Cyclic oxyphosphoranes in synthesis. A novel synthesis of oxathiaphospholenes, fused pyrimidines, and aminooxyphosphoranes

Trialkyl phosphites induced the condensation of one molecule of 3,5-di-tert-butyl-1,2-benzoquinone (1) with two molecules of methyl-, ethyl-, phenyl- and hexyl iso thiocyanates (6a-6d) leading to the formation of quinazoline-2,4-dithione derivatives (12a, 12b, 14, and 15) and trialkyl phosphates. Three steps were involved, and the intermediates could, but need not, be isolated. In the second step, the intermediates, new six-membered phosphorus heterocycles 8a-8d were isolated and identified. In contrast, condensation of 4,6-di-tert-butylbenzo-2-methoxy-2oxo-1,3,2-dioxaphosphole (19) with one molecule of 6a-6d afforded the corresponding aminooxyphosphoranes 22a-22d. Allyl iso thiocyanate (16), on the other hand, reacted with 2,2,2-trialkoxy-1,3,2-dioxaphospholenes 3a and 3b to give the phosphates 18a and 18b whereas with 19 spirocyclic oxaphosphole 24 was isolated.