Small-Ring Compounds. XLII. Synthesis and Reactions of 3-Phenyl-2-cyclobutenone and Some Related Compounds

Abstract

Hydrogenation of either 1,1-difluoro-2,2-dichloro-3-phenylcyclobutane(VII) or 1,1-difluoro-2,2-dichloro-2-phenylcyclobutene (VI) over a palladium-on-charcoal catalyst gave 1,1-difluoro-3-phenylcyclobutane (V). Bromination of V- by N-bromosuccinimide produced 1,1-difluoro-3-bromo-3-phenylcyclobutane(IX) which on dehydrobromination by potassium hydroxide in ethanol afforded 1,1-difluoro-3-phenyl-2-cyclobutene(IV). Hydrolysis of IV by concentrated sulfuric acid gave 3-phenyl-2-cyclobutenone (I). Treatment of I with hot dilute aqueous base produced mixtures of benzoic acid, acetophenone, and benzoylacetone. The ring opening of I in boiling acetic acid gave β-methyl-trans-cinnamic acid. Catalytic hydrogenation of I produced 3-phenylcyclobutanone (XI). Sodium borohydride reduction of I afforded 3-phenyl-2-cyclobutenol (XII) which on catalytic hydrogenation gave cis-3-phenylcyclobutanol (XIII); XIII was also obtained by catalytic hydrogenation of 2-chloro-3-phenyl-2-cyclobutenol( XVI) from the sodium borohydride reduction of 2-chloro-3-phenyl-2-cyclobutenone (XV).

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