Bisphosphinite ligand

Table 27.6 Enantiomeric hydrogenation of tetrasubstituted substrates using bisphosphinite ligands. 

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. 

A unique preference was found using the nonsynunetric P,N system for C-C activation without detecting the normally competing C-H activation process [Eq. (6.122)]. As shown earlier [see Eqs. (6.73) and (6.74)],fine-tuning the structure of complexes allowed selective intramolecular C-H or C-C activations." Exclusive C-C activation could also be achieved with a bisphosphinite ligand. "... 

Despite high volumes of aldehyde products that are manufactured and a deep understanding of the catalytic mechanistic process, no successful industrial asymmetric hydroformylation process has been achieved. Rhodium and platinum catalysts that contain chiral bisphosphine and bisphosphinite ligands have provided the highest enantioselectivies in the study of asymmetric hydroformylation and are chronicled in several reviews [10.92-94]. 

Selke etal. advantageously used rhodium(I) for the protection of add-labile phosphinite groups in order to cleave an benzylidene acetal in the backbone of carbohydrate bisphosphinite ligands (Eq. 3) [17]. 

The hydrocyanation of vinylarenes ° has been studied by a DuPont team using nickel catalysis. The hydrocyanation of 6-methoxy-2-vinylnaphthalene (2.219) affords the product (2.220), where the enantiomeric excess is strongly dependent upon the electronic nature of the bisphosphinite ligand (2.12). Hydrolysis of the nitrile (2.220) affords the nonsteroidal anti-inflammatory drug Naproxen. This nickel-catalysed procedure has also been applied with some success to the regiose-lective, asymmetric hydrocyanation of 1,3-dienes such as 1-phenyl-1,3-butadiene (2.221) to give the 1,2-adduct (2.222) with ees between 50 and 83%. ... 

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