ANNULATIONS OF PODOCARPIC ACID-DERIVATIVES VIA AN ARYNE INTERMEDIATE

The cycloaddition of substituted furans to the diterpenoid aryne (39), generated by in situ diazotization of the anthranilic acid (1) follow ed by cleavage of the annulated 1,4-epoxydecahydrochrysenes, provides a convenient method for the preparation in high yield of the previousl y unknown 1-substituted octahydrochrysen-4-ols. Use of 1,3-dipoles und er the same procedure, or under a modified procedure involving pre-iso lation of the diazonium tetrafluoroborate salt (9), gave novel annulat ed heterocyclic products directly. Attempted [2+2] cycloadditions of e lectron-rich alkenes to the diterpenoid aryne (39) were largely unsucc essful but reaction with 1,1-dimethoxyethene by using in situ diazotiz ation gave a product derived from an initial [2+2] cycloaddition.