Stable arsaalkenes (alkylidenearsanes) 4-6, dihalogenated at the alken
e carbon atom, were synthesized in good yields by a one-pot synthesis
from n-butyllithium, difluoroarsane 1, and, respectively, chloroform,
bromoform, and tetraiodomethane. 4 undergoes nearly quantitative lithi
um-bromine exchange with n-butyllithium at low temperature to give, af
ter quenching with methanol, the monobrominated arsaalkene 10.