Photoinduced molecular transformations. 140. New one-step general synthesis of naphtho[2,3-b]furan-4,9-diones and their 2,3-dihydro derivatives by the regioselective [3 + 2] photoaddition of 2-hydroxy-1,4-naphthoquinones with various alkynes and alkenes: application of the photoaddition to a two-step synthesis of maturinone
作者:Kazuhiro Kobayashi、Hideki Shimizu、Akiyoshi Sasaki、Hiroshi Suginome
DOI:10.1021/jo00069a023
日期:1993.8
2,3-Dihydronaphtho[2,3-b]furan-4,9-diones can now be produced in one step in 41-83% yields by an unprecedented regioselective [3 + 2] photoaddition of 2-hydroxy-1,4-naphthoquinones with a variety of alkenes. The dihydronaphthofurandiones can be readily transformed into naphtho[2,3-b]furan-4,9-diones. This new photoaddition reaction has been successfully applied to a two-step synthesis of maturinone, a constituent of Cacalia decomposita A Gray. Naphtho[2,3-b]furan-4,9-diones can also be obtained directly by a new [3 + 2] photoaddition of 2-hydroxy-1,4-naphthoquinone with various alkynes in acetone. The photoaddition between 2-hydroxy-1,4-naphthoquinones and alkenes in acetone involves an initial formation of furanohydroquinones, which are oxidized to furanoquinones. A quenching experiment together with the regioselective nature of photoaddition indicate that the photoaddition is a two-step process from a triplet of excited quinones and involves more stabilized polar biradicals or ionic intermediates generated from them by an intramolecular electron transfer from which the furanohydroquinones are formed.