cas 29576-14-5, CROTYL BROMIDE TECH. 85 | Articles data

Articles about 29576-14-5Total 42 be found

Article title
Article abstract
Author
Journal number and time
Download

An acyl-Claisen/Paal-Knorr approach to fully substituted pyrroles
The synthesis of fully substituted pyrroles using the Paal-Knorr reaction on acyl-Claisen derived 2,3-syn-disubstituted-1,4-diketones is reported. The use of the acyl-Claisen rearrangement allows the synthesis of wide variety of syn-substituted 1,4-diketones which are shown to be better substrates for pyrrole condensation than their corresponding anti isomers. When the reaction was performed open to air the use of nucleophilic amines in the pyrrole forming step leads to auto-oxidation of the 5-methyl group giving exclusively 5-formyl pyrroles.
Dittrich, Nora,Jung, Eun-Kyung,Davidson, Samuel J.,Barker, David
p. 4676 - 4689
(2016)
Read Online

Local Conformer Effects in Unsaturated Lactones
Allylic unsaturated lactones 5E and 5Z can be epoxidized and osmylated with useful stereocontrol.The epoxidations follow the pattern predicted from evaluation of local conformer effects, and epoxides 8 and 14 are favored.These products correspond to peripheral attack on the exposed olefin face of conformers similar to 1 (Z-alkene) or 2 (E-alkene).As in the case of simple carbocyclic alkenes, osmylation of the Z-isomer (5Z) follows the same selectivity pattern as the epoxidation, and 16 is the major diol.However, the isomeric 5E is osmylated from the opposite olefin face compared to the epoxidation and gives 13 as the major diol.The analysis of epoxidations by the local conformer approach is compared with the results of molecular mechanics (MACROMODEL) evaluations of the favored conformers of 5E and 5Z and of the derived epoxides.
Vedejs, E.,Dent, W. H.,Gapinski, D. M.,McClure C. K.
p. 5437 - 5446
(1987)
Read Online

-
-
Fieser
(1928)
Read Online

A mild method for the replacement of a hydroxyl group by halogen: 3. the dichotomous behavior of α-haloenamines towards allylic and propargylic alcohols
A study of the deoxyhalogenation of allylic and propargylic alcohols with tetramethyl-α-halo-enamines is reported. Primary allylic and primary and secondary propargylic alcohols gave the corresponding halides in high yields. Secondary allylic and propargylic alcohols yielded the corresponding secondary halides but the reaction also produced some rearranged primary halides (I > Br > Cl). The reactions with tertiary allylic and tertiary propargylic alcohols gave several products and was therefore of little synthetic value. However, the addition of triethylamine to the reaction mixture or the use of lithium alkoxide instead of alcohol brought about a major change of the course of the reaction which led to amides carrying an allyl or an allenyl group at C2. This was shown to result from a Claisen-Eschenmoser rearrangement of an intermediate α-allyloxy- or propargyloxy-enamine.
Munyemana, Fran?ois,Patiny, Luc,Ghosez, Léon
(2021/06/07)

Alkyne Aminopalladation/Heck and Suzuki Cascades: An Approach to Tetrasubstituted Enamines
Alkyne aminopalladation reactions starting from tosylamides are reported. The emerging vinylic Pd species are converted either in an intramolecular Heck reaction with olefinic units or in an intermolecular Suzuki reaction by using boronic acids exhibiting broad functional group tolerance. Tetra(hetero)substituted tosylated enamines are obtained in a simple one-pot process.
Geffers, Finn J.,Jones, Peter G.,Kurth, Florens R.,Werz, Daniel B.
supporting information
p. 14846 - 14850
(2021/10/19)

Regiospecific Synthesis of Calcium-Independent Daptomycin Antibiotics using a Chemoenzymatic Method
Daptomycin (DAP) is a calcium (Ca2+)-dependent FDA-approved antibiotic drug for the treatment of Gram-positive infections. It possesses a complex pharmacophore hampering derivatization and/or synthesis of analogues. To mimic the Ca2+-binding effect, we used a chemoenzymatic approach to modify the tryptophan (Trp) residue of DAP and synthesize kinetically characterized and structurally elucidated regiospecific Trp-modified DAP analogues. We demonstrated that the modified DAPs are several times more active than the parent molecule against antibiotic-susceptible and antibiotic-resistant Gram-positive bacteria. Strikingly, and in contrast to the parent molecule, the DAP derivatives do not rely on calcium or any additional elements for activity.
Mupparapu, Nagaraju,Lin, Yu-Hsin Cindy,Kim, Tae Ho,Elshahawi, Sherif I.
supporting information
p. 4176 - 4182
(2021/02/01)

Visible-Light-Promoted Intramolecular α-Allylation of Aldehydes in the Absence of Sacrificial Hydrogen Acceptors
We report herein an unprecedented protocol for radical cyclization of aldehydes with pendant alkenes via synergistic photoredox, cobaloxime, and amine catalysis. The transformation was achieved in the absence of external oxidants, providing a variety of 5-, 6-, and 7-membered ring products with alkene transposition in satisfactory yields. The reaction exhibits wide functional group compatibility and occurs under mild conditions with extrusion of H2.
Liu, Feng,Liu, Jia-Li,tu, Jia-Lin
supporting information
p. 7369 - 7372
(2020/10/05)

Ruthenium-catalyzed enantioselective C-H functionalization: A practical access to optically active indoline derivatives
Ru(II)-catalyzed enantioselective C-H activation/hydroarylation has been developed for the first time, allowing for highly enantioselective synthesis of indoline derivatives via catalytic C-H activation. Commercially available Ru(II) arene complexes and chiral α-methylamines were employed as highly enantioselective catalysts. Based on a sterically rigidified chiral transient directing group, multisubstituted indolines were produced in up to 92% yield with 96% ee. Further transformation of the resulting 4-formylindoline enables access to an optically active tricyclic compound that is of potential biological and pharmaceutical interest.
Li, Zhong-Yuan,Lakmal, Hetti Handi Chaminda,Qian, Xiaolin,Zhu, Zhenyu,Donnadieu, Bruno,McClain, Sarah J.,Xu, Xue,Cui, Xin
supporting information
p. 15730 - 15736
(2019/10/11)

ATF3 INDUCTION COMPOUNDS
Provided are compounds for treating and/or preventing obesity and obesity-related disorders. Particularly, provided are chromanone derivatives used as ATF3 inducer and for treating and/or preventing obesity and obesity-related disorders such as heart disease, hypertension, hyperlipidemia and diabetes.
-
Paragraph 0083; 0085

(2018/10/19)

Forging C-C Bonds with Hindered Nucleophiles and Carbonyl Electrophiles: Reactivity and Selectivity of Allylic Tin Reagents/n-BuLi
Under activation with n-BuLi, trialkylstannanes containing crotyl-, geranyl-, and phenyldienylmethyl appendages were reacted with efficiency and selectivity to various ketone and enone electrophiles with low reactivity. The straightforward process gives access to tertiary alcohols that are vicinal to quaternary carbons. With α,α′-dimethoxy-γ-pyrone, on the other hand, the grafting of a dienyl side chain was effected to prepare dienyl α′-methoxy-γ-pyrone in a stereo- and regioselective and convergent manner. Furthermore, the advantages of this route were highlighted for the preparation of organolithium species at low temperature with the formation of a minimum amount of salts. Synthetic manipulations were demonstrated to illustrate the potential of the chemistry for constructing acyclic and cyclic terpene scaffolds.
Cormier, Morgan,Ahmad, Maha,Maddaluno, Jacques,De Paolis, Micha?l
p. 4920 - 4927
(2018/02/07)

A mild method for the replacement of a hydroxyl group by halogen. 1. Scope and chemoselectivity
α-Chloro-, bromo- and iodoenamines, which are readily prepared from the corresponding isobutyramides have been found to be excellent reagents for the transformation of a wide variety of alcohols or carboxylic acids into the corresponding halides. Yields are high and conditions are very mild thus allowing for the presence of sensitive functional groups. The reagents can be easily tuned allowing therefore the selective monohalogenation of polyhydroxylated molecules. The scope and chemoselectivity of the reactions have been studied and reaction mechanisms have been proposed.
Munyemana, Fran?ois,George, Isabelle,Devos, Alain,Colens, Alain,Badarau, Eduard,Frisque-Hesbain, Anne-Marie,Loudet, Aurore,Differding, Edmond,Damien, Jean-Marie,Rémion, Jeanine,Van Uytbergen, Jacqueline,Ghosez, Léon
p. 420 - 430
(2015/12/31)

Copper-Promoted Tandem Reaction of Azobenzenes with Allyl Bromides via N=N Bond Cleavage for the Regioselective Synthesis of Quinolines
A copper-promoted tandem reaction of a variety of azobenzenes and allyl bromides via N=N bond cleavage to regioselectively construct quinoline derivatives has been developed. The azobenzenes act as not only construction units but also an oxidant for quinoline formation.
Yi, Xiangli,Xi, Chanjuan
supporting information
p. 5836 - 5839
(2015/12/11)

Enantioselective allylation of (2E,4E)-2,4-dimethylhexadienal: Synthesis of (5R,6S)-(+)-Pteroenone
Abstract Allylation, trans- and cis-crotylation of (2E,4E)-2,4-dimethylhexadienal, a representative α,β,γ,δ-unsaturated aldehyde, was carried out under different catalytic and stoichiometric conditions. The reactions catalyzed by organocatalysts TRIP-PA and N,N′-dioxides gave the best results with respect to yields, asymmetric induction, and catalyst load in comparison to other procedures. The developed methodology was applied in the enantioselective synthesis of (5R,6S)-(+)-pteroenone, a defensive metabolite (ichthyodeterrent) of the Antarctic pteropod Clione antarctica. Allylation and crotylation of an α,β,γ,δ-unsaturated aldehyde was studied under various conditions. The asymmetric induction was as high as 96 % ee. The anti-crotylation product was used as the crucial intermediate for the enantioselective synthesis of (5R,6S)-(+)-pteroenone, a defensive metabolite of Clione Antarctica.
Koukal, Petr,Kotora, Martin
supporting information
p. 7408 - 7412
(2015/05/13)

δ-deuterium isotope effects as probes for transition-state structures of isoprenoid substrates
The biosynthetic pathways to isoprenoid compounds involve transfer of the prenyl moiety in allylic diphosphates to electron-rich (nucleophilic) acceptors. The acceptors can be many types of nucleophiles, while the allylic diphosphates only differ in the number of isoprene units and stereochemistry of the double bonds in the hydrocarbon moieties. Because of the wide range of nucleophilicities of naturally occurring acceptors, the mechanism for prenyltransfer reactions may be dissociative or associative with early to late transition states. We have measured δ-secondary kinetic isotope effects operating through four bonds for substitution reactions with dimethylallyl derivatives bearing deuterated methyl groups at the distal (C3) carbon atom in the double bond under dissociative and associative conditions. Computational studies with density functional theory indicate that the magnitudes of the isotope effects correlate with the extent of bond formation between the allylic moiety and the electron-rich acceptor in the transition state for alkylation and provide insights into the structures of the transition states for associative and dissociative alkylation reactions.
Choi, Seoung-Ryoung,Breugst, Martin,Houk, Kendall N.,Poulter, C. Dale
supporting information
p. 3572 - 3580
(2014/05/06)

Synthesis of 3-aza-bicyclo[3.1.0]hexan-2-one derivatives via gold-catalyzed oxidative cyclopropanation of N -allylynamides
N-Allylynamides with various functional groups and different substitution patterns can be converted into 3-aza-bicyclo[3.1.0]hexan-2-one derivatives in moderate to high yield using IMesAuCl/AgBF4 as the catalyst and pyridine N-oxide as the oxidant. A noncarbene mediated approach is proposed as the mechanism.
Wang, Kai-Bing,Ran, Rui-Qiao,Xiu, Shi-Dong,Li, Chuan-Ying
supporting information
p. 2374 - 2377
(2013/06/27)

Intermolecular oxonium ylide mediated synthesis of medium-sized oxacycles
Detailed in this account are our efforts toward efficient oxacycle syntheses. Two complementary approaches are discussed, with both employing chemoselective allyl ether activation and rearrangement as the key step. Vinyl substituted oxiranes and oxetanes provide a single step access to dihydropyrans and tetrahydrooxepines. Oxiranes proved to be poor substrates, while oxetanes were slightly better. An alternative approach using substituted allyl ethers proved successful and addressed the limitations encountered in the ring expansions.
MacK, Daniel J.,Batory, Lindsay A.,Njardarson, Jon T.
supporting information; body text
p. 378 - 381
(2012/03/09)

Total synthesis of infectopyrone, aplysiopsenes A-C, ent-aplysiopsene D, phomapyrones A and D, 8,9-dehydroxylarone, and nectriapyrone
The total synthesis of the 2-pyrone natural products nectriapyrone, aplysiopsenes A-C, ent-aplysiopsene D, phomapyrones A and D, and of 8,9-dehydroxylarone were achieved by Wittig olefination starting with vermopyrone. Infectopyrone was synthesized by Horner-Wadsworth-Emmons reaction starting with phomapyrone D. Racemic phomapyrone C methyl ether was obtained by hydrogenation of nectriapyrone. The total syntheses were achieved starting from commercially available 3,5-heptanedione and led to the desired natural products in 18-46% over 5-6 steps, whereupon all five-step syntheses were carried out with a single chromatographic workup. The total synthesis of infectopyrone, aplysiopsenes A-D, of phomapyrones A and D, and of 8,9-dehydroxylarone were achieved for the first time, giving unambiguous proof for the proposed structures of these natural products.
Geiseler, Oliver,Podlech, Joachim
experimental part
p. 7280 - 7287
(2012/09/11)

Aromatic cations from oxidative carbon-hydrogen bond cleavage in bimolecular carbon-carbon bond forming reactions
Chromenes and isochromenes react quickly with 2,3-dichloro-5,6-dicyano-1,4- benzoquinone (DDQ) to form persistent aromatic oxocarbenium ions through oxidative carbon-hydrogen cleavage. This process is tolerant of electron-donating and electron-withdrawing groups on the benzene ring and additional substitution on the pyran ring. A variety of nucleophiles can be added to these cations to generate a diverse set of structures.
Clausen, Dane J.,Floreancig, Paul E.
experimental part
p. 6574 - 6582
(2012/10/08)

Catalytic phosphorus(V)-mediated nucleophilic substitution reactions: Development of a catalytic appel reaction
Catalytic phosphorus(V)-mediated chlorination and bromination reactions of alcohols have been developed. The new reactions constitute a catalytic version of the classical Appel halogenation reaction. In these new reactions oxalyl chloride is used as a consumable stoichiometric reagent to generate the halophosphonium salts responsible for halogenation from catalytic phosphine oxides. Thus, phosphine oxides have been transformed from stoichiometric waste products into catalysts and a new concept for catalytic phosphorus-based activation and nucleophilic substitution of alcohols has been validated. The present study has focused on a full exploration of the scope and limitations of phosphine oxide catalyzed chlorination reactions as well as the development of the analogous bromination reactions. Further mechanistic studies, including density functional theory calculations on proposed intermediates of the catalytic cycle, are consistent with a catalytic cycle involving halo- and alkoxyphosphonium salts as intermediates.
Denton, Ross M.,An, Jie,Adeniran, Beatrice,Blake, Alexander J.,Lewis, William,Poulton, Andrew M.
experimental part
p. 6749 - 6767
(2011/10/02)

Regioselective hydroformylation of sulfonamides using a scaffolding ligand
A highly regloselectlve hydroformylatlon of allyllc sulfonamides has been developed by employing a catalytic directing group. The reaction tolerates a wide range of electronically and sterlcally modified olefins, and only 10% of the scaffolding llgand Is required to effectively control the regloselectlvlty.
Worthy, Amanda D.,Gagnon, Morlah M.,Dombrowski, Michael T.,Tan, Kian L.
supporting information; scheme or table
p. 2764 - 2767
(2009/11/30)

An acyl-claisen approach to tetrasubstituted tetrahydrofuran lignans: Synthesis of fragransin A2, talaumidin, and lignan analogues
A simple and stereocontrolled synthesis of racemic 2,3,4,5-tetrasubstituted tetrahydrofurans was achieved from acyl-Claisen derived syn-disubstituted amides. Georg Thieme Verlag Stuttgart New York.
Rye, Claire E.,Barker, David
experimental part
p. 3315 - 3319
(2010/03/04)

Phase-Vanishing Methodology for Efficient Bromination, Alkylation, Epoxidation, and Oxidation Reactions of Organic Substrates
(Matrix presented) In cases where both reactants in a phase-vanishing reaction are less dense than the fluorous phase, an alternative to the U-tube method is to employ a solvent with greater density than the fluorous phase, such as 1,2-dibromoethane. This modification has been successfully applied to the methylation of a phenol derivative with dimethyl sulfate and to the m-CPBA-induced epoxidation of alkenes, N-oxide formation from nitrogen-containing compounds, and S-oxide or sulfone formation from organic sulfides.
Jana, Nirmal K.,Verkade, John G.
p. 3787 - 3790
(2007/10/03)

Synthesis and self-photooxygenation of alkenyl-linked [60]fullerene derivatives. A regioselective ene reaction
(equation presented) Alkenyl-linked C60 derivatives undergo self-photooxygenation regioselectively, by the preferential abstraction of allylic hydrogens on the fullerene side of the double bond.
Chronakis, Nikos,Vougioukalakis, Georgios C.,Orfanopoulos, Michael
p. 945 - 948
(2007/10/03)

Reaction of metallated tert-butyl(phenyl)phosphane oxide with electrophiles as a route to functionalized tertiary phosphane oxides: Alkylation reactions
P-Chiral tertiary phosphane oxides have been prepared from each of the secondary phosphane oxides racemic 1, (S(p))-(-)-4 and (Rp)-(+)-tert-butylphenylphosphane oxide (5) by lithiation with LDA or nBuLi, or sodiation with sodium hydride, in THF, and then by treatment with a series of primary alkyl halides. Doubly P-chiral ditertiary bis(phosphane oxides) are also obtained from these metallated secondary phosphane oxides by treatment with electrophiles based on straight-chain, tartrate-derived, and bishalomethylarene dihalides. In general, the bis-phosphane oxides are obtained in good yields. However, when the α,ω-dihalide bears an embedded heteroatom (O or Si), yields are diminished. The enantiomeric purity of each of the products was assessed through admixture with (R(p))- and (S(p))-tert-butyl(phenyl)phosphanylthioic acids and measurement of the tert-butyl resonances in the 1H-NMR spectra. In all cases, the act of metallation of the enantiomerically pure secondary phosphane oxide followed by its alkylation is not accompanied by detectable racemization. This method for preparing P-chiral tertiary phosphane oxides is therefore more straightforward than those described previously.
Haynes, Richard K.,Au-Yeung, Tin-Lok,Chan, Wai-Kuen,Lam, Wai-Lun,Li, Zhi-Yi,Yeung, Lam-Lung,Chan, Albert S. C.,Li, Pauline,Koen, Mark,Mitchell, Craig R.,Vonwiller, Simone C.
p. 3205 - 3216
(2007/10/03)

Peptidyl inhibitors of viral proteases
The invention provides amino acid derivatives of the formula STR1 wherein E represents CHO or B(OH)2 ; R1 represents lower alkyl (optionally substituted by halo, cyano, lower alkylthio, aryl-lower alkylthio, aryl or heteroaryl), lower alkenyl or lower alkynyl; R2 represents lower alkyl optionally substituted by hydroxy, carboxy, aryl, aminocarbonyl or lower cycloalkyl; and R3 represents hydrogen or lower alkyl; or R2 and R3 together represent di- or trimethylene optionally substituted by hydroxy; R4 represents lower alkyl (optionally substituted by hydroxy, lower cycloalkyl, carboxy, aryl, lower alkylthio, cyano-lower alkylthio or aryl-lower alkylthio), lower alkenyl, aryl or lower cycloalkyl; R5 represents lower alkyl (optionally substituted by hydroxy, lower alkylthio, aryl, aryl-lower alkylthio or cyano-lower alkylthio) or lower cycloalkyl; R6 represents hydrogen or lower alkyl; R7 represent lower alkyl (optionally substituted by hydroxy, carboxy, aryl or lower cycloalkyl) or lower cycloalkyl; R8 represents lower alkyl optionally substituted by hydroxy, carboxy or aryl; and R9 represents lower alkylcarbonyl, carboxy-lower alkylcarbonyl, arylcarbonyl, lower alkylsulphonyl, arylsulphonyl, lower alkoxycarbonyl or aryl-lower al koxycarbonyl, and salts of acidic compounds of formula I with bases, which are viral proteinase inhibitors useful as antiviral agents, especially for the treatment or prophylaxis of infections caused by Hepatitis C, Hepatitis G and human GB viruses.
-
(2008/06/13)

The thermal desulfination of allylic sulfonyl halides
Allylic sulfonyl halides can be generated by halogenolysis of the corresponding triorganotin sulfinates. Allylic sulfonyl bromides and iodides undergo a first order, thermal desulfination with allylic rearrangement to yield the corresponding allylic halides. The desulfination of a cyclic allylic sulfonyl bromide is stereospecific, proceeding with γ-syn bromine migration.
King, Malcolm D.,Sue, Rodney E.,White, Rodney H.,Young, David J.
p. 4493 - 4496
(2007/10/03)

(Phenylsulfonyl)allenes as substrates for cycloaddition reactions: Intramolecular cyclizations onto unactivated alkenes
The reaction of a series of allyl-substituted bis(phenylsulfonyl)methanes or dimethyl malonates with 2,3-bis(phenylsulfonyl)-1,3-butadiene in the presence of base afforded alkenyl-substituted allenes in good yield. The reaction proceeds by initial attack of the soft carbanion onto the terminal position of the diene, and this is followed by PhSO2- elimination to give the phenylsulfonyl-substituted allene. Themal [2 + 2]-cycloaddition proceeded across the C1-C2 double bond of the allene with completely sterospecificity. Stepwise bonding prefers to occur in a 1,6-exo manner rather than in a 1,7-endo fashion. Substitution at the 7-position of the π-bond causes a crossover in the regioselectivity of the [2 + 2]-cycloaddition process. All products can be rationalized by a mechanism which includes an initial carbon-carbon bond formation involving the central allene carbon to give a diradical intermediate. The product distribution is then determined by the substitution pattern of the alkene and the fate of the diradical intermediate.
Padwa, Albert,Meske, Michael,Murphree, S. Shaun,Watterson, Scott H.,Ni, Zhijie
p. 7071 - 7080
(2007/10/02)

Preparation of Some Novel Butyl, Butenyl, Butadienyl and Bytynyl Sulfone Electrophiles for Use in Enolate Trapping Studies
The preparation of some novel four-carbon electrophiles and electrophile intermediates is described.Thus, the chlorobutenyl sulfone (5), the iodobutynyl sulfone (6) and the hitherto unreported chlorobutynyl sulfone (4) were prepared.The novel intermediates, containing a chelating imidazolyl functionality, the N-methylimidazolyl sulfides (13)-(15) were also prepared.However, they polymerized rapidly, thus preventing further synthetic manipulations.The preparation of the α-(trimethylsilyl)butadienyl sulfones (17) and (18) is described and the mode of formation of the intermediate α-trimethylsilyl sulfides (21) and (22) from the trimethylsilylbutenyl sulfide (27) is discussed.
Loughlin, Wendy A.,Haynes, Richard K.
p. 651 - 662
(2007/10/02)

A 1H and 13C NMR Study of the Structure of Sulfur-Stabilized Lithiated Allylic Carbanions
NMR studies of the solution structures of lithiated (E)-1-(t-butylthio)but-2-ene (4) and lithiated (E)-1-(phenylthio)but-2-ene (6) are reported.The structure of lithiated (E)-1-(t-butylthio)but-2-ene (4) is best described as a transoid carbanion with the allylic carbons C1, C2, and C3 having intermediate sp2-sp3 hybridization.In (4) the heteroatom and non-allylic substituent do not play any significant role in carbanion stabilization.Lithiated (E)-1-(phenylthio)but-2-ene (6) differs from (4) in that it exhibits cis geometry about the C1-C2 bond and the phenylthio group participates in helping to stabilize allylic charge.There is a discrepancy between the geometry about the C1-C2 bond in the solution and solid structures of (4) in the presence of TMEDA.
Glendenning, Lionel,Field, Leslie D.,Haynes, Richard K.
p. 2739 - 2750
(2007/10/03)

Stereospecific Synthesis of 2,3,6-Trisubstituted Piperidines: An Efficient Total Synthesis of (+/-)-Pumiliotoxin C
The intramolecular cycloaddition of N-(1-alkyl-4-pentenyl)nitrones provides a highly regio- and stereoselective route to all-cis-2,6-disubstituted-3-(hydroxymethyl)piperidines 3 by way of the bicyclic isoxazolidines 2.In demonstration studies, the 2,6-dimethyl analogue was transformed into 2r,3c,6c-trimethylpiperidine (9) and into N-tert-butoxy-2c,6c-dimethylpiperidine-3r-carboxaldehyde (10).Facile and complete epimerization of the latter into the all-equatorial, 2t,3r,6t aldehyde 11 was achieved, thus giving entry into the diastereomeric 2,3,6-trisubstitutedpiperidines.These protocols can give rise to short and efficient syntheses not only of the piperidines but of bicyclic nitrogen heterocycles depending on the nature of the substituents.An additional stereogenic center was introduced into the 3-(1-hydroxyalkyl) side chain by employing trans and cis isomers of N-(1,5-disubstituted-4-pentenyl)nitrones.The methodology was used to rapidly assemble a piperidine containing four stereogenic centers starting from 2-pentanone and methyl phenyl ketone.This intermediate 20 was then easily converted into (+/-)-pumiliotoxin C (12) by way of an intramolecular alkylation with inversion of configuration.The highly convergent total synthesis was accomplished in 14 steps and 14percent overall yield with no attempt at optimization.
LeBel, Norman A.,Balasubramanian, N.
p. 3363 - 3368
(2007/10/02)

Stereoselective Preparation of Bicyclooctanones from the Products of Aprotic Conjugate Addition of Lithiated Allylic Sulfoxides to Cyclopent-2-enone and Enolate Trapping with Methyl Cyanoformate
The lithium enolates arising by aprotic conjugate addition of lithiated but-2-enyl sulfoxides and a phosphine oxide to cyclopent-2-enone react efficiently with methyl cyanoformate to give the corresponding methyl 5-oxocyclopentanecarboxylates in good yields.The sulfoxides are smoothly deoxygenated with tributylphosphine diiodide in ether at 0 deg, and the resulting sulfides undergo intramolecular cyclization in the presence of tin(IV) chloride to give methyl oxobicyclooctanecarboxylates, again in good to excellent yields.The cyclizations are highly stereoselective in that the syn- and anti-stereochemistries of the enolate trapped products obtained from (E)- and (Z)-sulfoxides are quantitatively reflected in the products obtained from the cyclization reactions.
Haynes, Richard K.,Katsifis, Andrew, G.
p. 1455 - 1472
(2007/10/02)

SYNTHESIS OF ALKYL HALIDES UNDER NEUTRAL CONDITIONS
Primary and secondary alcohols are efficiently converted to the corresponding alkyl halides under neutral conditions.
Munyemana, Francois,Frisque-Hesbain, Anne-Marie,Devos, Alain,Ghosez, Leon
p. 3077 - 3080
(2007/10/02)

SYNTHESIS OF THE SEX PHEROMONE OF THE GRAIN MOTH Ephestia Elutella
A most convenient synthesis of tetradeca-9Z,12E-dien-1-ol and its acetate - components of the sex pheromone of the grain moth - has been carried out on the basis of a scheme for obtaining a cis-1,trans-4-dienic system.
Kasymzhanova, M.,Abdukakharov, V. S.,Kamaev, F. G.,Abduvakhabov, A. A.
p. 708 - 713
(2007/10/02)

Isolation of the First Allylic Gold(III) Complex Having a Triphenylphosphine Ligand
A metathetical reaction of cis-dimethyliodo(triphenylphosphine)gold(III) with 1-methylallyl Grignard reagent in ether at 0 deg C gives cis-dimethyl(η1-E-crotyl)(triphenylphosphine)gold(III), 1.Reactions of 1 with HCl and bromine give selectively 1-butene and 1-methylallyl bromide, respectively.
Komiya, Sanshiro,Ozaki, Satoshi
p. 1431 - 1432
(2007/10/02)

CONVERSION OF ALCOHOLS INTO ALKYL BROMIDES AND IODINES VIA O-ALKYLISOUREAS
Treatment of O-alkylisoureas with trifluoromethanesulphonic acid and a tetrabutylammonium salt (bromide or iodide) affords alkyl halides in high yields.
Collingwood, Stephen P,Davies, Alan P,Golding, Bernard T
p. 4445 - 4448
(2007/10/02)

SYNTHESIS WITH SULFONES XLIV. STEREOSELECTIVE PREPARATION OF EE 1,3-DIENES BY ELIMINATION OF BENZENESULFINIC ACID FROM E HOMOALLYLIC SULFONES.
The preparation of pure E and Z homoallylic 1,1-disulfones followed by the stereoselective reduction of one sulfonyl moiety afforded pure E and Z homoallylic sulfones respectively.Basic elimination with tBuOK in THF gave the corresponding 1,3-dienes in good yield.This reaction, highly stereoselective in the case of E homoallylic sulfones, has been used in the synthesis of (8E,10E) 8,10-dodecadienol, 10 and (9E)9,11-dodecadienol, 15, insect pheromone components.
Penhoat, C. Herve Du,Julia, M.
p. 4807 - 4816
(2007/10/02)

Unsaturated compounds and their preparation
Unsaturated compounds of the formula: STR1 in which: Q denotes alkyloxycarbonyl, cyano or formyl, R1 denotes a saturated or unsaturated aliphatic radical, R2 denotes a hydrogen atom or an alkyl radical, R3 denotes a hydrogen atom or an aliphatic radical and R4 denotes a hydrogen atom or a saturated or unsaturated aliphatic radical which may be substituted, are useful as intermediates in the synthesis of vitamin E.
-
(2008/06/13)

ELECTROPHILIC SUBSTITUTION OF STRUCTURALLY RIGID n1-ALLYLPALLADIUM COMPLEXES
h1-Allyl(aryl)palladium complexes react with some electrophiles to result in the selective Pd-allyl bond cleavage with 1,3-transposition, while the corresponding η3-allyl(aryl)palladiums and the electrophiles give rise to the selective Pd-Ar bond cleavage.The η1-allyl complexes also react with CCl4 and CHCl3 under very mild conditions to give good yields of CH2=CHCHR(CR'Cl2) (R=H, Me; R'=Cl, H).
Kurosawa, Hideo,Urabe, Akira
p. 1839 - 1840
(2007/10/02)

BORON TRIFLUORIDE ETHERATE/HALIDE ION, A NOVEL REAGENT FOR THE CONVERSION OF ALLYL, BENZYL AND TERTIARY ALCOHOLS TO THE HALIDES
A combination of boron trifluoride etherate and halide ion is found to be an excellent reagent for the conversion of allyl, benzyl and tertiary alcohols to the halides.
Mandal, Arun K.,Mahajan, S. W.
p. 3863 - 3866
(2007/10/02)

A reinvestigation of the vapor phase bromination of 2-bromobutane
The soltuion phase photobromination of 2-bromobutane yields 2,2-dibromobutane, meso-2,3-dibromobutane, dl-2,3-dibromo-dibromobutane, small amounts of 1,2-dibromobutane, and 2,2,3-tribromobutane.However, in the corresponding vapor phase bromination these products appear along with other polybrominated products.The yield of these polybromides increases with temperature.The increase in yield of the polyhalogenated materials is rationalized by considering the thermal instabilty of the β-bromoalkyl radical, which eliminates a bromine atom to form the corresponding alkene.It is demonstrated that in the vapor phase allylic bromination competes succesfully with bromine addition.Reaction schemes are suggested to explain the formation of polybromides.An explanation is also offered for the dicrepancy between these results and those of previously reported vapor phase work.
Tanner, Dennis D.,Ruo, Tomoki C. S.,Kosugi, Yoshio,Potter, Alan
p. 2310 - 2316
(2007/10/02)

Interhalogen-Catalyzed Cleavages of Ethers and Esters with Trimethylsilyl Bromide or Chloride
The cleavages of various dialkyl ethers, trimethylsilyl alkyl ethers, and alkyl esters by trimethylsilyl bromide are strongly catalyzed by iodine monobromide.This catalyzed cleavage procedure using iodine monobromide makes possible synthetic applications for trimethylsilyl bromide which were previously ruled out by problems with its low reactivity.Cleavages of benzylic and tertiary alkyl ethers and esters by trimethylsilyl chloride are feasible when catalyzed by iodine monochloride.However, other systems are essentially unreactive toward trimethylsilyl chloride even in the presence of iodine monochloride.
Friedrich, Edwin C.,DeLucca, George
p. 1678 - 1682
(2007/10/02)

Diastereoselective α Allylation of Secondary and Tertiary Thioamides via Thio-Claisen Rearrangement. A Structural Proof of Z Secondary Thioamide Dianions and Z Tertiary Thioamide Anions
Highly diastereoselective α allylation of secondary and tertiary thioamides is achieved by making use of thio-Claisen rearrangement.From the correlation between the diastereoselectivities in products and the structures of allylating agents, the Z structures of secondary thioamide dianion (ca. 100percent Z) and tertiary thioamide anion (>97percent Z) are concluded.
Tamaru, Y.,Furukawa, Y.,Mizutani, M.,Kitao, O.,Yoshida, Z.
p. 3631 - 3639
(2007/10/02)

Process for production of 2,6-di-tert-alkenyl phenols
There is disclosed a process for the production of 2,6-di-tert-alkyl-4-alkenyl phenols wherein the improvement comprises the reaction of a 2,6-di-tert-alkyl phenol with an allyl halide to yield the 2,6-di-tert-alkyl-4-alkenyl phenol through the use of a triphase or polymer bound catalyst.
-
(2008/06/13)