Synthesis and Characterization of Chiral Nitronic Esters via O-Alkylation of (4S,5R)-(+)-4-(1‘-Nitro-1‘-carbethoxymethyl)- 5-[(1R)-menthyloxy]-3,4-dihydro-2(5H)-furanone with Alkyl Halides

• Published in: Journal of organic chemistry 1996-08, Vol.61 (16), p.5523-5527
• Main Authors: Kang, Fu-An, Yin, Cheng-Lie, She, Shi-Wang
• Format: Article
• Language: English
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/jo951902z

A series of stable and enantiomerically pure alkyl nitronic esters are synthesized in good to excellent yields via O-alkylation of (4S*,5R)-(+)-4-(1‘-nitro-1‘-carbethoxymethyl)-5-[(1R)-menthyloxy]-3,4-dihydro-2(5H)-furanone (4a) with alkyl halides in the presence of K2CO3 and DMF at room temperature. Thus, nitronic esters are obtained for the first time from the alkali metal salt of a nitro compound and various alkyl halides, which refutes the traditionally held view that the reaction of alkyl halides with alkali metal derivatives of nitro compounds gives a carbonyl compound and an oxime, rather than a nitronic ester. Secondary alkyl nitronic esters are found to partially decompose into O-alkyloximes. The configurations of the nitronic esters and O-alkyloximes were assigned to be Z on the basis of the NOE experiments. The synthesis of the nitro furanone 4a and its enolization to form a six-membered intramolecular hydrogen bond structure are described.