Highly strained, four-membered 1,2-diazetidine rings are produced in good yields (50–98%) in nucleophilic ring closure reactions provided ‘soft’ leaving groups such as iodide are used, a finding that can be rationalised in terms of the Hard Soft Acids and Bases principle.
如果使用“软”离去基团(如
碘化物),亲核开环反应中产生的高应变四元1,2-二氮杂
环丁烷环的收率很高(50-98%),这一发现可以合理地解释为硬质软酸和碱原理。