Aminophosphinic Acids in a Pyridine Series: Cleavage of Pyridine-2- and Pyridine-4-methyl(amino)phosphinic Acids in Acidic Solutions

The synthesis of a series of new pyridine aminomethylphosphinic acids is described. These compounds were obtained in the reaction of the corresponding pyridine aldehydes with primary amines and with ethyl phenylphosphinate, or methylphosphinate, in the presence of bromotrimethylsilane. In aqueous, strong acid solutions, pyridine aminophosphinic acids were split, forming the phenyl-, or methylphosphonic, acid and the corresponding secondary pyridyl-alkylamines. The kinetics of some observed cleavages were measured, and a mechanism of the cleavage has been proposed.

keywords:

• Aminophosphinic acids
• bromotrimethylsilane
• cleavage reactions
• phosphonic acids
• pyridine aminophosphinic acids
• pyridyl amines

Acknowledgments

The authors are thankful to the Faculty of Chemistry, Wroclaw University of Technology, Wroclaw, Poland.

Notes

^a Kinetic data for 1M H₂SO₄ solutions.

^b Kinetics measured in 50% aqueous methanol.