alpha,beta-unsaturated Fischer carbene complexes vs. 1,3-dipoles: Reactions with nitrones and nitrilimines

The reaction of tert-butylalkynyl chromium Fischer carbene complex 1 with n itrones 2 affords beta-enamino-ketoaldehydes 4 by the Light-promoted rearra ngement of the corresponding [3+2] cycloadduct carbene complexes 3. On the other hand, [3+2] cycloaddition of chiral nonracemic Fischer alkenyl carben e complexes 19 with nitrilimines 10 yields enantiomerically pure Delta(2)-p yrazolines with high regio- and diastereoselectivity.