Biaryl bisphosphine

Chan has discovered a completely atropdiasteroselective synthesis of a biaryl diphosphine by asymmetric intramolecular Ullmann coupling or Fe(m)-promoted oxidative coupling. A chiral atropisomeric biaryl bisphosphine ligand 2 was synthesized through this central-to-axial chirality transfer.38 Recently, a xylyl-biaryl bisphosphine ligand, Xyl-TetraPHEMP, was introduced by Moran, and is found to be effective for the Ru-catalyzed hydrogenation of aryl ketone.39... 

This chapter describes atropisomeric biaryl bisphosphine ligands modified DIOP-type ligands P-chiral bisphosphane ligands other bisphosphane ligands and their applications in the enantioselective hydrogenation of olefins. 

Atropisomeric biaryl bisphosphines, in hydrogenation, 10, 2 Atropisomerism, dynamic NMR studies, 1, 421 ATRP, see Atom transfer radical polymerization type reactions rj3-l-Azaallyl complexes, with nickel, 8, 158 6-Aza[3.2.1]bicyclooct-3-ene, via ring-closing metathesis,... 

Biaryl bisphosphines, atropisomeric, in hydrogenation, 10, 2 Biaryl-bridged bis(iminooxazolidine) complexes, with Zr(IV) and Hf(IV), 4, 811-812 Biaryl compounds, directed synthesis, 10, 145 Bicyclic arenes, in hexaruthenium carbido clusters,... 

The binaphthyl backbone of BINAP has inspired many variations of atropisomeric biaryl bisphosphines. One approach by Roche was to substitute the binaphthyl backbone with a 6,6 -dimethox-ybiphenyl backbone. MeO-Biphep (96a) was synthesized in approximately 26% yield in 6 steps from 3-bromoanisole (97a) (Scheme 12.30). MeO-Biphep can also be synthesized in 5 steps from 2-iodo-3-nitroanisole in approximately 18% yield. Several phosphine analogues can be prepared by the addition of R2PC1 to the lithio intermediate.117... 

Takasago has patented an alternate route to /-menthol (22) (Scheme 12.36).131 Chirality is set by the rhodium catalyzed asymmetric hydrogenation of piperitenone (108). Although many chiral biaryl bisphosphines catalysts have been used, DTMB-SegPHOS (107c) produced pulegone (109) in 90% yield and 98% ee with an S/C ratio of 50,000.131... 

The chiral biaryl bisphosphine ligand SEGPHOS 34, developed by Takasago, possesses a smaller dihedral angle than BINAP. The ligand has provided greater enantioselectivity over BINAP in Ru-catalyzed hydrogenation of a wide variety of carbonyl compounds.31... 

Biaryl bisphosphine reported by Consiglio and cataiyst reported by Sen for the copolymerization of carbon monoxide and propene to form syndiotactic CO/propylene copolymer. 

The success of Ru-BINAP complexes in hydrogenation processes promoted the development of many related atropisomeric biaryl bisphosphine ligands. 

In the intermolecular [2+2+2] cycloaddition of unsymmetiic monoynes, it is difficult to control its regioselectivity. Cationic rhodium(l)/biaryl bisphosphine complexes are highly active and selective catalysts for the 1,2,4-selective [2+2+2] cycloaddition of terminal alkynes (Scheme 21.3) [7]. However, unfortunately, a general and practical catalyst that enables the 1,3,5-selective [2+2+2] cycloaddition of terminal alkynes has not been developed. 

The apphcation of the rhodinm(l)-catalyzed double [2+2+2] cycloaddition approach to the synthesis of symmetric biaryl diphosphoms compounds was first accomplished in the reactions of l,4-bis(diphenylphosphinoyl)bnta-l,3-diyne with terminal diynes to give achiral biaryl bisphosphine oxides [23a]. Cj-Symmetric axially chiral biaryl diphosphonates were obtained with perfect enantioselectivity by using a phosphonate-substituted 1,3-bntadiyne and internal 1,6-diynes (Scheme 21.19) [23b]. Axially chiral biaryl dicarboxylates were also obtained by this method [23b]. 

The cationic rhodium(l)/axially chiral biaryl bisphosphine complex-catalyzed [2+2+2] cycloaddition of biaryl-linked tetraynes with dialkynylketones or dialkynylphosphine oxides afforded helically chiral l,l -bitriphenylenes, containing adensely substituted fluorenone or phosphafluorene core (Scheme 21.23) [27]. 

The intramolecular [2+2+2] cycloaddition of triynes affords tricyclic compounds, which are not readily accessible by other methods. The double [2+2+2] cycloaddition of a diphenylphosphinoyl-substituted hexayne proceeded in the presence of the cationic rhodium(I)/tol-BINAP catalyst to give the corresponding Cj-symmetric axially chiral biaryl bisphosphine oxide with high enantioselectivity (Scheme 21.24) [28]. 

In 2003, Tanaka et al. discovered that cationic rhodium(I)/biaryl bisphosphine complexes are highly active and selective catalysts for 1,2,4-selective intermolecular [2 + 2 + 2] cycloaddition of terminal alkynes (Scheme 4.9) [4], Furthermore, a cationic rhodium(I)/Hg-BINAP complex catalyzed chemo- and regioselective intermolecular cross-[2 + 2 + 2] cycloaddition of dialkyl acetylenedicarboxylate with two... 

The cationic rhodium(I)/biaryl bisphosphine complexes are also effective catalysts for partially intramolecular [2- -2-1-2] cycloaddition of 1,6-diynes with alkynes. It is worthy of note that the cationic rhodium(I)/Hg-BlNAP complex is able to catalyze [2-I-2-I-2] cycloaddition of usually less reactive 1,7-diynes with alkynes, giving functionalized tetrahydronaphthalenes (Scheme 4.41) [45a]. Importantly, these reactions proceeded smoothly without a Thorpe-Ingold effect [45b]. 

Cationic rhodium(I)/biaryl bisphosphine complexes are an effective catalyst for intermolecular [2 + 2 + 2] cycloaddition of alkynes with nitriles under mild conditions. The [2 + 2 + 2] cycloaddition of 1-dodecyne with ethyl cyanoacetate proceeded at 60 °C in the presence of the cationic rhodium(I)/BINAP catalyst to give trisubstituted pyridines in high yield with moderate regioselectivity (Scheme 4.53) [55]. 

The enantioselective desymmetrization of substituted malononitriles via cationic rhodium(I)/axially chiral biaryl bisphosphine-catalyzed [2 + 2 + 2] cycloaddition with a 1,6-diyne proceeded at room temperature to give enantio-enriched bicycUc pyridines in good yields with moderate ee values (Scheme 4.66) [55],... 

The enantioselective synthesis of C2-symmetric spirobipyridines were accomplished via the completely intramolecular double [2 + 2 + 2] cycloaddition of bis-diynenitriles by using [Rh(cod)2]BF4/axially chiral biaryl bisphosphine complexes as catalysts (Schemes 4.67 and 4.68) [58]. 

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