P-Stereogenic AMPP Ligands

After ring opening of 7 by an organolithium, the opened aminophosphine alkoxide 12 can be trapped with an equivalent of a chlorophosphine to afford 66 after boronation. Alternatively, attack of 12 on a highly enantioen-riched chlorophosphine borane 31 affords the doubly P-stereogenic compounds 67. Both 66 and 67 can be easily deprotected with DABCO in toluene, for example, with complete retention of configuration at the phosphorus atom. 

Although prepared differently, all these ligands can be formally considered as derivatives of the non P-stereogenic EPHOS ligand (R = = Ph) (Table 4.6). 

A variety of substituents have been introduced in good yields with high stereoselectivity ( 92% de), proving the versatility of the synthetic scheme. It has to be kept in mind that the absolute configuration of each of the stereogenic centres of the molecules 67 and 68 can be individually selected simply by changing the ephedrine enantiomer used in the preparation of 7 and/or 31. This 

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Aminophosphine phosphinite (AMPP) ligands constitute an important class of non-C2 diphosphorus ligands. Some of them are prepared from ephedrine and therefore the Juge-Stephan method constitutes an ideal procedure for the synthesis of P-stereogenic AMPP ligands (Scheme 4.30). ... 

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