Chemically efficient aza-di-π-methane photoreactivity with novel stable derivatives of β,γ-unsaturated carbonyl compounds

Abstract

The syntheses of new stable derivatives of β,γ-unsaturated carbonyl compounds such as 2,2-dimethyl-4,4-diphenylbut-3-enal 6 and 3,3-dimethyl-5,5-diphenylpent-4-en-2-one 7 are described. The majority of these derivatives undergo efficient aza-di-π-methane rearrangement on short, acetophenonesensitized, irradiation to afford the corresponding derivatives of the cyclopropane carbonyl compound in good to excellent yield; for example, the photoconversion of the oximino trifluoro acetate of the aldehyde 6 affords 2,2-dimethyl-3,3-diphenylcyclopropane-1-carbonitrile 16 in 80% yield. This is of synthetic value since β,γ-unsaturated nitriles do not undergo the aza-di-π-methane reaction. The study has also indicated some limits to the type of derivative that can be used. Thus with a methyl ketone derivative where the functional group can undergo SET from the triplet 1,1-diphenylvinyl moiety; an alternative fragmentation path can be operative in a novel reaction not seen previously in such systems.