Solid-phase synthesis of novel 7,8-functionalized pyrazolo[1,5-a][1,3,5]-2-oxo-4-thioxotriazine derivatives via cyclization reactions of dithiocarboxy resin bound pyrazoles.

A general method is described for the solid-phase synthesis of novel 7,8-functionalized pyrazolo[1,5-a][1,3,5]-2-oxo-4-thioxotriazine derivatives. The sequence developed for this purpose is based on cyclization reactions of resin-bound 3,4-functionalized-5-amino-1-dithiocarboxypyrazoles 4 and 5, promoted by reaction with various isocyanates. The resin-bound pyrazoles produced by cyclization reactions of cyanocarboimidates 8 or 3-ethoxyacrylonitriles 9 with Merrifield resin linked hydrazine dithiocarbazate 3, serve as key intermediates for subsequent bicyclic heterocycle diversification. Reactions of the resin-bound 5-amino-1-dithiocarboxy pyrazoles 4 and 5 with various aryl isocyanates produce the novel 7,8-functionalized pyrazolo[1,5-a][1,3,5]-2-oxo-4-thioxotriazine derivatives 6 and 7 in good yields and high purities.