Reactions of Arylenedioxytrihalophosphoranes with Acetylenes: XV.1 Reaction of 2,2,2-Tribromo-4,6-di-tert-butylbenzo-1,3,2λ5-dioxaphospholedioxaphosphole with Pent-1-yne

2,2,2-Tribromo-4,6-di-tert-butylbenzo-1,3,2λ5-dioxaphospholedioxaphosphole reacted with a terminal alkyne, pent-1-yne, to give a mixture of two isomeric 1,2-benzoxaphosphinine derivatives, 6,8- and 5,7-di-tert-butyl-2-bromo-4-propylbenzo-1,2λ5-oxaphosphinin-2-oxides, at a ratio of 5.9: 1. The regioselectivity of substitution of oxygen in the dioxaphosphole fragment by carbon differs from that observed previously in the reaction with 4,6-di-tert-butyl-2,2,2-trichlorobenzo-1,3,2λ5-dioxaphosphole: the minor isomer was formed as a result of substitution of the oxygen atom in the ortho position with respect to one tert-butyl group of the initial phosphole.