The regiospecific synthesis of angularly-fused xanthones via the benzannulation of 1,2-adducts derived from 3-(o-anisoyl)-4-substituted cyclobutenediones and their dithianyl derivatives.

Article abstract of DOI:10.1016/S0040-4039(97)00720-X

Described it, this paper is a new synthetic approach to angularlyl-fused and simpler substituted xanthones that is based upon the benzanullation of 2-(o-anisoyl)-4-heteroaryl-2-cyclobutenones and 2-(2-(o-anisyl)-1,3-dithian-2-yl)-4-alkenyl-2- cyclobutenones followed by facile intramolecular loss of methanol and cyclization to the xanthone.