Dynamically Generated Carbenium Species via Photoisomerization of Cyclic Alkenes: Mild Friedel-Crafts Alkylation.

The torsional strain of -configured medium-sized (6-8) cycloalkenes imparts substantial potential energy efficiently toward ionic additions through generated reactive carbenium species. These reactions have been underexplored due to a historical necessity for harsh ultraviolet irradiation. We report here the Friedel-Crafts (FC) type reactivity of arylcycloalkenes (ACs) and π-nucleophiles for the first time with weak Brønsted acid and visible light energy transfer catalysis.

Development of Transiently Strainable Benzocycloheptenes for Catalyst-Free, Visible-Light-Mediated [3 + 2]-Cycloadditions.

Dynamic photogeneration of ephemeral and reactive species is enabling for chemical reactions, providing spatial and temporal control. A previous study from our group established the ability of 6,7-dihydro-5H-benzo[7]annulene, benzocycloheptene (), to convert photochemical energy into ring strain, enabling the rapid cycloaddition of alkyl azides with the reversibly formed and transient -isomer, affording versatile nonaromatic triazolines. Despite the conceptual advances of the previous study, some challenges remained: the fragility of the triazoline products, the low regioselectivity for the cycloaddition, a need for an iridium-based photosensitizer and organic-based solvents, and a lack of convenient linchpin functional group handles.