Some unexpected products from the treatment of organoboranes from α,β-unsaturated ketones with acetic acid–acetic anhydride

Abstract

The synthesis of 1β-acetoxy-9β-methyl-Δ⁵-trans-octalin from 9-methyl-Δ⁵⁽¹⁰⁾-octalin-1,6-dione has been carried out by treatment of the dione with a large excess of lithium aluminium hydride in ether and then boron trifluoride etherate followed by heating the resulting organoboranes with acetic acid–acetic anhydride. The yield was low (16%). Unexpectedly, a small yield of 1α,2β,5β-triacetoxy-10β-methyl-trans-decalin was obtained although no specific oxidising agent was used. Under similar conditions 10-methyl-Δ¹⁽⁹⁾-octalin-2-one and cholest-4-en-3-one also afforded oxidation products, viz. 1α,2β-diacetoxy-10β-methyl-trans-decalin (26% yield) and 3β,4α-diacetoxy-5α-cholestane (19% yield). No evidence has yet been obtained concerning the mechanism whereby the organoboranes are oxidised.