Rhodium complexes arylation

This catalytic reaction was believed to proceed analogously to those with phenylboronic acids (Scheme 49) 137 137a Transmetallation of the arylstannane with the cationic rhodium complex generated the rhodium aryl species a and trimethyltin tetrafluoroborate. Conjugate addition generated rhodium enolate b, which subsequently reacted with... 

Alkylative aldol reactions with aryl- or vinylboron reagents are also catalyzed by rhodium complexes.404 4043 4041 Equations (54) and (55) show examples of enantioselective reactions. 

Reactions of aryl- and styrylboronic acids with acid anhydrides are catalyzed by rhodium complexes to give ketones... 

Cationic rhodium complexes of these ligands were prepared and applied in the enantioselective hydroboration-oxidation of a range of vinylarenes,106,107 carefully chosen to highlight the effect on reactivity and enantioselectivity of different aryl substituents and / -substitution. Like QUINAP 60 and PHENAP 65, the ( -ligand gave rise to the (A)-secondary alcohol. 

Cluster or bimetallic reactions have also been proposed in addition to monometallic oxidative addition reactions. The reactions do not basically change. Reactions involving breaking of C-H bonds have been proposed. For palladium catalysed decomposition of triarylphosphines this is not the case [32], Likewise, Rh, Co, and Ru hydroformylation catalysts give aryl derivatives not involving C-H activation [33], Several rhodium complexes catalyse the exchange of aryl substituents at triarylphosphines [34] ... 

Investigation using P NMR revealed that a direct transmetallation of the phenyl group from boron to rhodium of the (oxa-n -aUyl)rhodium complex is involved in the reaction of B-Ph-9BBN. The catalytic cycle consists of two steps 1) insertion of the en-one into the aryl-rhodium bond and 2) transmetallation to the (oxa-7r-aUyl)rhodium complex forming an arylrhodium species and the boron enolate (Scheme 3.19). Unfor-... 

Rhodium complexes are able to transform various enynes 1 into the corresponding bi-cyclopentenones 2 with equal efficiency to that found with cobalt, and facilitate previously formidable PK reactions. The scope of the substituents on the alkyne for the intramolecular reaction is broad alkyl la/b and aryl-substituted substrates Ic provide the desired products in excellent yield with both [RhCl(CO)2]2 and [RhCl(CO)dppp]2 (Tab. 11.3). 

The same authors recently described the synthesis of similar rhodium-complexed dendrimers supported on a resin having both interior and exterior functional groups. These were tested as catalysts for the hydroformylation of aryl alkenes and vinyl esters (52). The results show that the reactions proceeded with high selectivity for the branched aldehydes, with excellent yields, even up to the tenth cycle. The hydroformylation experiments were carried out with first- and a second-generation rhodium-complexed dendrimers as catalysts, with a mixture of 34.5 bar of CO and 34.5 bar of H2 in dichloromethane at room temperature. Each catalyst was easily recovered by simple filtration and was reusable for at least six more cycles without... 

Hashimoto and co-workers (55) reported that generation of ylide 152 from aryl ester 151 in the presence of a chiral rhodium complex Rh2(S-PTTL)4, a chiral phthalimide substimted carboxylate, followed by cycloaddition with DMAD, led to the formation of adduct 153 in good yield and in 74% enantiomeric excess (ee). 

In 2003, Hayashi and his co-workers found that highly enantioselective rhodium-catalyzed allylic alkylation took place with l-aryl-2-propenyl acetates by using an achiral /3-diketonate ligand for the rhodium complexes in the presence of (diphenylphosphino)binaphthyloxazoline 60b. Fine-tuning of the /3-diketonate part resulted in enhancement in enantioselectivity up to 97% ee (Equation (49)). " ... 

Since Wakamatsu serendipitously discovered amidocarbonylation while performing the cobalt-catalyzed hydroformyla-tion of olefins in 1971, this unique carbonylation reaction, affording a-amino acids directly from aldehydes, has been extensively studied.More recently, palladium-catalyzed processes have been developed to expand the scope of this reaction.The Pd-catalyzed amidocarbonylation has been applied to aldehydes,aryl halides, and imines. As a related reaction, lactamization " of aryl halides catalyzed by a rhodium complex has also been developed. 

The chiral phosphine 31 or 32-rhodium complex catalyzed the addition of arystannanes 30 to N-sulfonylimines 29 to give diarylmethylamines 33 with high enantioselectivity (75-96% ee) [21]. The choice of the chiral monoden-tate phosphine ligand is essential for their catalytic asymmetric arylation. With chelating bisphosphine ligands the arylation was very slow. The authors hypoth-... 

Aryltrimethylstaimanes arylate aldehydes in the presence of a cationic rhodium complex, [Rh(cycloocta-l,5-diene)(MeCN)2]+, yielding secondary alcohols.114... 

In (C5Me5)Rh(C2H3SiMe3)2-catalyzed C-H/olefin coupling the effect of the coordination of the ketone carbonyl is different from that in the ruthenium-catalyzed reaction [10], In the rhodium-catalyzed reaction all C-H bonds on the aromatic ring are cleaved by the rhodium complex without coordination of the ketone carbonyl. Thus, C-H bond cleavage and addition of Rh-H to olefins proceed without coordination of the ketone carbonyl. After addition of the Rh-H species to the olefin, a coordinatively unsaturated Rh(aryl) (alkyl) species should be formed. Coordination of the ketone carbonyl group to the vacant site on the rhodium atom leads... 

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