Stereoselective addition of dialkyl phosphites to di-salicylaldimines bearing the (R,R)-1,2-diaminocyclohexane moiety

The addition of dialkyl phosphites to the azomethine bond of N,N′-disalicylidene-1,2-diaminocyclohexane imines, catalyzed by sodium hydride led to bis-aminophosphonates in a high diastereoselectivity. One of the bis-aminophosphonates was analyzed by X-ray diffraction. Another bis-aminophosphonate was converted to a bis-aminophosphonic acid and the structure was studied by X-ray diffraction. Addition of phosphites to a diimine resulted in an aminophosphonate, which was also studied by X-ray diffraction. An explanation of the diastereoselectivity is suggested.