T. Wegmann et al., ORGANOPHOSPHORUS COMPOUNDS .73. THE TRI-T ERT-BUTYL-2-CYCLOPROPEN-1-YL SUBSTITUENT AS KINETICALLY STABILIZING GROUP FOR 1-AZA-3-PHOSPHAALLENES, Chemische Berichte, 126(11), 1993, pp. 2525-2530
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.