The palladium-catalysed Suzuki–Miyaura cross-coupling reaction of organohalides and organoborons is a reliable method for carbon–carbon bond formation. This reaction involves a base-mediated transmetalation process, but the presence of a base also promotes competitive protodeborylation. Herein, we established a Suzuki–Miyaura cross-coupling reaction via Lewis acid-mediated transmetalation of an organopalladium(II) intermediate with organoborons. Experimental and theoretical investigations indicate that the controlled release of the transmetalation-active intermediate enables base-independent transmetalation under heating conditions and enhances the applicable scope of this process. This system enables us to avoid the addition of a traditional base and, thus, renders substrates with base-sensitive moieties available. Results from this research further expand the overall utility of cross-coupling chemistry.

The combination of Et2Zn and RhCl(PPh3)3 led to the facile generation of a rhodium-hydride complex (Rh-H) that catalyzed the 1,4-reduction of α,β-unsaturated esters. The resulting rhodium enolate performed as a Reformatsky-type reagent and reacted with various imines to give syn-β-lactams in good to excellent yields with high diastereoselectivity.

The reaction of tris(triphenylphosphine)-with diethylzinc (Et 2 Zn) easily afforded a rhodium-hydride complex that effects the 1,4-reduction of a,b-unsaturated esters to give rhodium enolates. Formation of the rhodium enolate is followed by transmetalation with the zinc species to give a Reformatsky-type reagent, and this reacts with various acid chlorides at the aposition to give b-keto esters. The Reformatsky-type reagent also reacts with various electrophiles such as aldehydes, ketones and acid anhydrides to give the corresponding products in which the electrophiles were introduced reductively at the a-position of a,bunsaturated esters.

SummaryAn effective synthesis for syn-β-lactams was achieved using a Rh-catalyzed reductive Mannich-type reaction. A rhodium–hydride complex (Rh–H) derived from diethylzinc (Et2Zn) and a Rh catalyst was used for the 1,4-reduction of an α,β-unsaturated ester to give a Reformatsky-type reagent, which in turn, reacted with an imine to give the syn-β-lactam. Additionally, the reaction was applied to the synthesis of (±)-ezetimibe, a potent β-lactamic cholesterol absorption inhibitor.

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An asymmetric reductive aldol-type reaction of α,β-unsaturated esters with carbonyl compounds using Rh catalyst and Et 2 Zn was investigated. A chiral zinc complex from α,β-unsaturated ester was easily generated as the key intermediate from Et 2 Zn and Wilkinson's catalyst with diisopropyl L-( )-tartrate to give a variety of enantioenriched β-hydroxy esters. The reaction was also applied to the intramolecular reductive aldol cyclization.

Fluoroalkenes have shown importance as a metabolically stable isostere of amide compounds. To expedite the synthesis of diverse fluoroalkenes, we have developed a dual-reactive C2-unit, (Z)-1-boryl-1-fluoro-2-tosyloxyethene, containing nucleophilic and electrophilic moieties. Consecutive palladium-catalyzed cross-coupling reactions of this unit with aryl bromides and aryl boronic acids allow for the convergent synthesis of diverse trans-1,2-diaryl-substituted fluoroethenes in a chemoselective and stereoretentive manner.

Carbon-carbon bond formation is a fundamental transformation of synthetic organic chemistry. This minireview focuses on our works related to reductive aldol reaction, reductive Mannich reaction, reductive α-acylation, and reductive αcarboxylation by using rhodium catalyst to achieve CC bond formation. Rh-catalyzed reductive aldol reaction successfully gave-hydroxy carbonyl compounds from α,-unsaturated carbonyl compounds with aldehydes or ketones by treating with RhCl(PPh 3) 3 and Et 2 Zn. This condition could apply to other electrophiles such as imines, acid chlorides, and acid an-[a]