Effects of counter cations of base catalysts on nitrosation mechanisms

Reaction of 2-butanone (1) with tert-butyl nitrite (tert-BuONO) was performed using base catalysts (RO-M+: R=CH3, C2H5; M+=Li+, Na+, K+) in alcohols (CH3OH or C2H5OH). In this report, the effects of M+ of RO-M+ on the nitrosation mechanisms were investigated. The yield of E-hydroxyimino compound (5E) increases much better in the reaction using Na+ or K+ as M+ compared with that using Li+. It is also observed that the yield of 5E increases by addition of crown ether as a cation-capturing agent. The experimental results suggested that under the conditions lowering the effects of M+ of RO-M+ on the nitrosation mechanisms, because the reactivity of naked enolate of I increases and the reaction in the C-N bond formation process tends to proceed via open-chain transition state without M+, the yield of 5E tends to increase.