The purpose of this study was to explore regioselectivity and stereoselectivity in the Paternò–Büchi reaction of pyrrole derivatives. The regioselective formation of a bicyclic oxetane in the Paternò–Büchi reaction of 2‐siloxypyrrole with benzophenone was reported for the first time, and a mechanism involving the distribution of the intermediary triplet diradicals was proposed to account for the regioselectivity of the reaction. Copyright © 2016 John Wiley & Sons, Ltd.

The regio-and stereo-selectivity of the photochemical [2+2] cycloaddition reaction of 2-(t-butyldimethylsilyloxy)-1H-pyrrole with enone derivatives are investigated. Regioselective formation of cyclobutanes was found in the intermolecular photochemical [2+2] cycloaddition reaction of the pyrrole derivative with cyclopentenone. In contrast, an oxetane rather than a cyclobutane product was selectively formed when 1,4-naphthoquinone was used as the enone. The reaction conditions were optimized to obtain the cycloadducts in high yields.