Diastereoselective Lewis acid mediated hydrophosphonylation of heterocyclic imines: a stereoselective approach towards alpha-amino phosphonates

The synthesis of new chiral a-amino phosphonates by the Lewis acid mediated addition or bisesters or phosphonic acid to 3-thiazolines (2,5-dihydro-1,3 -thiazoles), is described. The diastereoselectivity of the reaction using c hiral reactants was systematically investigated. The chiral BINOL-phosphona te 1 was found to be a highly stereoselective phosphonylating agent towards 3-thiazolines. Structural aspects of the resulting thiazolidinylphosphonat es were studied by NMR and X-ray analyses. The role of the Lewis acid as a spatial mediator is discussed and a quantum chemical description of the Lew is acid mediated hydrophosphonylation presented.