ORGANOTIN AND -MERCURY ROUTES TO ENONES, DIENONES AND SPIROACETALS

Article abstract of DOI:10.1016/0040-4020(89)80026-2

Conjugate addition of trimethyltinlithium to cyclohex-2-enone followed by enolate trapping with alkylating agents provide trans-2-alkyl-3-trimethylstannylcyclohexanones, which on reaction with Grignard reagents derived from 4-bromo-1-butene or 5-bromo-1-pentene afford tertiary γ-stannylcyclohexanols in a highly diastereoselective fashion.Trimethylstannyl-triggered ring fragmentation (by lead tetraacetate in benzene) leads efficiently to 1,6-dioxaspiro<4.5>decanes and 1,7-dioxaspiro<5.5>undecanes, some of which are of insect origin.Epoxidation of these dienones, followed by acid catalysed hydrolysis and cyclisation leads to hydroxy substituted spiroacetals.Syntheses of 6-oxononan-1-ol (a glandular component of the fruit flies, D. halfordiae and D. occipitalis) and E-6-oxononan-2-one, which is transformed readily into exo or endo-brevicomin, are also presented.Some dialkyl substituted <4.5>- and <5.5> spiroacetals have been acquired also by free radical addition reactions etc., utilising organomercury chemistry.