Ring opening reactions of 2-trialkylsilylaziridines

2-Trialkylsilylaziridines do not readily undergo nucleophilic ring opening without electrophilic assistance. In the presence of strong acids protonation at the nitrogen is followed by nucleophilic attack alpha to the silicon. With non-nucleophilic counterions, the protonated aziridine can be obtained. N-Alkylation gives the aziridinium salt, which also undergoes alpha-cleavage. However, the presence of a 3-phenyl substituent gives a stable aziridinium salt that undergoes nucleophilic attack beta to the silicon. Reaction of 2-trialkylsilylaziridines with trialkylsilyl halides usually leads to alpha-cleavage, however, desilylation to give the enamine is also observed. Fluorodesilylation of the 2-trialkylsilylaziridine is not straightforward and only occurred readily when a 2-ethoxycarbonyl group was present. Fluorodesilylation followed by attack on a carbonyl was only observed when very dry samples of fluoride ions were employed.