Asymmetric halo aldol reaction (AHA).

[reaction: see text] The asymmetric halo aldol reaction (AHA) using Evans oxazolidinones as chiral auxiliaries has been established for tandem I-C/C-C bond formations. The new asymmetric reaction provides a practical approach to a variety of halo aldols of a non-Evans type that cannot be easily synthesized by other methods. Excellent diastereoselectivity (>95%) and yields (80-93%) have been obtained for eight examples.