[reaction: see text] Mild Ni(0)-catalyzed rearrangements of 1-acyl-2-vinylcyclopropanes have been developed. The room-temperature isomerizations afford dihydrofuran products in yields regularly greater than 90%. A highly substituted, stereochemically defined cyclopropane was employed in the rearrangement to evaluate the reaction mechanism. Product analysis indicates that the overall reaction proceeds with retention of configuration at the vinyl-bearing stereogenic center.

Lewis acids are shown to cleave the carbon-carbon bond of activated aziridines at ambient temperature. The derived metal-coordinated azomethine ylides undergo cycloaddition reactions with electron-rich alkenes. Cyclic alkenes afford products that are formally [4+2] adducts most likely derived from a Mannich-type addition to the ylide, followed by intramolecular Friedel-Crafts alkylation. Alternatively, acyclic alkenes undergo [3+2] cycloaddition to give new pyrrolidine products.

An evaluation of simple Lewis acids revealed that N-malonylimidates undergo catalyzed [3+2] cycloaddition reactions with aldehydes, imines, and activated olefins to form oxazolines, imidazolines, and pyrrolines, respectively. Reactions proceed optimally at ambient temperature with the addition of 5 mol % of MgCl(2) in CH(3)CN. Experiments aimed at elucidation of the reactive intermediate undergoing cycloaddition suggest that the Lewis acid promotes a 1,2-prototropic shift to give a metal-coordinated azomethine ylide, rather than ionization and proton transfer to give a nitrile ylide.

High throughput screening enabled the development of a Cu-based catalyst system for the asymmetric hydrogenation of prochiral aryl and heteroaryl ketones that operates at H2 pressures as low as 5 bar. A ligand combination of (R,S)-N-Me-3,5-xylyl-BoPhoz and tris(3,5-xylyl)phosphine provided benzylic alcohols in good yields and enantioselectivities. The electronic and steric characteristics of the ancillary triarylphosphine were important in determining both reactivity and selectivity.