Phosphinoglycines - Synthesis, Structure, and Reactivity

The one-pot three-component reaction of a secondary phosphine and a primary amine with glyoxylic acid hydrate in diethyl ether leads via phosphonium-bis(glycolates)(1) to organoammonium phosphinoglycolates or to phosphinoglycines or a mixture thereof. The amino-substituted phosphinoacetic acids may, like diphenylphosphinoacetic acid itself, form ethylene oligomerization catalysts with Ni(COD)(2). (2)The investigations presented here unveil that this as well as the preference for reactions giving hydroxy- or amino-phosphinoacetic acids depends on the size of the substituents and the basicity of the amine. The behavior of small and bulky substituted primary alkyl amines (iPr, nPr, tBu, 1-Ada) and less N-basic aryl (C6H3-2,4-COOMe)(2)) and heteroaryl amines in the three-component reactions, the catalytic screening, and the crystal structures of the smallest isolated N-substituted diphenylphosphinoglycines so far, (R = iPr -see Figure 1, nPr) are shown.