Aryl- and heteroaryl-dichlorophosphines
are mildly and selectively
made in a one-pot synthesis in moderate to good yields starting from
the respective aryl bromides or five-membered heterocycles, following
lithiation with nBuLi, transmetalation with ZnCl2, and subsequently the reaction with PCl3. Selected
aryl- and heteroaryl-dichlorophosphines were successfully synthesized
using this reaction method and could easily be purified after isolation.
The intermediate formation of the organozinc species is essential,
as it prevents the formation of multiple substitution products. Important
are also the reaction conditions: the usage of the proper solvent
for the respective aromatic precursors and removal of the remaining
salts by addition of a dioxane/pentane mixture. Depending on the solvent
and steric demand of the substituent, mono- and bis-substitution products
can be formed but formation also prevented. Hereby, different organozinc
species might play an important role.