STEREOSELECTIVE SYNTHESIS OF SOME CIS 2,3-DISUBSTITUTED CYCLANONES RING SIZE INFLUENCE ON THE STEREOSELECTIVITY OF 2-SUBSTITUTED ENDOCYCLIC ENOLATES PROTONATION

Article abstract of DOI:10.1016/S0040-4020(01)96751-1

Conjugate addition of carbanionic reagents formed from aryl- or phenyl-thioacetonitriles 1a-c and 2 to 2-methyl and 2-phenyl 2-cyclohexenone or 2-methyl 2-cyclopentenone, followed by acidic quench, under kinetic control, leads to different ratios of cis and trans 2,3-disubstituted cyclanones according to ring size.From 2-methyl and 2-phenyl 2-cyclohexenone, the cis isomer is highly predominant (85 to 98percent).From 2-methyl 2-cyclopentanone a cis/trans mixture is obtained: the cis isomer only predominates when a bulky reagent (1c) is used (80percent); in the other cases a mixture of nearly 1:1 is obtained.