Methyl isocyanate adds with its CN group to the PN group of 1, 2λ5-azaphospholes and- azaphospholines; depending on the nature of the ring and the phosphorus substituents the bicyclic adducts are stable or redissociate in solution or/and decompose in a Wittig-type reaction.
![2,2-dimethyl-5,5-diphenyl-4,5-dihydro-3H-2λ5-[1,2]azaphosphole-4-carboxylic acid methyl ester Structure](https://image.chemsrc.com/caspic/444/33536-04-8.png)
![methyl 5,5,6-trimethyl-7-oxo-2,2-diphenyl-1,6-diaza-5$l^C21H25N2O3P-phosphabicyclo[3.2.0]heptane-3-carboxylate Structure](https://image.chemsrc.com/caspic/097/68464-31-3.png)