ChemInform Abstract: Synthesis of Spiro[2.6]nonadienones and Spiro[3.6]decadienones by the Reaction of Cyclopropyl‐ and Cyclobutylmagnesium Carbenoids with Lithium Phenolates and Naphtholates.

Abstract

Treatment of 1-chlorocyclopropyl p -tolyl sulfoxides and 1-chlorocyclobutyl p -tolyl sulfoxides with a Grignard reagent at low temperature afforded cyclopropylmagnesium carbenoids and cyclobutylmagnesium carbenoids, respectively, via a sulfoxide–magnesium exchange reaction. The reaction of these magnesium carbenoids with lithium phenolates afforded spiro[2.6]nona-6,8-dien-5-ones and spiro[3.6]deca-7,9-dien-6-ones, respectively; however, the yields were rather low. Reaction of the cyclopropylmagnesium carbenoids with lithium 1-naphtholates gave spiro[2.6]nona-5,7-dien-4-ones in moderate to good yields; however, reaction of the cyclobutylmagnesium carbenoids with lithium 1-naphtholates did not give the desired products. Reaction of the cyclopropyl- and cyclobutylmagnesium carbenoids with lithium 2-naphtholates gave spiro[2.6]nona-5,7-dien-4-ones and spiro[3.6]deca-7,9-dien-6-ones, respectively, in moderate to good yields. These unprecedented reactions provide a procedure for the synthesis of spiro[2.6]nona-5,7-dien-4-ones and spiro[3.6]deca-7,9-dien-6-ones from 1-naphthols and 2-naphthols with a one-carbon ring expansion of the phenol ring.