Annulation Reactions Leading to Naphtalene Derivatives. New Syntheses of Natural 1,2- and 1,4-Naphthoquinones

Article abstract of DOI:10.1021/jo00218a022

1-(Phenylsulfonyl)-2-oxo-3-(methoxycarbonyl)-1,2,3,4-tetrahydronaphthalene derivatives with various C-3 substituents were effectively prepared by a one-step cyclization involving 1-<(phenylsulfonyl)methyl>-2-(bromomethyl)benzene derivatives and monosubstituted malonic esters.A high yield one-step decarboxylation-desulfonylation of the above products by lithium iodide led to C-3-substituted 2-naphthalenols 7a-g whereas prior C-1 alkylation of the cyclization products provided 1,3-dialkylated 2-naphthalenols 6s,b.Oxidations of compounds 7 to o-naphthoquinones 8a-f further oxidations of the above products to substituted 2-hydroxy-1,4-naphthoquinones provided a new pathway to naturally occuring naphthoquinones like phthiocol (9), droserone methyl ether (10), and lapachol (15).