1-Mesityl 2, 3-dimethylphosphirene 1 and 1-mesityl 2-methylphosphirene 4 can be easily prepared from mesityldichlorophosphine (MesPCl2), AlCl3, 2-butyne or propyne and Bu3P. Because of the steric bulk of the mesityl substituent, n-butyllithium no longer reacts by nucleophilic addition onto the phosphorus atom of the phosphirene ring but instead, as a base, deprotonates the ring substituents. With 1, an allenylphosphine anion results after ...
