Reactivity and Selectivity in Catalytic Reactions of Enoldiazoacetamides. Assessment of Metal Carbenes as Intermediates

Catalyst effectiveness for metal carbene formation and reactions has been surveyed using N-(tert-butyl)-3-[(tert-butyldimethylsilyl)oxy]-2-diazo-N-(4-chlorobenzyl)but-3-enamide in the formation of the products from both intramolecular C–H insertion and aromatic cycloaddition. Both products are indicators of metal carbene intermediates, and this system provides a means to assess catalysts for metal carbene formation. Donor–acceptor cyclopropene production from the reactant enoldiazoacetamide has been monitored to assess its formation, and the independently formed cyclopropene has also been used to assess metal carbene formation. Catalysts of rhodium(II), copper(I), silver(I), Pd(II), cationic Au(I), and Zn(II) convert the enoldiazoacetamide to the donor–acceptor cyclopropene which serves as the resting state for the intermediate metal carbene, and both the enoldiazoacetamide and its derivative cyclopropene give the same ratios of insertion to cycloaddition products. Catalysts of copper(II) and ruthenium(II...