Cyclopropanation versus carbon–hydrogen insertion. The influences of substrate and catalyst on selectivity

Reactions of diazoacetates with varying linkages from the diazo-carbon to a vinyl group, catalyzed by chiral copper(I) and rhodium(II) compounds, were examined for selectivity in their intramolecular reactions. Bis-oxazoline-ligated copper(I) has advantages for cyclopropanation that form medium-to-large rings. Dirhodium(II) carboxamidates have advantages for small-ring-fused cyclopropane compounds and for carbon–hydrogen insertion.