A general method for the preparation of 3-substituted nitrocycloalkenes has been developed. 2-Nitrocyclo-alkanones are transformed into either α-nitro N,N-dimethylhydrazones or α-nitro cyclohexylimines, which exist exclusively in the oci-nitro form. Double deprotonation of these materials with sec-BuLi produces highly reactive dianions which can be alkylated with methyl, allyl, n-butyl, isopropyl, or 4-hexenyl iodides in excellent yields. The alkylation occurred uniformly next to the hydrazone or imine function. The alkylated α-nitro hydrazones are converted to nitroalkenes by reduction with NaBH4 followed by elimination induced by heating (120 °C) with acetic anhydride. The alkylated ?-nitro imines undergo facile reduction-elimination with NaBH4/CeCl3at room temperature. The overall yield for 2-nitro ketone to nitroalkene transformation ranged from 35% to 44% for the hydrazone method and from 19% to 39% for the imine method.
ASJC Scopus subject areas
- Organic Chemistry