Catalytic Hydrogenation of α‐Iminophosphonates as a Method for the Synthesis of Racemic and Optically Active α‐Aminophosphonates

Abstract

It was shown that the catalytic hydrogenation of a-iminophosphonates by molecular hydrogen can serve as a convenient method for the synthesis of racemic and optically active a-aminophosphonates. Up to 94% ee was achieved in the rhodiumcatalyzed enantioselective hydrogenation using chiral ligand (R)-BINAP.

Catalytic synthesis and transformations of organophosphorus compounds

“…Of many chiral ligands, it was only (R)-BINAP (R = p-MeC 6 H 4 ) that gave 94% ee (Scheme 29). 66 Catalytic system Pd(OAc F ) 2 -CF 3 CH 2 OH (50 atm, 20°C) was found to be the best in the reduction of α-oxophosphonates, but the use of various chiral ligands, including (R)-BINAP, gave only meager results: α-hydroxyphosphonates were obtained with optical purity up to 41% (Scheme 30).…”

α‐Iminophosphonates: Useful Intermediates for Enantioselective Synthesis of α‐Aminophosphonates

“…Thus, in 2008, Beletskaya and coworkers used Rh‐BINAP ( II ) catalyst to reduce aromatic and heteroaromatic α‐ketiminophosphonates 16 , providing α‐aminophoshonates 17 with yields up to 82% and enantiomeric excesses ranging from 43 to 94% (Scheme ). Unfortunately, this strategy affords low conversion rates below 25% if α‐alkyl ketimines are used …”

An Elegant Microwave Assisted One‐Pot Synthesis of Di(α‐aminophosphonate) Pesticides

“…Recently, this classical reaction has been modified in various aspects, of its reaction conditions such as with or without solvent, presence or absence of catalysts, and the nature of energizing the reactants either conventionally or non‐conventionally. But all these reactions effected under different conditions have several disadvantages like decomposition of the imine intermediate formed during the course of reaction, deactivation of the Lewis acids by water, requirement of high cost moisture sensitive reagents, catalysts, high temperature, long reaction periods, and lower product yields . Further, reported procedures applicability is limited to highly electrophilic carbonyl and strong nucleophilic amine substrates.…”