Abstract: 13C NMR studies on the title compounds have succeeded in freezing out rotation around the exocyclic P-NR2 bond at low temperatures. The preferred conformation has one NR group syn to the phosphorus lone pair, and the other lies across the face of the diazaphospholane ring. The barriers to rotation around the exocyclic PN bond are 8.1 and 10.1 kcal mol-'for R= CH2CH3 and CH (CH3) 2, respectively.'Jpy (exo) is much larger than ...
