Visible Light Photocatalysis of 6π Heterocyclization

Abstract

Photo-mediated 6p cyclization is avaluable method for the formation of fused heterocyclic systems.H ere we demonstrate that irradiation of cyclic 2-aryloxyketones with blue LED light in the presence of an Ir III complex leads to efficient and high yielding arylation across ap anoply of substrates by energy transfer.2 -Arylthioketones and 2-arylaminoketones also cyclizee ffectively under these conditions. Quantum calculation demonstrates that the reaction proceeds via conrotatory ring closure in the triplet excited state. Subsequent suprafacial 1,4-hydrogen shift and epimerization leads to the observed cis-fused products.

Energy transfer catalysis mediated by visible light: principles, applications, directions

“…Finally, the application of visible-light-mediated EnT catalysis in recently described by Smith and co-workers. 32 H derivatives (ET = ~58 kcal mol -1 ) were activated with fac-[Ir(dFppy)3] (ET = 63.5 kcal mol -1 ) under irradiation with blue LEDs and in the presence of a base (KOAc) to afford the cis-fused cyclization products 20 in generally excellent yield and with near perfect diastereoselectivity. Computational studies suggest that the reactions initiate via EnT and the formation of triplet intermediates 18*, which following conrotatory heterocyclization and ISC afford open-shell singlet intermediates 19.…”

Visible‐Light‐Promoted Polycyclizations of Dienynes

“…The mechanism of these domino sequences was studied by DFT calculations to rationalize the formation of the observed products (Scheme ). Optimizations were carried out without constraints at the M06/Def2‐tzvp level of theory, which is able to accurately reproduce experimental ET potentials and eT energies, with DMF as the implicit solvent (see the Supporting Information for details). We modeled cationic, radical, radical cationic, and anionic species, and checked multiplicities up to quintet states.…”

Chromophore Activation of α,β‐Unsaturated Carbonyl Compounds and Its Application to Enantioselective Photochemical Reactions

“…Consequently,a lternative Lewis acids were investigated that could be chelated by the carbonyl and aryloxy oxygen atoms. The[ 6 p]p hotocyclization of substrates 18 [29,30] was relatively unexplored at the time and was therefore chosen as am odel reaction for enantioselective photochemistry starting from a-substituted enones 18 (Scheme 12). [31] As expected, ac onsiderable bathochromic shift was observed with EtAlCl 2 as the Lewis acid.…”