- α-Chloroalkylmagnesium reagents of >90% ee by sulfoxide/magnesium exchange
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Not only for ligand exchange at sulfoxides can the sulfoxide/magnesium exchange reaction be used, but it also provides a possibility to generate Grignard reagents in way that avoids metallic magnesium and thus radical processes. Therefore, enantiomerically pure Grignard reagents can be obtained from the corresponding sulfoxides [Eq. (a)].
- Hoffmann, Reinhard W.,Nell, Peter G.
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p. 338 - 340
(2007/10/03)
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- Process for the preparation of an oxirane, azirdine or cyclopropane
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A process for the preparation of an oxirane, aziridine or cyclopropane of formula (I) wherein, X is oxygen, NR4 or CHR5 ; R1 is hydrogen, alkyl, aryl, heteroaromatic, heterocyclic or cycloalkyl; R2 is hydrogen, alkyl, aryl, heteroaromatic, CO2 R8, CHR14 NHR13, heterocyclic or cycloalkyl; or R1 and R2 join together to form a cycloalkyl ring; R3 is hydrogen, alkyl, aryl, heteroaromatic, CO2 R8, R83 Sn, CONR8 R9 or trimethylsilyl; R4 and R5 are, independently, alkyl, cycloalkyl, aryl, heteroaromatic, SO2 R8, SO3 R8, COR8, CO2 R8, CONR8 R9 or CN, or R4 can also be P(O)(aryl)2 ; R8 and R9 are independently alkyl, aryl or arylalkyl; R13 and R14 are independently hydrogen, alkyl or aryl; the process comprising reacting a mixture of a compound of formula (II), wherein R1, R2 and X are as defined above, and a sulphide of formula SR6 R7, wherein R6 and R7 are independently alkyl, aryl or heteroaomatic, or R6 and R7 join together to form a cycloalkyl ring which optionally includes an additional heteroatom, with either (i) a metallocarbon obtainable by reacting an alkylmetal with a methane derivative of formula CHR3 X'X", wherein R3 is as defined above, and X' and X" are independently, a leaving group, or (ii) a metallocarbon obtainable by reacting a compound of formula (III), (wherein R3 may not be hydrogen) with a suitable organometallic or inorganic reagent.
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- A NOVEL SYNTHESIS OF EPOXIDES AND ALLYLIC ALCOHOLS FROM CARBONYL COMPOUNDS THROUGH α,β-EPOXY SULFOXIDES
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Treatment of α,β-epoxy sulfoxides, easily prepared from carbonyl compounds with 1 equivalent of n-butyllithium at -100 deg C gave the desulfinated epoxides in good yields.The similar α,β-epoxy sulfoxides having arylmethyl group at α-position, on treatment
- Satoh, Tsuyoshi,Kaneko, Youhei,Yamakawa, Koji
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p. 2379 - 2382
(2007/10/02)
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- Oxyanionic Substituent Effect on the C-H Insertion of Carbenes. Reaction of Alkoxides with Dichlorocarbene and Chlorophenylcarbene
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The lithium alkoxides of benzylic, allylic, and simple alkyl alcohols were allowed to react with chloroform in the presence of t-BuOLi in THF-hexane to give, in 32-91percent yields, dichloromethylcarbinols, which were produced by the insertion of dichlorocarbene into the α C-H bond of alkoxides but not by the Wittig rearrangement of carbanions of alkyl dichloromethyl ethers.The enhanced reactivity toward dichlorocarbene of the α C-H bond of alkoxides was clearly demonstrated by the high selectivity of the insertion.The potassium alkoxides of a series of analogous alcohols reacted analogously with benzal chloride in the presence of t-BuOK in THF to give the corresponding substituted oxiranes (16-79percent); e.g., the reaction of potassium benzyl oxide gave 2,3-diphenyloxirane (79percent) as a mixture of stereoisomers (trans:cis = 1.0).With 2-phenethoxide, n-octyl oxide, or 2-methoxyethoxide, the corresponding dialkyl acetals of benzaldehyde were also formed in 9, 6, and 6percent yield, respectively, and their formation is explained in terms of nucleophilic attack of alkoxide on chlorophenylcarbene.With trans-crotyl oxide or 2-phenetoxide, 1,3-diphenylpropan-1-one(33percent) and 1-phenylpent-3-en-1-one (6percent) were produced, respectively, as byproducts through the isomerization of the primary product oxiranes.Oxiranes were produced by the insertion of chlorophenylcarbene into the α C-H bond of alkoxides followed by the cyclization of the intermediate 1-substituted 2-chloro-2-phenethyl alkoxide.These reactions provide us with new preparative methods of synthetically useful dichloromethyl carbinols and oxiranes.
- Harada, Toshiro,Akiba, Eiji,Oku, Akira
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p. 2771 - 2776
(2007/10/02)
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