Photoinduced molecular transformations. Part 156. New photoadditions of 2-hydroxy-1,4-naphthoquinones with naphthols and their derivatives

Article abstract of DOI:10.1016/0040-4020(94)01026-V

Dinaphtho[2,1-b;1',2'-d]furan-12,13-diones are produced in one-step in up to 45% yield by a (3+2) photoaddition of 2-hydroxy-1,4-naphthoquinones with 2-naphthol, while (±)-(6aα,6bβ),12aβ,12bα)-6a,6b,12a,12b-tetrahydro-12b-hydroxydina phtho-[1,2-a;1',2'-c]cyclobutenes (14-16%), arising from stereoselective addition of a (2+2) photoaddition, are products in the photoaddition of 2-hydroxy-1,4-naphthoquinone with 2-methoxynaphthalene and with 2-naphthyl acetate. The photoaddition of 2-hydroxy-1,4-naphthoquinone with 2-methoxynaphthalene also gave 2-hydroxy-3-(2-methoxynaphth-1-yl)-1,4-naphthoquinone (23%) as an accompanying product. Similar irradiation of a solution of 2-hydroxy-1,4-naphthoquinone with 1-methoxynaphthalene in acetone gave cis-6a,13a-dihydro-13a-methoxydinaphtho[1,2-b;2',3'-d]furan-7,12-dione arising from a (3+2) photoaddition in 24% yield. The probable mechanisms for the formation of the photoadducts are discussed.