Synthesis of biaryls

Another area of interest to the industrial sector is the development of a more efficient synthesis of biaryl compounds. This has been accompHshed using a Ni(II)-cataly2ed Grignard coupling reaction with an aryl haUde (86—89). 

Meyers has also reported the use of chiral oxazolines in asymmetric copper-catalyzed Ullmann coupling reactions. For example, treatment of bromooxazoline 50 with activated copper powder in refluxing DMF afforded binaphthyl oxazoline 51 as a 93 7 mixture of atropisomers diastereomerically pure material was obtained in 57% yield after a single recrystallization. Reductive cleavage of the oxazoline groups as described above afforded diol 52 in 88% yield. This methodology has also been applied to the synthesis of biaryl derivatives. 

Fluorous Synthesis of Biaryl-Subshtuted Proline Analogs. 112... 

Fluorous Synthesis of Biaryl-Substituted Proline Analogs... 

Fig. 30 Microwave-promoted fluorous synthesis of biaryl-subshtuted proline analogs. Reagents and condihons a EtaN, DMF, MW 150 °C, 15 min, 40-75%, closed vials b R""PhB(OH)2, Pd(dppf)Cl2, K3PO4, toluene Acetone H2O, MW 120 °C, 12 min, sealed vial system, 19-79%. R=Me, Et R = Me, 1 - Pr R" = H, 3-MeO R" =Me, Et R""= 4-MeO, 3-Cl, 4-Ac,3,4-diCl,3,4-methylenedioxy...

AN IMPROVED SYNTHESIS OF BIARYL DERIVATIVES VIA THE PALLADIUM CATALYZED COUPLING OF ARYL BROMIDES... 

The direct preparation of arylboronic esters from aryl halides or triflates now allows a one-pot, two-step procedure for the synthesis of unsymmetrical biaryls (Scheme 1-41) [147]. The synthesis of biaryls is readily carried out in the same flask when the first coupling of the triflate with diboron 82 is followed by the next reaction with another triflate. The synthesis of naturally occurring biflavanoids and the couphng of N-(phenylfluorenyl)amino carbonyl compounds to polymeric supports are reported [154]. 

Aromatic rings are moderately reactive toward addition of free radicals (see Part A, Section 12.2) and certain synthetically useful substitution reactions involve free radical substitution. One example is the synthesis of biaryls.175... 

Furanborinic acids have hardly been studied except for a report of their use in the synthesis of biaryls, e.g., 2-(2-thienyl)furan in 20% yield.238... 

The described fluorous-tag strategy has also been applied to the synthesis of biaryl-substituted hydantoins (Scheme 7.81) [94]. 4-Hydroxybenzaldehyde was converted into the corresponding perfluorinated species, which was then subjected to a reductive amination. The resulting amine was treated with an isocyanate to produce the fluorous-tagged urea, which spontaneously cyclized to form the corresponding hydantoin. Finally, the fluorous tag was detached by a Suzuki-type carbon-carbon bond formation to furnish the desired target structure in good yield. 

The directed synthesis of biaryls can be achieved using rhodium-based catalysts along with a phosphinite co-ligand (Equation (143)). 

For purposes of completeness, palladium-catalyzed reactions for the synthesis of biaryls using zincates and arylhalides (Negishi Couplings) [254] or using sihcon compounds [255, 256] need to be mentioned. 

The same methodological approach has been extended to the synthesis of biaryls [24]. Reaction (6.12) shows a few examples in which the transfers of functionalized aryl groups from silicon to aryl radicals are successful. A mechanistic scheme similar to that reported in Reaction (6.10) has been proposed. 

Synthesis of biaryls by Raney Ni-catalysed homocoupling of diaryltellurium dichlorides and aryltellurium trichlorides... 

Synthesis of biaryls (general procedure The diaryltellurium dichloride (50 mmol) is heated with degassed Raney nickeP (60 g) in diglyme (500 mL) for 8 h. The mixture is filtered while still hot, and the solvent evaporated (water pump). The residue is recrystallized from ethanol or toluene. 

Key components for the synthesis of biaryl ether macrocycles were diisonitriles 98 and 101. The former was synthesized in two steps (61% yield) from commercially available diamine 97 by bisformamide formation and subsequent dehydration with phosphorus oxychloride (Scheme 16). Starting ma-... 

Couplings can also be carried out by simple nucleophilic substitution reactions of arenechromium tricarbonyls . For example, in the synthesis of biaryl 469, asymmetric lithiation of 463 using in situ silylation provides the complex 466 via 464 and 465. Nucleophilic substitution by the tolyl Grignard 467 yields 468 as a single atropisomer in 68% yield, and decomplexation gives the biaryl 469 in 92% yield (Scheme 184). 

The synthesis of biaryl fluorophores exhibiting visible fluorescence will be the responsibility of the PI (Nat Finney) and will begin within a month. The synthesis and complete characterization of the proposed fluorophores are anticipated to take 6 months, in light of teaching, advising, and grant-writing responsibilities. 

SYNTHESIS OF BIARYLS VIA PALLADIim-CATALYZEO CROSS COUPLING Z-KTHYL-4 -NnH0BIPHENYL (1,1 -Biphenyl, Z- ethy1-4 -nitro-)... 

SYNTHESIS OF BIARYLS VIA PALLADIUM-CROSS COUPLING 2-METHYL-4 -NITR0BIPHENYL... 

By consideration of the intramolecular free radical / rn-substitution approach <1988TL2987> for the synthesis of biaryls, the direct [1,6]-addition product 184 was obtained in 63% yield from the corresponding -toluenesulfonyl derivative (Scheme 52) <1991CC877>. Under similar reaction conditions, the sultine 185 was available in 89% yield from the readily available substrate <2006AGE633>. 

One of the most useful aspects of the oxazoline-directed aromatic substitution is the synthesis of biaryls. This method nicely complements other well-known biaryl... 

SYNTHESIS OF BIARYLS VIA PALLADIUM-CATALYZED CROSS COUPLING 2-NETHYL-4 -NITROBIPHENYL (l.l -Biphenyl, 2-methyl-4 -nitro-)... 

Blettner, C. G. Konig, W. A. Stenzel, W. Schotten, T. Polyfethylene glycol) Supported Liquid Phase Synthesis of Biaryls, Synlett 1998, 295-297. 

Forman, F. W. Sucholeiki, I. Solid-Phase Synthesis of Biaryls via the Stille Reaction, J. Org. Chem. 1995, 60, 523-528. 

Saito, S. Oh-tani, S. Miyaura, N. Synthesis of biaryls via a Ni(0)-catalyzed cross-coupling reaction of chloroarenes with arylboronic acids./. Org. Chem. 1997, 62, 8024-8030. 

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