Rhodium aldehyde arylation

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. 

Scheme 8.20 Phosphine versus diene in the rhodium-catalyzed arylation of a, 3-unsaturated aldehyde 91.

In 2010, Hu and coworkers [14] reported an interesting innovation regarding the rhodium-catalyzed aryl addition to aldehydes. Using 2-formylbenzoates as substrates and arylboronic acids, 3-substituted phthalides were efficiently obtained with rhodium-spinol-based phosphites... 

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... 

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

Oxidative addition of RX to bis[dicarbonylrhodium(I)] porphyrins [317] (see Eq. 28) or monorhodium(I) porphyrins (Scheme 3, path m) also produces (T-bonded complexes. The organic substrates RX include aldehydes, anhydrides, aryl or acyl, arylcarbonyl, or ethoxycarbonylmethyl halides, cyclopropyl ketones [62] or highly strained cyclopropanes [318]. The fate of the second rhodium ion formulated as [Rh(CO)2]+ in Eq. (28) was not investigated. 

Various rhodium(i) complexes catalyze the addition reaction of aryl- and 1-alkenylboronic acids to cr,/3-unsaturated ketones 489,935 936 4 93,941 and 495,937 aldehydes 490,938 esters 491 939 and 493 940 lactones 494,941 and amides 492942 in an aqueous solvent (Scheme 36). 

The addition of aryl- or 1-alkenylboronic acids to aldehydes was found to be catalyzed by rhodium(i) complexes via insertion of C=0 bond into the C-Rh intermediate generated by transmetallation (Equation (222)). The... 

The addition of arylboronic acids to imines in an aqueous solvent gave a mixture of amine (Eq. 6) and alcohol (Eq. 4) because the imines were partially hydrolyzed to the aldehyde during the reaction. The use of Ph4BNa in place of phenylboronic acid allowed the catalytic addition to various N-sulfonyl imines in the absence of water (Eq. 6). The representative results are summarized in Table 5. The cationic rhodium complexes such as [Rh(cod)(MeCN)2]BF4 was found to be the most efficient catalyst for both aromatic and aliphatic N-sulfonyl imines whereas no reactions were observed for N-alkyl and N-aryl imine derivatives. 

Ketones can be prepared from aryl aldehydes (ArCHO) by treatment with a rhodium complex (Ph3P)2Rh(CO)Ar, whereby the Ar group is transferred to the aldehyde, producing the ketone, Ar-CO-Ar. In a rhodium catalyzed reaction, aryl aldehydes (ArCHO) react with Me3SnAr to give the diaryl ketone Ar-CO-Ar. ... 

---