Photodecarboxylative Cyclizations of ω-Phthalimido-para-phenoxy Carboxylates

摘要

The chemistry of electronically-excited phthalimides is dictated by electron and/or hydrogen transfer reactions.1'2 The photochemistry of phthalimides has been intensively studied, and numerous synthetically useful transformations with high chemical and quantum yields have been developed.3 Among the synthetic applications, intra- and intermole-cular photodecarboxylation (PDC) of co-phthalimidoalkyl carboxylates has been developed by Griesbeck and coworkers as a versatile pathway to medium- and large-ring heterocycles.4 Model reactions were further realized on macro- and micro-scales.5 We recently described PDC cyclizations of co-phthalimidoalkynoates to produce macrocyclic alkynes with ring-sizes up to 17.6 In recent study, we expanded the portfolio of this reaction and investigated the photochemistry of related aryl-linked phthalimides in Scheme 1. Based on these approaches, we demonstrated that co-phthalimido-ortho/meta-phenoxy carboxylates undergo efficient PDC cyclizations.7'8 While the yields of co-phthali-mido-ortho-phenoxy carboxylates steadily decreased with increasing chain-length and the maximum yield of the 6- membered product was obtained in 75%, the yields of meta-phenoxy carboxylates steadily increased with increasing chain-length and the extended 16-membered product was subsequently obtained in 48% yield.