ORGANOPHOSPHORUS COMPOUNDS .73. THE TRI-T ERT-BUTYL-2-CYCLOPROPEN-1-YL SUBSTITUENT AS KINETICALLY STABILIZING GROUP FOR 1-AZA-3-PHOSPHAALLENES

The cyclopropenylphosphane 5 reacts with the isocyanates 6a-g to form the phosphaalkenes 7a-g. An analogous transformation occurs with the s ame phosphane and the bifunctional isocyanates 8a, b (--> 9a, b). In c ontrast, the reaction 5 + 6h ends at the stage of the tautomers 11h re versible 12h. Methanolysis of 7b and of 11h reversible 12h leads to th e carbamoyl-cyclopropenylphosphanes 14a and b, respectively. Sodium hy droxide-catalyzed elimination of hexamethyldisiloxane from 7b, g and t he tautomer mixture 11h reversible 12h yields the target 1-aza-3-phosp haallenes 16a-c.