Intramolecular keto-carbenoid addition to double bonds: stereochemistry of the catalytic reduction of Δ9(11)-gibbenes and related compounds

Abstract

Decomposition of some γδ-unsaturated α-diazomethyl ketones using an ‘activated CuO catalyst’ under irradiation with a tangsten lamp results in a significant increase in the yields of the corresponding intramolecular keto-carbenoid addition products; the substituents effect in controlling the stereoselectivity in the catalytic hydrogenation of a few pentacyclic ketones and Δ⁹⁽¹¹⁾-gibbene derivatives have been evaluated, leading to stereocontrolled syntheses of some C-9 epimeric gibbane synthons and a degradation product of gibberellin A₁₃.