Aptitude to ring expansion in the piperidine series, measured by the ratio of ring expanded ketone to epoxide, varies considerably according to the nitrogen atom substituent. This ratio is essentially the same in the case of the reaction of diazomethane on 4-piperidones and the nitrous acid deamination of the corresponding aminoalcohols. The values of the ratio are 0.01–0.1 for a phenylsulfonyl group, of the order 0.3–0.6 for a benzoyl group and slightly greater than 1 for a benzyl group. Electronic effects (inductive and field effects) are the cause of these differences. Parallels between the two reactions indicate that nucleophilic attack of diazomethane on the carbonyl group can lead to the ring expanded ketone and the epoxide.
在哌啶系列中,环扩张的能力,即环扩张酮与环氧化物的比率,根据氮原子取代基而有很大差异。这个比率在二氮化甲烷对4-哌啶酮的反应和相应氨基醇的亚硝酸脱氨反应中基本相同。对于苯磺酰基而言,这个比率为0.01-0.1,对苯甲酰基则为0.3-0.6左右,对苄基则略大于1。这些差异的原因是电子效应(归结效应和场效应)。这两种反应之间的类比表明,二氮化甲烷对羰基的亲核进攻可以导致环扩张酮和环氧化物的生成。