Substituted epoxides by lithiation of terminal epoxides

Diamine-ligand-assisted direct hydrogen-lithium exchange allows the generation of nonstabilized (H-substituted) oxiranyllithium species and their subsequent trapping by Bu(3)SnCl and carbonyl-based electrophiles. This reaction provides a new concise route to alpha,beta-epoxystannanes and substituted epoxides.     

Enantioselective synthesis of epoxides by alpha-deprotonation--electrophile trapping of achiral epoxides

Enantioselective alpha-deprotonation of achiral epoxides 1, 21, and 26 using organolithiums in the presence of (-)-sparteine 2 and subsequent electrophile trapping gives access to enantioenriched trisubstituted epoxides 9-17, 22, 23, 27 and 28 (in up to 86% ee).     

Deoxygenation of epoxides by fluorenylidene

Irradiation of 9-diazofluorene in the presence of epoxides yields fluorenone and an equimolar concentration of the alkene formed from the stereospecific deoxygenation of the epoxide.     

Copolymerization of some epoxides by coordination-type catalysts

Copolymerizations of tritiated phenyl glycidyl ether with p- and m-methoxy, p-methyl, and p-chloro analogs, as well as with propylene oxide and epichlorohydrin are reported. The relative reactivities indicate greater Lewis acid character for triethylaluminum–water than for diethyl-zinc–water or ferric chloride–propylene oxide catalyst systems. The copolymerization of the PGE analogs is promoted by electron-donor groups and retarded by electron-withdrawing groups.     

Novel deoxygenation reaction of epoxides by indium

[reaction: see text] A novel, mild, ecofriendly protocol for the deoxygenation of epoxides to alkenes using indium metal and indium(I) chloride or ammonium chloride in alcohol has been developed. It was necessary for the presence of good radical-stabilizing groups adjacent to the oxirane ring for the deoxygenation reaction to occur. It is proposed that this reaction occurs through an SET process with indium as an electron donor.     

Single enantiomer epoxides by bromomandelation of prochiral alkenes

A combination of mandelic acid and N-bromosuccinimide efficiently converts prochiral alkenes into a readily separable 1:1 mixture of the bromomandelates. The diastereomerically pure bromomandelates are then converted into a variety of enantiomerically pure products. Terminal alkenes are converted into enantiomerically pure epoxides. Cyclohexene is converted into enantiomerically pure cis-2-azidocyclohexanol and cis-2-phenylthiocyclohexanol.     

Straightforward synthesis of thiodisaccharides by ring-opening of sugar epoxides

3,4-Anhydro hexopyranosides have been prepared by diastereoselective epoxidation of derivatives of 2-propyl 3,4-dideoxy-alpha-D-erythro-hex-3-enopyranoside (5), selectively protected at HO-2 and HO-6. The allylic group at C-2, in 5 and derivatives, plays a critical role in the facial selectivity of the epoxidation reaction. Thus, the free HO-2 in 3 (the 6-O-acetyl derivative of 5) directs the attack of m-chloroperbenzoic acid from the more hindered alpha face of the molecule to give 2-propyl 6-O-acetyl-3,4-anhydro-alpha-D-allopyranoside (7) accompanied by the beta epoxide 6 as a very minor product. Reverse diastereoselectivity has been obtained when the HO-2 in 3 was substituted by a bulky tert-butyldimethylsilyl (TBS) group. In this case, the major isomer was the 2-O-TBS derivative of 6 (alpha-D-galacto configuration). The ring-opening of sugar epoxides by nucleophilic per-O-acetyl-1-thio-beta-D-glucopyranose (11) was employed as a convenient approach to the synthesis of (1-->3)- and (1-->4)-thiodisaccharides. For example, ring-opening of the oxirane 7 by 11 led to the expected regioisomeric per-O-acetyl thiodisaccharides beta-D-Glc-S-(1-->3)-4-thio-alpha-D-Glc-O-iPr (12) and beta-D-Glc-S-(1-->4)-4-thio-alpha-D-Gul-O-iPr (13). Regioselectivity in the construction of the (1-->4)-thioglycosidic linkage could be achieved by hindering C-3 of the 3,4-anhydro sugar with a bulky silyloxy group at the vicinal C-2. For instance, coupling of the 2-O-TBS derivative of 7 with 11 led regioselectively to the protected thiodisaccharide beta-D-Glc-S-(1-->4)-4-thio-alpha-D-Glc-O-iPr (27). The utility of the approach was demonstrated through the synthesis of sulfur-linked analogues of naturally occurring (laminarabiose and cellobiose) and non-natural disaccharides (i.e., beta-D-Glc-(1-->4)-alpha-D-Gul).     

ω-氯氟烷基醇,烯烃及环氧化物的合成

本文报道在引发剂存在下, ω-氯氟烷基碘与烯丙基化合物(CH~2=CH-CH~2X, X=OH,OAC) 及乙烯基化合物CH~2=CH-OAC 发生自由基加成反应, 生成相应的加成产物Cl(CF~2)~nCH~2CHICH~2OH (2a～d), Cl(CF~2)~nCH~2CHICH~2OAC (3a～d)和Cl(CF~2)~nCH~2CHIOAC (4a～d) , 产率较好.2a～d用LiAlH~4脱碘生成Cl(CF~2)~nCH~2CH~2CH~2OH(5a～d), 反应条件温和. 2a～d与KOH-CH~3OH反应， 主要得到醇Cl(CF~2)~nCH=CHCH~2OH (6a～c), 若2a～d与NaOH-水溶液反应则得到环氧丙烷化合物. 在少量HOAC存在下， 异丙醇溶剂中， 锌粉与2a～d和3a～d反应得到消除产物Cl(CF~2)~n-CH~2CH=CH~2 (8a～d) . 4a～d与锌反应，再经KOH-CH~3OH-H~2O水解得到Cl(CF~2)~n(CH~2)~2OH(10a～d).     

Synthesis of functionally substitutedα,β-unsaturated epoxides

Conclusions A study was made of the condensation of 2,3-epoxybutyraldehyde, 2,3-epoxysuccinaldehyde mono-[dimethyl acetal], and ethyl 2,3-epoxysuccinaldehydate at their aldehyde groups with ethyl (triphenylphosphoranylidene)acetate, phosphonoacetic acid triethyl ester, (triphenylphosphoranylidene)acetone, (triphenylphosphoranylidene)aeetonitrile, and diethyl (cyanomethyl)phosphonate. The last two reactions lead to the formation of a mixture of cis and trans isomers.This article is published in accordance with a resolution of the Conference of Editors-in-Chief of Journals of the Academy of Sciences of the USSR of July 12, 1962, as a dissertation paper by B. I. Kozyrkin.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 683–688, April, 1966     

生物催化合成光学活性环氧化物

手性环氧化物及其相应的邻二醇在合成上具有重要应用价值。近年来,制取这些手性合成块的合成方法得到了很的大发展。本文着重讨论当前国际上采用生物催化合成光学活性环氧化物的发展状况。     

Ozonides,epoxides, and oxidoannulenes of C(70)

Six new monoadducts of C(70) with oxygen species have been prepared, isolated, and characterized following ozonation of C(70) solutions. The initial products are two ozonide monoadducts, identified as a,b- and c,c-C(70)O(3). These ozonides lose O(2) through thermolysis or photolysis to form various isomers of C(70)O. The a,b-C(70)O(3) isomer dissociates through thermolysis with a decay time of 14 min at 296 K to form the [6,6]-closed epoxide a,b-C(70)O. When photolyzed, it instead forms a [5,6]-open oxidoannulene identified as a,a-C(70)O. These reactions mimic those seen for C(60)O(3). By contrast, the c,c-C(70)O(3) isomer, which has a thermolysis lifetime of 650 min at 296 K, decays thermally only to an oxidoannulene deduced to be d,d-C(70)O. Photolysis of c,c-C(70)O(3) produces a mixture of the oxidoannulenes b,c-C(70)O and c,d-C(70)O plus a minor amount of the c,c-epoxide. All four C(70)O oxidoannulene isomers undergo photoisomerization, giving eventually the a,b- and c,c-C(70)O epoxides.     

Syntheses of perfluorinated epoxides,diepoxides, and a novel rearrangement

t-Butylhydroperoxide/butyl-lithium is a good reagent for synthesis of epoxides and diepoxides from polyfluorinated-alkenes and-polyenes. This reagent and calcium hypochlorite both give a novel diepoxide 5 from perfluoro-3,4-dimethyl-2,4-diene 1; diepoxide 5 undergoes a novel rearrangement, at 200°C, to the corresponding 1,4-dioxine derivative 18. Possible mechanisms are discussed.     

The photochemical preparation of ozonides by electron-transfer photo-oxygenation of epoxides

9,10-Dicyanoanthracene (DCA) sensitizes the electron-transfer photo-oxygenation of epoxides in oxygen-saturated acetonitrile to form ozonides. Epoxides with oxidation potentials lower than 2 V vs SCE quench the fluorescence of DCA and are converted to the ozonides with DCA alone. Epoxides which do not quench the singlet excited state of DCA are unreactive under these conditions. However, the photo-oxygenation of these epoxides can be effected by addition of biphenyl (BP) as a catalyst or co-sensitizer. Investigations of the stereochemistry of the reactions of cis- and trans-2,3-diaryloxiranes has shown that both isomeric epoxides are converted exclusively to the corresponding cis-ozonides. Co-sensitized photo-oxygenation of cis- and trans-2,3-diphenyloxirane affords only cis-3,5-diphenyl-1,2,4-trioxolane. The same stereochemical course is followed for the electron-transfer photo-oxygenation of more easily oxidized 2,3-dinaphthyloxiranes that do not require BP co-sensitization. The stereochemistry of the naphthyl-substituted ozonides has been unequivocably assigned by an X-ray structure of cis-3,5-bis(2'-naphthyl)-1,2,4-trioxolane. The corresponding trans-ozonide was prepared by ozonation of cis-1,2-bis(2'-naphthyl)ethene and stereochemically identified by Chromatographic resolution using high-performance liquid chromatography with optically active (+)-poly(triphenylmethyl methacrylate) as the stationary phase. These stereochemical results have been interpreted in terms of a mechanism involving addition of singlet oxygen as a dipolarophile to intermediate carbonyl ylides.