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부분입체선택적 Zwitterionic Claisen 전위반응
柳燦模,崔夏洵,李宗昊,鄭元爀 성균관대학교 기초과학연구소 1995 論文集 Vol.46 No.2
Aza-Claisen rearrangement through the zwitterionic intermediate is described. This reaction was able to carry out at low temperature(-78∼0℃) and also exhibited high diastereoselectivities. The formation of zwitterionic intermediate was realized by addition of t-crotylamine to the ketene formed from deprotonation of corresponding acyl halide. The electronically neutral product was achieved through the [3,3]-sigmatropic rearrangement of self-promoted zwitterionic intermediate in high diastereoselectivity due to lower reaction temperature. Treatment of N-crotylpiperidine with propionyl chloride in the presence of K_2CO_3 at 0℃ for 1 h gave threo selective(97 : 3) amide in 41% isolated yield.