Catalytic Arylsulfonyl Radical Triggered 1,7-Enyne Bicyclizations

A new metal-free bicyclization reaction of 1,7-enynes anchored by α,β-conjugates with arylsulfonyl radicals generated in situ from sulfonyl hydrazides has been established using tert-butyl hydroperoxide and tetrabutylammonium iodide. The reactions occurred through sulfonylation/6-exo-dig/6-exo-trig bicyclization/in situ desulfonylation/5-exo-trig cyclization/alkyl or alkenyl migration cascade mechanism to give benzo­[j]­phenanthridines regioselectively.

本研究建立了一类无金属（metal-free）参与的双环化反应，该反应以α,β-共轭体（α,β-conjugates）锚定的1,7-烯炔（1,7-enynes）为底物，与由磺酰肼（sulfonyl hydrazides）原位生成的芳基磺酰自由基（arylsulfonyl radicals）发生反应，并以叔丁基过氧化氢（tert-butyl hydroperoxide）与四丁基碘化铵（tetrabutylammonium iodide）为反应促进剂。该反应通过磺酰化/6-exo-dig/6-exo-trig双环化/原位脱磺酰化/5-exo-trig环化/烷基或烯基迁移级联反应机理进行，可区域选择性地得到苯并[j]菲啶（benzo[j]phenanthridines）类产物。