Efficient asymmetric synthesis of α-alkylated 1,4-cyclohexanedione derivatives, important chiral building blocks in the synthesis of natural products

Alkylation of 1,4-cyclohexanedione monoethylene acetal SAMP-hydrazone with various electrophiles (10 examples given) and subsequent cleavage of the hydrazones with saturated oxalic acid furnished highly enantiomerically enriched α-alkylated mono-protected 1,4-cyclohexanedione derivatives in high yields and enantiomeric excesses of ee = 28, 80–≥99%. Reduction of the ketones gave the corresponding alcohols in good yields with high enantiomeric excesses (ee = 80–≥98%) and cis/trans-ratios of usually 85:15. Chirality 12:374–377, 2000. © 2000 Wiley-Liss, Inc.