- Radical reactions of epoxy esters induced by titanocene chloride
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The reductive radical cyclizations of several epoxy esters have been achieved using titanocene chloride. The tether length from the initial radical to the carbonyl acceptor is the key of the reactions. We obtained products from radical cyclization onto carbonyl formate and products from formate and hydrogen elimination. The stereochemical outcome of the 5-exo radical cyclization of two diastereomers is reported. A radical cascade cyclization of an unsaturated epoxy formate is also described.
- Fernández-Mateos,Herrero Teijón,Rabanedo Clemente,Rubio González
-
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Read Online
- Annulation-retro-Claisen cascade of bifunctional peroxides for the synthesis of lactone natural products
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A new and highly efficient annulation-retro-Claisen cascade, which involves the [4 + 1] or [5 + 1] annulation of α-benzoylacetates with bielectrophilic peroxides and a subsequent debenzoylation process under mild basic conditions, has been developed for the rapid construction of valuable tetrahydrofuran- and dihydropyran-2-carboxylates in good yields. By employing the new reaction, the unified total synthesis of γ- and δ-lactone natural products such as (±)-tanikolide, (±)-goniothalamins, (±)-7-epi-goniodiol, and (±)-plakolide A has been accomplished in 4-7 steps.
- Hu, Lin,Li, Jialin,Li, Xuemin,Xu, Qianlan
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supporting information
p. 274 - 277
(2022/01/03)
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- Silica-coated Fe3O4 magnetic nanoparticles-supported sulfonic acid as a highly active and reusable catalyst in chemoselective deprotection of tert-butyldimethylsilyl (TBDMS) ethers
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Anchored propyl sulfonic acid on the surface of silica-coated magnetic nanoparticles (Fe3O4@SiO2@PrSO3H) was successfully employed in the deprotection of TBDMS ethers. The prepared magnetically separable nanocatalyst exhibited efficient catalytic activity with high conversion and selectivity in cleavage of TBDMS ethers. TBDMS ethers are efficiently cleaved to the corresponding hydroxyl compounds in methanol solution containing 2 mol% magnetic nano-catalysts. Good to excellent yields of products, simple work-up and product separation, selective cleavage of TBDMS ethers in the presence of TBDPS ethers, easy recycling of the catalyst with external magnet with no loss in its activity (7 reaction cycles) are important features of this new protocol.
- Hossein Javadi, Sayed,Zareyee, Daryoush,Monfared, Azam,Didehban, Khadijeh,Mirshokraee, Sayed Ahmmad
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supporting information
p. 7 - 12
(2019/11/03)
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- Ruthenium-Catalyzed Direct Dehydrogenative Cross-Coupling of Allyl Alcohols and Acrylates: Application to Total Synthesis of Hydroxy β-Sanshool, ZP-Amide I, and Chondrillin
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Ru-catalyzed oxidative coupling of allyl alcohols and activated olefins has been developed by C(allyl)-H activation of allyl alcohols providing efficient and direct access to synthetically useful α,β-unsaturated enone intermediates. Synthetic utility of this method was demonstrated by its application to synthesis of bioactive natural products such as Hydroxy-β-sanshool, ZP-amide I, Chondrillin, Plakorin, and (+)-cis-Solamin A.
- Dethe, Dattatraya H.,Nagabhushana, C. B.
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supporting information
(2020/02/15)
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- β-Borylation of conjugated carbonyl compounds with silylborane or bis(pinacolato)diboron catalyzed by Au nanoparticles
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Conjugated aldehydes and ketones undergo reaction with Me2PhSiBpin (pin: pinacolato) catalyzed by Au nanoparticles supported on TiO2 forming exclusively the β-borylation products, via the intermediate formation of the labile silaboration adducts. This chemoselectivity pathway is complementary to the so far known analogous reaction catalyzed by other metals, where β-silylation occurs instead. β-Borylation also occurs with pinBBpin under identical reaction conditions in a variety of conjugated carbonyl compounds, including esters and amides which are unreactive in their attempted Au-catalyzed silaboration. This journal is
- Fragkiadakis, Michael,Kidonakis, Marios,Stratakis, Manolis
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supporting information
p. 8921 - 8927
(2020/11/23)
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- Enantioselective addition of selenosulfonates to α,β-unsaturated ketones
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An organo-catalyzed enantioselective addition of selenosulfonates to α,β-unsaturated ketones was developed for the first time. With a chiral squaramide as an efficient catalyst, the desired α-selenylated ketones were obtained in a good yields with high enantioselectivity up to 89% ee, and good results could be obtained on a gram scale. The products could also be efficiently transformed into useful building blocks with a propenylic stereocenter; the strategy presented in this study may find further applications in organic synthesis.
- Luo, Shilong,Zhang, Nan,Wang, Zhen,Yan, Hailong
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supporting information
p. 2893 - 2901
(2018/05/03)
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- Iron-Catalyzed Grignard Cross-Couplings with Allylic Methyl Ethers or Allylic Trimethylsilyl Ethers
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We have found that cross-coupling between aryl Grignard reagents and allylic methyl ethers proceeded well in the presence of a catalytic amounts of Fe(acac) 3 to afford the corresponding allylic substitution products in good yields. Under the same conditions, allylic trimethylsilyl ethers also reacted with Grignard reagents to give the corresponding cross-coupling products.
- Seto, Chika,Otsuka, Takeshi,Takeuchi, Yoshiki,Tabuchi, Daichi,Nagano, Takashi
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supporting information
p. 1211 - 1214
(2018/03/26)
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- One-Pot Transformation of Simple Furans into Octahydroindole Scaffolds
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A highly efficient and general singlet-oxygen-initiated one-pot transformation of readily accessible furans into octahydroindole scaffolds has been developed.
- Kalaitzakis, Dimitris,Triantafyllakis, Myron,Ioannou, Georgios I.,Vassilikogiannakis, Georgios
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supporting information
p. 4020 - 4023
(2017/03/27)
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- Highly efficient kinetic resolution of allylic alcohols with terminal double bond
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In this study, the lipase-catalyzed kinetic resolution (Novozyme 435) was employed to prepare chiral allylic alcohols and acetates with terminal double bonds in enantiomeric excesses ranging from 94 to >99 %.
- Marques, Francisco A.,Oliveira, Marcos A.,Frensch, Gustavo,Sales Maia, Beatriz Helena L. N.,Barison, Andersson,Lenz, Cesar A.,Guerrero Jr., Palimecio G.
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experimental part
p. 696 - 700
(2012/06/04)
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- Titanocene-promoted eliminations on epoxy alcohols and epoxy esters
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The reaction of a series of 2,3-epoxy alcohols and the corresponding formates, acetates, and benzoates promoted by Cp2TiCl has been studied. The different outcome of the reaction of epoxy derivatives has been rationalized in terms of mechanistically biased processes. After homolytic oxirane cleavage, four main types of reaction were found: dehydroxylation, decarboxylation, dehydrogenation, and deoxygenation. The reaction products varied according to the substitution pattern. The radical nature of these eliminations is demonstrated.
- Fernandez-Mateos, Alfonso,Madrazo, Soledad Encinas,Teijon, Pablo Herrero,Gonzalez, Rosa Rubio
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experimental part
p. 856 - 861
(2010/04/05)
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- Copper-catalyzed rearrangement of vinyl oxiranes
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A novel copper-catalyzed vinyl oxirane ring expansion protocol has been developed. A wide range of vinyl oxiranes can be rearranged to 2,5-dihydrofurans in excellent yields in the presence of electrophilic copper(II) acetylacetonate catalysts. Regioisomeric vinyl oxiranes can be converted to a single dihydrofuran product using these conditions. This method uses low catalyst loadings (0.5-5 mol %), has good tolerance of substitution patterns, and can be done in the absence of solvent. Copyright
- Batory, Lindsay A.,McInnis, Christine E.,Njardarson, Jon T.
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p. 16054 - 16055
(2007/10/03)
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- A high loading sulfonic acid-functionalized ordered nanoporous silica as an efficient and recyclable catalyst for chemoselective deprotection of tert-butyldimethylsilyl ethers
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A high loading sulfonic acid-functionalized ordered nanoporous silica efficiently catalyzes the deprotection of a variety of alcoholic TBDMS (tert-butyldimethylsilyl)ethers in methanol. The catalyst shows high thermal stability (up to 240°C) and can be recovered and reused for at least seven reaction cycles without loss of reactivity. This method can be used to deprotect TBDMS ethers of alcohols in the presence of TBDMS ethers of phenols.
- Karimi, Babak,Zareyee, Daryoush
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p. 4661 - 4665
(2007/10/03)
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- Vanadium-catalyzed selenide oxidation with in situ [2,3] sigmatropic rearrangement (SOS reaction): Scope and asymmetric applications
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A vanadium-catalyzed method for the oxidation of prochiral aryl, allylic selenides with tandem sigmatropic rearrangement has been developed. This protocol has been screened on a series of substrates to test for its generality and effectiveness. The applicability of this methodology to the synthesis of enantiomerically enriched allylic alcohols has been studied on a series of chiral oxazole-containing systems with a diastereomeric ratio (d.r.) of up to 85 : 15. The chiral transfer observed in the allyl alcohol products is the result of a net 1,9- and/or 1,10-induction. Finally, the first example of a selenium-oxygen nonbonding interaction in oxazole-containing selenide appears to have been observed via X-ray crystal analysis.
- Campbell Bourland,Carter, Rich G.,Yokochi, Alexandre F. T.
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p. 1315 - 1329
(2007/10/03)
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- Desilylation and conversion of trimethylsilylmethyl epoxides into ketones under the influence of a bulky base
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Trimethylsilylmethyl epoxides were converted into ketones through a desilylation, epoxide ring-opening, and rearrangement reaction under the influence of a bulky base in the presence of 18-crown-6.
- Ma, Yuan
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p. 310 - 315
(2007/10/03)
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- Facile O-deallylation of allyl ethers via SN2′ reaction with tert-butyllithium
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(Formula presented) Allylic ethers are converted to the corresponding alcohol or phenol in virtually quantitative yield at temperatures below ambient simply by stirring a hydrocarbon solution of the ether with 1 molar equiv of tert-butyllithium. The reaction, which produces 4,4-dimethyl-1-pentene as a coproduct, most likely involves an SN2′ attack of the organolithium on the allyl ether.
- Bailey, William F.,England, Michael D.,Mealy, Michael J.,Thongsornkleeb, Charnsak,Teng, Lisa
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p. 489 - 491
(2007/10/03)
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- The first vanadium-catalyzed oxidation of aryl allylic selenides with in situ [2,3] sigmatropic rearrangement
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The efficient synthesis of a series of 2°allylic alcohols from a vanadium-catalyzed oxidation of suitably disposed allylic selenides with tandem [2,3] sigmatropic rearrangement is outlined.
- Carter,Bourland
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p. 2031 - 2032
(2007/10/03)
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- New stereoselective synthesis of (±)-trans-2-butyl-5-heptyl-1- methylpyrrolidine, ant venom alkaloid, by aminyl radical cyclization
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New synthesis of (±)-trans-2-butyl-5-heptyl-1-methylpyrrolidine (1), ant venom alkaloid, was achieved by the use of stereoselective cyclization of aminyl radicals. Thus, orthoester Claisen rearrangement of 1-hexen-3-ol (2) gave (E)-ethyl 4-octenoate (3). Reaction of ester (3) with 2- methylaminopyridine and AlCl3 afforded the corresponding N-methyl-N-(2- pyridyl)amide (4), which was treated with heptylmagnesium iodide at -78°C to give (E)-4-pentadecen-8-one (5). Reductive amination of ketone (5) with methylamine gave N-methyl-1-heptyl-4-octenylamine (6). Treatment of amine (6) with NCS in toluene gave the corresponding N-chloroamine (12), and successive heating under reflux with Bu3SnH and AIBN resulted in stereoselective cyclization of the aminyl radical to give (±)-trans-2-butyl-5-heptyl-1- methylpyrrolidine (1) in a 59percent yield. Similarly, 1-nonen-3-ol (7) was converted into N-methyl-1-butyl-4-undecenylamine (11), which was subjected to the aminyl radical cyclization to give 1 in a 49percent yield.
- Senboku, Hisanori,Hasegawa, Hikaru,Orito, Kazuhiko,Tokuda, Masao
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p. 333 - 340
(2007/10/03)
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- Synthesis and Applications of Tetrahydrofuran-Stable Substituted (3-Lithioxyalkyl)- and (4-Lithioxyalkyl)lithiums, Modified with Magnesium 2-Ethoxyethoxide
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Substituted hydroxyalkyl phenyl sulfides 3 have been synthesized from the corresponding allylic or homoallylic alcohols 2. Regiospecific cleavage of the C - SPh bond of the sulfides 3 by lithium dispersion in tetrahydrofuran (THF) led to the synthesis of substituted (3-lithioxyalkyl)- and (4-lithioxyalkyl)lithiums 4, most of which share the ω carbon with a carbocyclic ring. The organolithiums were modified with magnesium 2-ethoxyethoxide in order to suppress their reactivity toward THF cleavage, thus offering the advantage of preparing storable ethereal solutions of certain types of (lithioxyalkyl)lithiums. This strategy appears to be of rather broad scope. The functionalized organolithiums prepared in this way react normally with electrophilic reagents with yields in the range 35-55%. Thus, carboxylations of 4 yielded lactones 5, some of which are natural products, while reactions of 4 with benzophenone and cyclic ketones yielded 1,4- and 1,5-diols 6 and 7, respectively.
- Kostas, Ioannis D.,Screttas, Constantinos G.
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p. 5575 - 5577
(2007/10/03)
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- Tellurium in the 'no-solvent' organic synthesis of allylic alcohols
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Elemental tellurium can be reduced by rongalite (HOCH2SO2Na·2H2O)-KOH in the solid phase by application of ultrasound or by microwave irradiation. Without solvent, the organic substrate leg sulfonate ester of an oxiranemethanol) is added with further sonication or irradiation to yield the desired organic product leg allylic alcohols) and elemental Te which may be recycled Phase-transfer conditions (water-toluene) also are satisfactory.
- Xu, Qinyu,Chao, Bin,Wang, Yongmei,Dittmer, Donald C.
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p. 12131 - 12146
(2007/10/03)
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- Enyne Cyclisation By Photoinduced Electron Transfer (PET) Promoted In Situ Generated Electrophilic Selenium Species: A New Carbocyclisation Strategy
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A new strategy for the carbocyclisation of enynes by PET initiated in situ generated electrophilic selenium species from diphenyldiselenide (PhSeSePh) is reported.The structure of the reactive selenium intermediate is also discussed.
- Pandey, Ganesh,Sekhar, B. B. V. Soma
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p. 1483 - 1494
(2007/10/02)
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- Highly Diastereoselective Synthesis of Substituted Epichlorohydrins and Regioselective Preparation of Allyl Alcohols using Chloro or Idomethyllithium
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Substituted epichlorohydrins 3 or 6 are obtained α-bromo or α-chlorocarbonyl compounds (1 or 4) and chloro or iodomethyllithium, respectively.Starting from α-bromocarbonyl compounds 1 or acyclic α-chloro ketones the reaction takes place with total diastereoselectivity.Treatment of epichlorohydrins 3 or 6 with lithium iodide affords the same substituted allyl alcohols 7 in a regioselective manner.A mechanism to explain this transformation is proposed.Regioisomeric allyl alcohols 11 are prepared by reaction of epichlorohydrins 6 with lithium powder.
- Concellon, Jose M.,Llavona, Lujan,Bernad, Pablo L. Jr.
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p. 5573 - 5584
(2007/10/02)
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- Allylic Alcohols by Methylene Transfer from N-Lithiomethyl-N,N',N'',N''-tetramethyldiethylenetriamine to Epoxides
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Allylic (homoallylic) alcohols are obtained from epoxides (and certain oxetanes) and N-lithiomethyl-N,N',N'',N''-tetramethyldiethylenetriamine.
- Schakel, Marius,Luitjes, Hendrikus,Dewever, Frank L. M.,Scheele, Jan,Klumpp, Gerhard W.
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p. 513 - 514
(2007/10/02)
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- Reaction of (α,β-Epoxyalkyl)silanes with α-Sulfonyl Anions and α-Sulfonyl Anions in the Presence of a Lewis Acid. A Method for the Synthesis of (Z)-sec-Allylic Alcohols and β,γ-Unsaturated Alkyl Phenyl Sulfones
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The reaction of 2-alkyl-3-(trimethylsilyl)oxiranes (1a or 1b) with anions generated from alkyl phenyl sulfones (2a-f) followed by hydrolysis affords sec-allyl alcohols 3-7.An analogous reaction in the presence of BF3*Et2O affords adducts 8-11.Treatment of 8-11 with NaOH under phase-transfer conditions affords stereospecifically the corresponding allylic alcohols 4a-5c.Reaction of oxirane 1a with anions derived from sterically hindered sulfones 2e or 2f in the presence of BF3*Et2O was investigated.Reaction of compounds 8, 9 with phosphorus tribromide in pyridine affords β,γ-unsaturated sulfones 19. - Key Words: (α,β-Epoxyalkyl)trimethylsilane reactions / α-Sulfonyl anions / Allylic alcohols / β,γ-Unsaturated alkyl phenyl sulfones
- Masnyk, Marek,Wicha, Jerzy
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p. 677 - 684
(2007/10/02)
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- A Novel Synthesis of Homologated Allylic Alcohols Using Dimethylsulphonium Methylide
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The reaction of excess dimethylsulphonium methylide with various aliphatic and aromatic ketones leads exclusively to homologated allylic alcohols in good yields.
- Harnett, J. J.,Alcaraz, L.,Mioskowski, C.,Martel, J. P.,Gall, T. Le,et al.
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p. 2009 - 2012
(2007/10/02)
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- Preparation of disubstituted epichlorohydrins with total diastereoselectivity. Transformation of α-bromocarbonyl compounds into allyl alcohols
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Epichlorohydrins 3 have been obtained with total diastereoselectivity from α-bromocarbonyl compounds and chloromethyllithium generated in situ. The treatment of compounds 3 with lithium iodide or lithium powder affords allyl alcohols 4 in a regioselective manner.
- Barluenga, Jose,Llavona, Lujan,Bernad, Pablo L.,Concellon, Jose M.
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p. 3173 - 3176
(2007/10/02)
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- A SIMPLE PROCEDURE FOR THE SYNTHESIS OF THREE-CARBON HOMOLOGATED BORONATE ESTERS AND TERMINAL ALKENES VIA NUCLEOPHILIC DISPLACEMENT IN α-HALOALLYLBORONATE ESTER
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The transfer reactions of α-haloallylboronate ester 1 with representative organolithium and Grignard reagents provide α-alkyl- or α-aryl-substituted allylboronate esters, readily converted into three-carbon homologated boronate esters and terminal alkenes.
- Brown, Herbert C.,Rangaishenvi, Milind V.
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p. 7115 - 7118
(2007/10/02)
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- BRANCHED-CHAIN DERIVATIVES OF ACYCLIC ADENOSINE ANALOGS: ALKYL AND HYDROXYMETHYL DERIVATIVES OF S-ADENOSYL-L-HOMOCYSTEINASE INHIBITORS SUBSTITUTED AT THE 2- AND 3-POSITION OF THE SIDE CHAIN
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Reaction of 1,3-dichloro-2-propanone (VII) with methylmagnesium chloride, followed by alkaline hydrolysis, afforded 2-methylpropane-1,2,3-triol (VIII) which on treatment with 2,2-dimethoxypropane and subsequent tosylation give 4-(p-toluenesulfonyloxymethyl)-2,2,4-trimethyl-1,3-dioxolane (IXb).Compound IXb was condensed with sodium salt of adenine and the intermediate X was acid-hydrolysed to give 9-(RS)-(2,3-dihydroxy-2-methylpropyl)adenine (XI).Oxidation of XI with sodium periodate led to 9-(2-oxopropyl)adenine (XII). 9-(RS)-(2-Hydroxy-2-hydroxymethyloctyl)adenine (XVI) was obtained analogously from compound VII and hexylmagnesium bromida via triol XIV.Methyl 2-bromomethyl-2-propenoate (XVII) reacted with sodium salt of adenine and the resulting methyl 2-(adenin-9-ylmethyl)-2-propenoate (XVIII) was hydroxylated with sodium perchlorate and osmium tetroxide.The obtained methyl (RS)-2-(adenin-9-ylmethyl)-2,3-dihydroxypropanoate (XIX) was alkali-hydrolysed to give sodium salt of the acid XX.Reduction of ester XIX with sodium borohydride furnished 9-(RS)-(2,3-dihydroxy-2-hydroxymethylpropyl)adenine (XXI). 1-Nonen-3-ol (XXIII), obtained by reaction of propenal with hexylmagnesium bromide, was converted by hydroxylation with osmium tetroxide into nonane-1,2,3-triol (XXIVa) and further into its 1-O-p-toluenesulfonate XXIVb which reacted with 2,2-dimethoxypropane to give 2,2-dimethyl-4-hexyl-5-(p-toluenesulfonyloxymethyl)-1,3-dioxolane (XXV).Compound XXV reacted with adenine and the resulting intermediate XXVI was converted into 9-(RS)-(2,3-dihydroxynonyl)adenine (XXVII) by acid hydrolysis. 9-(3-Methyl-2-buten-1-yl)adenine (XXVIII), obtained by alkylation of sodium salt of adenine with 1-bromo-3-methyl-2-butene, was oxidized with potassium permanganate in an acid medium to give 9-(3-hydroxy-2-oxo-3-methylbutyl)adenine (XXIX).This compound was converted into 9-(RS)-(2,3-dihydroxy-3-methylbutyl)adenine (XXX) by reduction with sodium borohydride. 4-C-Hydroxymethyl-1,2-O-isopropylidene-α-D-xylofuranose (XXXII) reacted with 2,2-dimethoxypropane under formation of 4-C-hydroxymethyl-1,2:3,5-di-O-isopropylidene derivative XXXIIIa whose p-toluenesulfonyl derivative XXXIIIb on treatment with adenine afforded 4-C-(adenin-9-yl)methyl-1,2:3,5-di-O-isopropylidene-α-D-xylofuranose (XXXIV).Acid hydrolysis of this compound, followed by oxidation in an alkaline medium, gave (2S,3R)-4-(adenin-9-yl)-3-hydroxymethyl-2,3-dihydroxybutanoic acid, isolated as its ethyl ester XXXVI.
- Holy, Antonin
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p. 248 - 265
(2007/10/02)
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- PROTIODESILYLATION REACTIONS OF β AND γ-HYDROXYSILANES: DEUTERIUM LABELING AND SILICON-DIRECTED EPOXIDE OPENINGS
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Protiodesilylation reactions of β-hydroxysilanes are catalyzed by crown ether, can be used to introduce deuterium, and can be used to prepare silicon-free products of silicon-directed epoxide openings; similar reactions of γ-hydroxysilanes are possible.
- Hudrlik, Paul F.,Holmes, Peter E.,Hudrlik, Anne M.
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p. 6395 - 6398
(2007/10/02)
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- A New Reaction in Organosilicon Chemistry: The Oxidative Ring Closure of Allylsilanes with Ceric Ammonium Nitrate
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Allylsilanes containing heteroatom nucleophiles yield cyclic products when treated with (NH4)2Ce(NO3)6.For example, hydroxy and amido-containing allylsilanes yield the corresponding tetrahydrofuran, tetrahydropyran, and piperidine analogs.These reactions and their application to natural product synthesis will be discussed.
- Wilson, Stephen R.,Augelli-Szafran, Corinne E.
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p. 3983 - 3996
(2007/10/02)
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- Alkene Epoxidation by Iodosylbenzene Catalysed by Porphyrin and Non-porphyrin Iron Complexes: the Importance of the Porphyrin Ligand in Cytochrome P-450 and Heme Model Reactions
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FeCl3 and Fe(acac)3 (acac = acetylacetonato), like Fe(TPP)(Cl) (TPP = tetraphenylporphyrinato), catalyse the epoxidation of styrene and stilbenes and the oxidation of non-1-ene by PhIO; however, several characteristics of the oxidations catalysed by non-porphyrin iron complexes, such as stereospecificity and sensitivity to dioxygen, are very different from those of the corresponding reactions catalysed by Fe(TPP)(Cl).
- Fontecave, Marc,Mansuy, Daniel
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p. 879 - 881
(2007/10/02)
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- ENANTIOSPECIFIC SYNTHESIS OF THE IMMUNOPOTENTIATORS erythro-9 (2-HYDROXY-3-NONYL) HYPOXANTHINES AND THE threo-DIASTEREOMERS.
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The title compounds were prepared enantiospecifically by kinetic resolution of (+/-) 1-nonene-3-ol via Sharpless oxidation.The products 1,2R-epoxy-nonane-3S-ol and 1-nonene-3R-ol were efficiently converted to all four stereoisomers of 2-hydroxy-3-nonylamine, which were subsequently incorporated into the target hypoxanthines to evaluate their immunopotentiating activity.
- Bessodes, M.,Abushanab, E.,Antonakis, K
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p. 5899 - 5902
(2007/10/02)
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- Regioselective Synthesis of Allyltrimethylsilanes from Allylic Halides and Allylic Sulfonates. Application to the Synthesis of 2,3-Bis(trimethylsilyl)alk-1-enes
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The preparation of allyltrimethylsilanes by regioselective pathways is described.Treatment of (E)-1-chloro-2-alkenes with a reagent prepared from 1 equiv each of trimethylsilyllithium and copper(I) iodide in hexamethylphosphoramide to presumably form a (trimethylsilyl)copper reagent affords 3-(trimethylsilyl)-1-alkenes in good to excellent yields with a high regioselectivity.Treatment of these same 1-chloro-2-alkenes with (trimethylsilyl)lithium alone without added copper(I) iodide yields only (E)-1-(trimethylsilyl)-2-alkenes.A single allylic halide thus yields two regioisomeric allyltrimethylsilanes by proper choice of reaction conditions.The reaction of a variety of allylic sulfonates with (trimethylsilyl)copper has also been investigated.The mesylates of 2 deg and 3 deg allylic alcohols yield mixtures of isomeric allyltrimethylsilanes in which the 1-(trimethylsilyl)-2-alkenes predominate.With geraniol, the mesylate was prepared in situ and allowed to react with (trimethylsilyl)copper to afford two isomeric allyltrimethylsilanes in which the 3-(trimethylsilyl)-1-alkene predominates.Finally, these reactions have also been used to prepare a variety of 2,3-bis(trimethylsilyl)alk-1-enes, a class of unsaturated organosilanes which has received little attention in the literature.
- Smith, Janice Gorzynski,Drozda, Susan E.,Petraglia, Susan P.,Quinn, Nina R.,Rice, Elizabeth M.,et al.
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p. 4112 - 4120
(2007/10/02)
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- The Synthesis of 8,10,12-Triazaprostaglandin Analogues: 1,2,4-Triazolidine-3,5-dione Derivatives
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In the search for active, more selective prostaglandin analogues, the synthesis of 8,10,12-triazaprostaglandin analogues has been achieved from readily available 4-methyl-1,2,4-triazolidine-3,5-dione.The general approach involved introduction of the α- and ω-side-chain as entire units by step-wise N-alkylation.The problems encountered with this approach of competing N- and O-mono- and di-alkylation were overcome, eventually, such that judicious choice of the initial mono-N-alkylation step enabled the synthesis of analogues incorporating wide variations in the α- and ω-side-chain.Important structural modifications included introduction of unsaturation into the α-side-chain at the 5,6-position and of methyl groups into the ω-side-chain at the 15- and 16-position as exemplified by the synthesis of 1--2-(3-hydroxy-3,4-dimethyloctyl)-4-methyl-1,2,4-triazolidine-3,5-dione (19).The stable triazaprostaglandin analogues were synthesized as racemic compounds but, nevertheless, compound (19) possessed bronchodilator activity of a similar order to that of the natural prostaglandins PGE1 and PGE2.
- Adams, David R.,Barnes, Alan F.,Cassidy, Frederick,Thompson, Mervyn
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p. 2061 - 2068
(2007/10/02)
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- SYNTHETIC ROUTES TO CYCLOPROPYLIDENECARBINOLS AND TO CYCLOPROPYLIDIENES
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Functionalized alkylidene cyclopropanes have been prepared from 1-seleno 1-vinyl cyclopropanes using (2,3) sigmatropic rearrangements of their corresponding selenoxides or selenonium ylides.A comparison with sulphur analogues is presented.
- Halazy, S.,Krief, A.
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p. 2135 - 2138
(2007/10/02)
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