Stereocontrolled Asymmetric Synthesis of Optically Active Acylcyclopropane Derivatives by Michael Additions of Bromomalonate to Chiral .ALPHA.-Acylvinylic Sulfoxides.
作者:Kunio HIROI、Yoshihisa ARINAGA
DOI:10.1248/cpb.42.985
日期:——
Michael addition of bromomalonate carbanions to chiral α-acylvinylic sulfoxides and the subsequent intramoleculer alkylation yielded optically active acylcyclopropane derivatives with high enantiomeric excess. Stereochemistry of the product was determined by chemical correlation to a compound of known absolute configuration. The mechanism for the asymmetric induction is deduced on the basis of the stereochemical results obtained.
A novel chiral intermediate, 2-ethoxyethyl p-tolyl sulfoxide (4), permits access in one step to optically active α-methylene-β-oxo sulfoxides, which are very useful dienophiles.
Heterocycloaddition of optically active (S)-(+)-3-p-tolylsulfinylbut-3-en-2-one 1 was successfully achieved with various electron-rich dienophiles in extremely mild and non-catalytic conditions. Nature of the dienophile (enol ether 2 v.s. styrene 3) proved to play a critical role in the stereochemical outcome of the reaction: less than 14% de with 2, more than 94% de with 3.
The reaction of (S,E)-3-(p-tolylsulfinyl)pent-3-en-2-one with an isopropyl radical, generated from isopropyl iodide and triethylborane, gives the non-stereoselective addition product and an unexpected α-(arylsulfanyl) enone which is formed through a radical addition and subsequent Pummerer-type rearrangement. The formation of the α-(arylsulfanyl) enone depends upon the additives used as well as the aryl group on the sulfur.