Synthesis of 2a,8b-Dihydrocyclobuta[a]naphthalene-3,4-diones

Abstract

On irradiation (λ = 350 nm) in neat hex-1-yne, naphthalene-1,2-dione monoacetals 1 afford mixtures of pentacyclic photodimers and up to 25% (isolated yield) of mixed photocycloadducts 2. Careful acidic hydrolysis of the acetal function of 2 gives the title compounds 3, the overall sequence representing a first approach to a (formal) [2 + 2] photocycloadduct of a 1,2-naphthoquinone to an alkyne.

Keywords

• cyclobutenes
• photocycloaddition
• quinone monoacetals