Efficient asymmetric synthesis of alpha-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 alpha-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.
Enders
D
D
Institute of Organic Chemistry, RWTH Aachen, Aachen, Germany. enders@rwth-aachen.de
Nühring
A
A
Runsink
J
J
D000438:Alcohols / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D003512:Cyclohexanones / Q000138:chemical synthesis* / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D019815:Oxalic Acid / Q000737:chemistry; D013237:Stereoisomerism
D000438:Alcohols; D003512:Cyclohexanones; D019815:Oxalic Acid