Synthesis and resolution of diastereomers of (R,R)-1,2-cyclohexylenediamino-di-phenylmethylphosphonates

Abstract

Salen-like compounds, such as bis-aminophosphonic systems bearing a (R,R)-1,2-diamino-cyclohexyl (DACH) moiety, were synthesized by the addition of dialkyl phosphites to the azomethine bond of N,N′-dibenzylidene-1,2-diaminocyclohexane 2. Five bis-aminophosphonates, dimethyl, diethyl, diisopropyl, dibenzyl, and diallyl derivatives, were obtained in high diastereoselectivity. Three of these compounds, dimethyl 3a, diethyl 3b, and diisopropyl 3c derivatives, had the predominant diastereoisomers separated. A hypothetical explanation of the diastereoselectivity is also reported.