A Novel Configuration-Controlled Stereoselectivity in Enol Silylation of Ketones. Stereochemistry of Amine-Promoted Enol Silylation of Meso and Racemic α,α′-Dichloro Ketones and of Ketonization of the Resultant Enol Silyl Ethers
Stereochemistry in amine-promoted enol trimethylsilylation of meso- and dl-α,α′-dichloro ketones, RCHClCOCHClR (1a; R = Me and 1b; R = i-Pr), and in ketonization of the resultant enol silyl ethers (2a and 2b) has been studied. The Et3N-promoted silylation of 1 in benzene shows a marked diastereoselectivity; the racemic isomer exhibits 84% and 98% (E)-selectivities for 1a and 1b, while the meso isomer
Cleavage of the oxygen bridge in 8-oxabicyclo[3.2.1]octanes by reductive elimination
作者:Baldur Föhlisch、Günter Kreiselmeier
DOI:10.1016/s0040-4020(01)01051-1
日期:2001.12
Several 2(4)-bromo- or chloro-8-oxabicyclo[3.2.1]oct-6-en-3-ones (2), available by [4+3] cycloaddition of monohalogeno-oxyallyl intermediates with furans, were reduced to halogenated 8-oxabicyclo[3.2.1]oct-6-en-3endo-ols (6) and saturated analogues (7). Cycloheptene-1,3trans-diols (8,11) were formed preferentially by reductive elimination.