Novel features in the chemistry of (±)-6a,12a-dihydrorotoxen-12(6H)-one, synthetic parent compound of the natural rotenoids

Abstract

Oxidation of the title compound, the parent of the rotenoid group, gives, besides the expected rotoxen-12(6H)-one, a novel dimer whose stereochemistry and conformation have been examined by nuclear magnetic resonance methods. Reduction of rotoxen-12(6H)-one with lithium aluminium hydride yields two novel products, a spiro-compound and a seco-compound: a mechanistic rationalisation is proposed. A self-condensation product derived from the rotoxenone has also been prepared and a structure suggested.

Allylation or prop-2-ynylation of 2,2′-dihydroxydeoxybenzoin occurs at the methylene group to give C-rather than O-substituted products. Treatment of the C-allyl compound with 1 mol. of performic acid causes a free-radical-induced cyclisation in preference to hydroxylation, and gives 2-allyl-2-o-hydroxyphenylbenzofuran. Features of the chemistry of the latter are considered. Hydration of the C-prop-2-ynyl compound with boron trifluoride–red mercuric oxide also effects cyclisation to give a benzofuran.