Rhodium-catalyzed carbozincation of ynamides using diorganozinc reagents or functionalized organozinc halides is described. Using a tri(2-furyl)phosphine-modified rhodium catalyst, the reaction course is altered to hydrozincation when diethylzinc is employed as the organozinc reagent. Trapping of the alkenylzinc intermediates produced in these reactions in further functionalization reactions is possible. Collectively, these processes enable access to a range of multisubstituted enamides in stereo- and regiocontrolled fashion.

Annulation of ynamides with arylboronic acids or esters containing an electrophilic functional group at the ortho-position proceeds under the action of rhodium catalysis to generate 2-amidoindenols or 2-amidoindenes, usually with good regioselectivity.

Co(acac)2.2H2O serves as an effective precatalyst for alkylative aldol cyclizations of alpha,beta-unsaturated amides with ketones using trialkylaluminum reagents. These reactions provide beta-hydroxylactams containing three contiguous stereocenters with high levels of diastereoselection.

Pyridine derivatives R 0380Diastereoselective Cobalt-Catalyzed Alkylative Aldol Cyclizations Using Trialkylaluminum Reagents. -The highly diastereoselective reaction of β-substituted α,β-unsaturated amides affords β-hydroxylactams bearing three contiguous stereocenters. Among the trialkylaluminum species tested, AlEt3 is shown to be most reactive. In some cases, reductive aldol products are also obtained. The substrate (XI) with a pendant phenyl ketone produces the desired hydroxylactam as a 1:1 mixture of stereochemically undefined diastereomers. -(RUDKIN, M. E.; JOENSUU, P. M.; MACLACHLAN, W. S.; LAM*, H. W.; Org. Lett. 10 (2008) 14, 2939-2942; Sch. Chem., Univ. Edinburgh, Edinburgh EH9 3JJ, UK; Eng.) -R. Steudel 48-137