HOMOCHIRAL KETALS IN ORGANIC SYNTHESIS. DIASTEREOSELECTIVE CYCLOPROPANATION OF α,β-UNSATURATED KETALS DERIVED FROM 1,4-Di-O-BENZYL-L-THREITOL

Article abstract of DOI:10.1016/S0040-4020(01)90002-X

2-Cykloalken-1-one 1,4-di-O-benzyl-L-threitol ketals undergo efficient and diastereoselective cyclopropanation when treated with an excess of the Simmons-Smith reagent.For example, 2-cyclohexen-1-one 1,4-di-O-benzyl-L-threitol ketal gave in 90-98percent yield a 9:1 mixture of diastereomeric cyclopropanes as established by 62.9 MHz ¹³C NMR spectroscopy and by hydrolysis of the mixture to (1R,6S)-bicyclo<4.1.0>heptan-2-one.Sixteen other examples are presented which demonstrate the generality and predictability of the process for 2-cycloalken-1-one ketals, as well as an unfortunate lack of diastereoselectivity for α,β-unsaturated 1,4-di-O-benzyl-L-threitol acetals.