Bisphosphanes, synthesis

S,4S)-N-tert-butoxycarbonyl-4-diphenylphosphino-2-diphenylphosphino-methyl-pyrrolidine (BPPM) (13) is an excellent bisphosphane and is also the starting material for the synthesis of PPM (14). The chiral bisphosphanes (15) have been prepared by reaction of (14) with either acid chlorides or isocyanates. 

Scheme 2,1,4,32 Pd-catalyzed asymmetric synthesis of allylic alcohols in the presence of bisphosphane 34,...

The Pd-catalyzed allylic alkylation of sulfinate ions, thiols, and thiocarboxylate ions with racemic cyclic and acyclic allylic esters in the presence of bisphosphane BPA generally provides for an efficient asymmetric synthesis of allylic sulfones, sulfides, and thioesters. The Pd-catalyzed rearrangements of allylic sulfinates and allylic O-thiocarbamates, both of which proceed very efficiently in the presence of BPA, are attractive alternative ways to the asymmetric synthesis of allylic sulfones and allyUc thioesters also starting from the corresponding racemic alcohols. 

Phosphinoalkyl)phosphonium salts were first prepared through mono-quaternization of bisphosphanes in 1991 (44). The synthesis proceeds according to Eqs. (3) and (4). 

BPE, and chiral bisphosphane ligands, 10, 7 (+)-Brasilenyne, via ring-closing diene metathesis, 11, 221 Breast implants, silicone applications, 3, 680 Brevetoxin B, via ring-closing diene metathesis, 11, 237 m -Brevicomin, synthesis, 9, 13... 

Similar cts-bis-carbene chelate complexes of palladium(Il) [327,330,331], but without the hydroxy functional groups on the wingtips, were used by the same research group for the copolymerisation of ethylene and CO. Once again, chelating bisphosphane complexes inspired the synthesis and application of their NHC counterparts [332,333]. The actual, defined catalyst precursors were the cationic complexes formed after haUde abstraction with silver salts in acetonitrile as donor solvent. 

Although the first P-chiral bisphosphane (DIPAMP) was developed by Knowles over 30 years ago, the discovery of new efficient P-chiral bisphosphanes has been slow partly because of the difficulties in ligand synthesis. Pye and Rossen have developed a planar chiral bisphosphine ligand, [2.2]-PHANEPHOS 40, based on a paracyclophane backbone.37 The ligand has shown excellent enantioselectivity in Rh- and Ru-catalyzed hydrogenations. 

A substantial improvement on the above-described class of Ru-vinyUdene complexes has been achieved by Louie and Grubbs through synthesis of a novel generation of complexes coordinating an A-heterocyclic carbene (NHC) ligand (e.g. imidazolylidene). This new set of Ru complexes, e.g. 15 (IMes = l,3-(2,4,6-trimethylphenyl)imidazoT2-ylidene, R = Cy, R = t-Bu) and 16 (iPrlM = l,3-diisopropyl-4,5-dimethyl-imidazol-2-ylidene, R = Cy, R = Ph) has been conveniently produced from the bisphosphane-Ru complex 9 (R = Cy) by reaction with free imidazoline carbene or its precursor salts (Scheme 7). 

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