Bisphosphinite

Table 27.5 Enantiomeric hydrogenation using bisphosphinite, bisphosphonite, or bisphosphite. 

Table 27.6 Enantiomeric hydrogenation of tetrasubstituted substrates using bisphosphinite ligands. 

The enantioselectivities were found to be relatively independent of the solvent used. In 1998, Zhang reported a bisphosphinite based on a rigid bis-cyclopentyl ring system (BICPO, 95, 96) which induced 45.7 to 95% ee in the hydrogenation of a-dehydroamino acid derivatives [85]. 

The Schlenk tube was filled with bisphosphinite ligand, (1R, 3R, 5R, 6S)-3,6-bis [bis (4 -fluorophenyl) phosphinooxy] bicyclo[3.2.0]heptane (6.7 mg), degassed methanol (3 mL) and (COD)2Rh 1 BF4 (5.25 mg). The reaction mixture was stirred at room temperature until all the material was dissolved (10 15 minutes) giving an orange solution. 

---