Ruthenacyclopentanes as Intermediates in the Regio- and Stereoselective Linear Codimerization ofN-Vinylamides with Electron-Deficient Alkenes

Abstract

Tricarbonylruthenacyclopentanes were successfully synthesized by in situ reduction of RuCl3 with Zn-Cu/CO in the presence of N-vinylacetamides and electron-deficient alkenes such as ethyl acrylate, dimethyl fumarate, and dimethyl maleate. X-ray crystallography of the ruthenacyclopentanes revealed that the three carbonyl ligands occupied coordination sites facially, and the ruthenacycle moiety was stabilized by coordination with the acetamido oxygen atom. When the ruthenacyclopentanes in toluene or DMA were heated to 130 °C for 24 h, linear codimers of the alkenes were formed in moderate to good yield. Both the ruthenacyclopentane and the RuCl3/Zn-Cu/alcohol system showed catalytic activity for the linear codimerization of alkenes, affording the codimers in good yield. The results of stoichiometric and catalytic reactions revealed that the codimerization can proceed via ruthenacyclopentane intermediates.

Recent Advances in the Catalytic Linear Cross-Dimerizations

“…Ura and co-workers also documented a ruthenacycle 90, supporting this mechanism (Scheme 15). 57 Contrary to the mechanism shown in Scheme 15, the same group reported the coupling reactions using the same substrates 52 and 87 catalyzed by a Ru(0) complex [Ru(η 6 -1,3,5-cot)(η 2 -dmfm) 2 ] to proceed by the hydride-insertion mechanism based on the deuterium labeling experiments. 58 One of the possibilities is that the mechanism varies according to the supporting ligand.…”

Catalysis with cycloruthenated complexes

“…ethyl acrylate, dimethyl fumarate, and dimethyl maleate) under a CO atmosphere ( Scheme 61A ). 103 The three CO ligands were found to coordinate in a fac fashion, with additional stabilisation provided by the coordination of the acetamide oxygen atom. The resulting complexes Ru109 were air- and moisture-stable, and were even amenable to purification by silica gel chromatography under ambient conditions.…”

In Situ Routes to Catalytically Active Ru(0) Species by Reduction of Readily Available, Air-Stable Precursors

“…Following the first brief report by Wittenberg of Co-catalyzed cross-dimerizations of dienes, various catalytic systems based on transition metal compounds from groups 10 to 8 have been reported (Table ). − We have documented regio- and enantioselective cross-dimerizations between conjugated dienes and substituted alkenes catalyzed by [Ru­(η 6 -naphthalene)­(η 4 -cyclic diene)] ( 1 ), where the cyclic diene ligand acts as an important ancillary ligand for the activity and selectivity. Typical examples are the cross-dimerization of 1,3-dienes with acrylates, the tail-to-tail dimerization of acrylates, and the chemo- and stereoselective cross-dimerization of methyl methacrylate or methacrylamide with unsaturated five-membered-ring compounds …”