sustainable and environmentally benign alternative to hazardous insecticides. 4-Methylheptan-3-ol is an interesting example of an insect pheromone, because its stereoisomers are active towards different species. All four possible stereoisomers of this compound were prepared from 4-methylhept-4-en-3-one by a one-pot procedure in which the two stereogenic centres were created during two sequential reductions
significantly by the steric effect of bulky groups. However, the influence of steric alkylchain length has not been studied for the diastereoselectivity. In this work, we present a new strategy for the racemic synthesis of β-methyl alcohols to obtain various diastereomer ratios using the Felkin–Anh model. The addition of alkyl Grignard reagents to α-methyl aldehydes afforded diastereomer ratios of threo/erythro
an efficient catalytic system for the enantioselectiveaddition of alkyl Grignard reagents to a broad range of aliphatic aldehydes with good yields and enantioselectivities. Remarkably, the challenging methylmagnesium bromide (MeMgBr) can also be added to a variety of aliphatic aldehydes, providing versatile chiral methyl carbinol units with unprecedented yields and enantioselectivities in a simple
[2,3]-Wittig sigmatropic rearrangement of crotyl propargyl ether system. An emerging tool for control of acyclic stereochemistry
作者:Kōichi Mikami、Ken-Ichi Azuma、Takeshi Nakai
DOI:10.1016/0040-4020(84)80013-7
日期:1984.1
The [2,3]-Wittigrearrangement of properly designated (E)- and (Z)-crotyl propargylether system has been shown to exhibit a remarkably high degree of threo- and erythro -selection, respectively, and the stereochemical outcomes are discussed on mechanistic grounds. Some useful transformations of the rearrangement product are also described within the context of the formal total synthesis of (±)-oudemansin
starting from 4-thianones. Key steps in the synthesis include: (a) reduction of 3-propyl-4-thianone to yield an easily separable isomeric mixture of cis- and trans-3-propyl-4-thianols; and (b) a highly efficient resolution of the particular cis/trans-isomers through a chromatographic separation of their respective esters with (S)-chlorofluoroacetic acid. Subsequent hydrolysis and desulfurization gave