Exploiting π shielding interactions of η6 arene chromium (0) complexes: New auxiliaries derived from the biogenic chiral pool

A family of highly selective chiral auxiliaries containing arene chromium (0) complexes has been prepared using biogenic precursors from the chiral pool. The systems, derived from isomannide, prolinol, and xylofuranose were applied to the asymmetric Diels–Alder reaction of derived acrylate esters. Factors influencing stereoselectivity with the auxiliaries have been investigated and delineated including the impact of mixed ligands on the chromium (0) complex. Under optimal conditions, the auxiliaries give >95% e.e. and 98:2 exo:endo ratio in cycloaddition with cyclopentadiene.

Highly selective chiral auxiliaries, designed on the basis of π shielding capability of arene chromium (0) complexes have been prepared from readily available building blocks. Cycloaddition diastereoselectivity as high as 99% was attainable using polymer–metal supported variants.Figure optionsDownload as PowerPoint slide