2-one from 3-diazobutan-2-one.
Buckley, Daniel J.,McKervey, M. Anthony
p. 2193 - 2200
(2007/10/02)

A Convenient Synthesis of Se-Aryl Oxoarylmethanesulfenoselenoates and Te-Aryl Oxoarylmethanesulfenotelluroates: Electrophilic Thiocarboxylation of Diaryl Diselenides and Ditellurides
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Kato, Shinzi,Kabuto, Hiroyuki,Kimura, Masahiro,Ishihara, Hideharu,Murai, Toshiaki
p. 519 - 520
(2007/10/02)