α-Phosphino Amino Acids: Synthesis, Structure, and Reactivity of Phosphaprolines

Abstract Linear phosphinoglycines proved sensitive to hydrolysis. Routes to heterocyclic α-phosphino amino acids were therefore investigated. The more stable phenylphosphaproline and some N- or C2-substituted derivatives thereof were synthesized from 2-phenylphosphino-ethylamines and α-ketocarboxylic acids. With Ni(COD)2 they form greenish yellow complex solutions that in the presence of NaH generate ethylene oligomerization catalysts.