Some Transformations of Adducts of 3,6-Dimethoxy-4,5-methylenedioxy-1,2-didehydrobenzene and Furans. An Approach to the 5,8-Dimethoxy-6,7-methylenedioxynaphtho[2,3-c]furan-4,9-dione Ring System of Ventilone A

Abstract

Adducts derived from the aryne 3,6-dimethoxy-4,5-methylenedioxy-1,2-didehydrobenzene (19) with furan and 2-methoxyfuran have been converted into 5,8-dimethoxy-6,7-methylenedioxy-1,2-naphthoquinone (22) and 5,8-dimethoxy-6,7-methylenedioxy-1,4-naphthoquinone (24) respectively. The trapping of (19) with 1H,3H-furo[3,4-c]furan (38) yielded an unstable adduct (37), which on acid-catalysed ring opening and subsequent oxidation was transformed into 5,8-dimethoxy-6,7-methylenedioxynaphtho[2,3-c]furan-4,9-dione (36), a compound possessing the ring system of the naturally occurring quinone ventilone A.