2-Cyanoazetidines and Azetidinium Ions: Scaffolds for Molecular Diversity

Ring strain in azetidines and azetidinium ions can be efficiently used to promote ring-expansion and ring-opening reactions, and this renders these four-membered heterocycles ideal scaffolds for diversity oriented synthesis. This microreview focuses on 2-cyanoazetidines, which are easily prepared from β-amino alcohols through a ring-closing reaction involving C–C bond formation. The azetidines can be readily expanded to five- to eight-membered nitrogen heterocycles after suitable functionalization and/or activation. Alternatively, N-alkylated derivatives, namely, azetidinium ions, are easily prepared and displayed rich reactivity as new electrophilic building blocks and as sources of nitrogen ylides.SCOPUS: re.jFLWIN