Effects of counter cations of base catalysts on nitrosation mechanisms

Reaction of 2-butanone (1) with tert-butyl nitrite (tert-BuONO) was perform ed 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 nitrosa tion 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 addi tion of crown ether as a cation-capturing agent. The experimental results s uggested that under the conditions lowering the effects of M+ of RO-M+ on t he nitrosation mechanisms, because the reactivity of naked enolate of 1 inc reases 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 increa se.