A One-Pot Procedure for the Synthesis of α-Amino Phosphonates from Alkynes

A new and highly flexible procedure for the synthesis of α,α-disubstituted α-amino phosphonates is described with disubstituted alkynes, primary amines and diethyl or dimethyl phosphite as starting materials. The reaction sequence, which is performed as a one-pot operation, starts with a Cp2TiMe2-catalyzed hydroamination of the alkyne. A subsequent nucleophilic addition of diethyl or dimethyl phosphite to the resulting imine, performed in the presence of catalytic amounts of Me2AlCl, gives the desired α-amino phosphonate. The application of intermolecular and intramolecular hydroamination reactions leads to the formation of both, cyclic and acyclic α-amino phosphonates.