Azidosubstituted arylboronic acids: synthesis and Suzuki-Miyaura cross-coupling reactions

Arylboronic acids having a remote azido group were prepared from the corresponding azidosubstituted aryl bromides via lithiation and treatment with trialkyl borates. Preparative yields were achieved when the starting aryl bromides possessed ortho-alkoxy groups, which would stabilize the intermediate aryllithium species. Conventional Suzuki cross-coupling of the arylboronic acids proceeded generally well with retention of azido group; however, sometimes azidomethyl fragment underwent oxidative transformation into a nitrile.     

Palladium-catalyzed cross-coupling reactions of 2-diazonaphthoquinones with arylboronic acids

Palladium-catalyzed cross-coupling reactions of 2-diazonaphthoquinones and arylboronic acids proceeded by the treatment with Pd(OAc)₂ in acetic acid to afford 2-aryl-1-naphthols.     

Synthesis of diarylmethane derivatives from Pd-catalyzed cross-coupling reactions of benzylic halides with arylboronic acids

A simple catalyst precursor prepared in situ from palladium acetate and triphenylphosphine shows high activity for the Suzuki cross-coupling reaction of benzylic bromides and chlorides with aryl boronic acids. The reaction can be carried out at low catalyst loading (0.002-1 mol%) and under mild conditions (room temperature to 80 °C) furnishing diarylmethane derivatives in high yields (86-99%).     

The palladium-catalyzed cross-coupling reaction of carboxylic anhydrides with arylboronic acids: a DFT study

The mechanism of the cross-coupling of phenylboronic acid with acetic anhydride, a viable model of the widely used Suzuki reaction, has been studied by DFT calculations at the BP86/6-31G level of theory. Two alternative catalytic cycles have been investigated, one starting from a neutral Pd(0)L(2) complex, the other from an anionic "Jutand-type" [Pd(0)L(2)X](-) species. The reaction profiles are in good agreement with the experimental findings, as both pathways require only moderate activation energies. Both pathways are dominated by cis-configured square-planar palladium(II)diphosphine intermediates. Despite careful investigations, we did not find in this model reaction any evidence for five-coordinate palladium(II) intermediates, which are commonly believed to cause the profound effects of counterions in palladium-catalyzed transformations. Instead, our calculations suggest that the higher catalytic activity of anionic complexes, such as [Pd(PMe(3))(2)OAc](-), may arise from their stronger ability to coordinate to carbon electrophiles. The transmetalation sequence is the same for both catalytic cycles, involving the dissociation of one phosphine ligand from the palladium. In the decisive transition state, in which the phenyl group is transferred from boron to palladium, the acetate base is found to be in a bridging coordination between these two atoms.     

Palladacycle-catalyzed cross-coupling reactions of arylboronic acids with carboxylic anhydrides or acyl chlorides

The triphenylphosphine–cyclopalladated ferrocenylimine (Cat. 2) exhibited highly catalytic activity for the both of arylboronic acids with carboxylic anhydrides and acyl chlorides with low catalyst loading (0.5 mol %). The reactions were unaffected by the presence of electron-releasing and electron-withdrawing substituents in both the arylboronic acids and carboxylic derivatives. Up to 98% yield was obtained for 32 examples. However, they were limited for arylboronic acid with strong electron-withdrawing groups. It is noting that catalyst 2 can be reused for eight times without losing its catalytic activity.     

Room-temperature Ni0-catalyzed cross-coupling reactions of aryl arenesulfonates with arylboronic acids

Room-temperature Ni(0)-catalyzed cross-coupling reactions of aryl arenesulfonates with arylboronic acids are described. The Ni(0) catalyst, derived from Ni(COD)2 and PCy3, proved to be a general one for the Suzuki-Miyaura cross-coupling of a variety of aryl arenesulfonates. The mild reaction condition, the readily availability of the catalyst, and excellent coupling yields make aryl arenesulfonates potentially useful substrates in organic synthesis.     

Triarylantimony dicarboxylates as pseudo-halides for palladium-catalyzed cross-coupling reaction with arylboronic acids and triarylbismuthanes without any base

The reaction of triarylantimony diacetates (6) with organoboron reagents (9) in the presence of Pd(PPh₃)₄ led to the formation of cross-coupling products, biaryls (10, 12 and 14-17), in moderate to excellent yields under mild conditions without any base. Similar reaction of 6 with triarylbismuthanes (18) also gave the corresponding cross-coupling products. Single crystal X-ray analysis of tri(p-tolyl)antimony diacetate (6b) and tris(p-trifluoromethylphenyl)antimony diacetate (6e) revealed the geometry of both central antimony atoms being intermediate between trigonal bipyramidal and pentagonal bipyramidal arrangement with intramolecular coordination between the antimony and two carbonyl oxygen atoms with cis orientation.     

Synthesis of arylketones by ruthenium-catalyzed cross-coupling of aldehydes with arylboronic acids

The first ruthenium-catalyzed cross-coupling of aldehydes with arylboronic acids is reported. Various aliphatic and aromatic aldehydes are transformed to the corresponding arylketones. A total of 31 examples with moderate to excellent yields are presented, together with the results of an initial mechanistic investigation.     

Fluorenone synthesis by palladacycle-catalyzed sequential reactions of 2-bromobenzaldehydes with arylboronic acids

A new, anionic four-electron donor-based (type I) palladacycle-catalyzed sequential reaction of 2-bromobenzaldehydes with arylboronic acids based on the addition reaction, cyclization via C-H activation-oxidation sequence is described. Our study provided an efficient access to a variety of substituted fluorenones/indenofluorenediones from readily available arylboronic acids and 2-bromobenzaldehydes.     

Synthesis of chiral quaternary fluorinated cyclic sulfamidates via palladium-catalyzed arylation with arylboronic acids

An enantioselective palladium-catalyzed arylation of fluorinated cyclic N-sulfonyl ketimines with arylboronic acids is described. This methodology provides an efficient and convenient route to chiral quaternary fluorinated cyclic sulfamidates in high yields with up to 99% ee.     

A base-free, one-pot diazotization/cross-coupling of anilines with arylboronic acids

Pd-catalyzed one-pot diazotization/cross-coupling is realized for the synthesis of biaryls directly from anilines and arylboronic acids.     

Diaminophosphine oxides as preligands for Ni-catalyzed Suzuki cross-coupling reactions of aryl chlorides with arylboronic acids

The first investigation of air- and moisture-stable diaminophosphine oxides as preligands in the Ni-catalyzed Suzuki cross-coupling reactions of aryl chlorides with arylboronic acids has been reported. The results show that under the optimized reaction conditions, the new catalytic system with a Ni(II) σ-aryl complex as precatalyst and a diaminophosphine oxide as preligand tolerates a variety of functional groups and is efficient for both electron-rich and electron-deficient aryl chlorides, though it shows higher efficiency for activated arylboronic acids than deactivated ones. Steric effects were observed for both aryl chlorides and arylboronic acids.     

Synthesis of new 8-arylisoquinoline derivatives by application of palladium-catalyzed Suzuki cross-coupling reactions

New 8-(het)aryltetrahydroisoquinolines (10-14), 8-aryltetrahydroisoquinolin-4-ols (15,16), and 8-phenylisoquinolin-4-ol (17), flexible analogues of aporphine, were synthesized in good yields using palladium-catalyzed Suzuki cross-coupling reactions from 8-bromotetrahydroisoquinolin-4-one (6) as a common intermediate. We also describe the synthesis of this novel intermediate through an easy and efficient method, which involved intramolecular Friedel-Crafts cyclization.     

Synthesis of substituted tetralones as intermediates of CNS agents via palladium-catalyzed cross-coupling reactions

A series of substituted tetralones as intermediates of CNS agents has been synthesized via Pd-catalyzed coupling reactions of 3-(methoxycarbonyl)-1,2,3,4-tetrahydro-1-oxonaphthalen-6-yl trifluoromethanesulfonate (5) with a variety of organometallic reagents.     

Synthesis of novel steroid analogues containing nitrile and disulfide moieties via palladium-catalyzed cross-coupling reactions

Grundmann's ketone (3) was used as a common building block for introduction of the C+D ring motif of steroids to prepare series of novel secosteroids containing nitrile or disulfide functionalities. Key steps in synthesis of these novel steroid analogues are palladium-catalyzed cross-coupling reactions. All target compounds were characterized by comprehensive analysis; in particular the stereochemical assignments of dinitriles 12a and 12b could be carried out in detail by NMR experiments. The pharmacological potential of all compounds was initially verified by a cytotoxicity test.     

Palladium-catalyzed carbonylative cross-coupling reaction of triarylantimony dicarboxylates with arylboronic acids: Synthesis of biaryl ketones

A novel palladium-catalyzed three-component carbonylative coupling reaction by use of triarylantimony diacetate, arylboronic acid and carbon monoxide (1 atm) could be attained under mild reaction conditions without any base as an additive. The reaction can be applied to a wide range of triarylantimony diacetates and boronic acids to afford the corresponding unsymmetrical biaryl ketones in good yields.     

Regioselective lithium-halogen exchange and palladium-catalyzed cross-coupling reactions of 2,4-dihaloquinolines

Lithium-halogen exchange of 2,4-dibromoquinolines proceeds regioselectively at C-4 and affords 4-substituted quinolines on quenching with electrophiles. Palladium-catalyzed cross-coupling reactions of 2-bromo-4-iodoquinoline provide 4-substituted 2-bromoquinoline derivatives.     

Suzuki-Miyaura cross-coupling of heteroaryl halides and arylboronic acids in continuous flow

General continuous-flow conditions for the Suzuki-Miyaura cross-coupling of heteroaryl halides and (hetero)arylboronic acids have been developed. A wide range of heterobiaryl products is obtained in excellent yields (20 examples) employing low catalyst loadings (0.05-1.5 mol % Pd).     

Successive substitution of halogen atoms in 4, 6-dihaloquinolines in palladium-catalyzed reactions with amines and arylboronic acids

A procedure was developed for the synthesis of 4,6-diamino- and 4,6- or 6,4-arylaminoquinolines by palladium-catalyzed C-N- and/or C-C-cross-coupling of 6-bromo-4-chloroquinoline.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 210–214, January, 2005.     

Preferential oxidative addition in palladium(0)-catalyzed suzuki cross-coupling reactions of dihaloarenes with arylboronic acids

The study of Pd(0)-/t-Bu3P system as a powerful catalyst for the cross-coupling of n,m-dihaloarenes with 1 equiv of arylboronic acids is described. Our work demonstrated that the fate of the regenerated Pd(0) catalyst can be controlled when the appropriate ligand is employed. The results described here may lead to the development of new, efficient processes to conjugate polymers with controlled length which are potentially useful in molecular electronics.