Rh-catalyzed conjugate addition

Recently, Li and co-workers also reported the Rh-catalyzed arylstannane addition to enones in water under reflux.139 The addition of KOH helps the reaction to proceed smoothly (Scheme 50). A tentative mechanism was proposed for the Rh-catalyzed conjugated addition of phenyltin trichloride under basic conditions (Scheme 51). Later, this kind of reaction was found to work even in water at 50 °C. 

Similar 7i-allyl intermediates were proposed in Rh-catalyzed conjugate addition of phosphido groups to enones [87-89]. SUylphosphine substrates were suggested to generate Rh-phosphido intermediates from a Rh-OH catalyst precursor. Nucleophilic attack at the alkene, accompanied by formation of a Rh-7t-oxyallyl group, could be followed by protonolysis to yield the phosphine-ketone and regenerate a rhodium hydroxide. To differentiate this mechanism, in which only the Rh(l) oxidation state is involved, from one in which P-Si oxidative addition to yield Rh... 

Scheme 54 Proposed mechanism of Rh-catalyzed conjugate addition to enones...

Scheme 5.2 Rh-catalyzed conjugate addition of arylboronic acids to enones [10],...

Scheme 5.15 Rh-catalyzed conjugate addition of organotin compounds to a,fi-unsaturated carbonyl compounds as described by Oi and coworkers [59],...

Pd- and Rh-catalyzed conjugate additions of arylboronic acids to enones and nitrostyrenes (Hayashi-Miyaura reaction)... 

Scheme 2.12 Catalytic cycle for Rh-catalyzed conjugate addition of arylboronic acid to the acyclic enone.

This synthesis is based upon the Rh-catalyzed conjugate addition of aminophenyl boronates to the enone followed by cyclization to the 3,4-dihydroquinoline 112 and its... 

The dimerization of TIPS-acetylene in the Rh-catalyzed conjugate addition can be further minimized by employing the TIPS-acetylene elaborated with an alkynylsilanol group and an improved reaction protocol (eq 30). In the same report, this new protocol was applied to conjugate alkynylation of cyclic enones (eq31). 

Reetz MT, Moulin D, Gosberg A. BINOL-based diphos-phonites as ligands in the asymmetric Rh-catalyzed conjugate addition of arylboronic acids. Org. Lett. 2001 3 4083 085. 

Seheme 11.59 Selective addition to an a,p-unsaturated ketone vs. an a,p-unsaturated amide in a Rh-catalyzed conjugate addition reaction. 

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