Photosensitized Intramolecular [2+2] Cycloaddition of 1HPyrrolo[2,3b]pyridines Enabled by the Assistance of Lewis Acids [component]

The [2+2] photocycloaddition of alkenyl-tethered 1H-pyrrolo[2,3-b]pyridine derivatives sensitized with 3',4'dimethoxyacetophenone under irradiation by a high-pressure mercury lamp through Pyrex glass was dramatically accelerated by the addition of Lewis acids, preferably Mg(OTf)2, to give the products stereoselectively in high yields. The reaction without a Lewis acid gave only small amounts of the [2+2] cycloaddition products. Conformational fixation of the substrates by coordination with a
more » ... is acid was presumed to facilitate the cycloaddition.
doi:10.1021/acs.joc.0c02231.s001 fatcat:natg64q6kbcblbj275zyhnt5be