The annulation reactions of N-allylbenzamides with N-sulfonylaminopyridinium salts were developed under metal-free photoinduced mild conditions. Substituent-controlled sulfonaminoarylation and sulfonaminooxylation of benzamides were realized: N-allylbenzamides lead to benzosultams, while N-(2-phenylallyl)benzamides give sulfonamidylated oxazoline derivatives. Control experiments indicated that those reactions undergo a radical pathway with arylsulfonamidyl radicals as the intermediates. The aryl C−H bond functionalization in arylsulfonamidyl was involved for the first time to give benzosultams.
A visible‐light induced radical 1,2‐aryl migration of α,α‐diarylallyl alcohols was developed under mild and metal‐free conditions. Commercially available CHCl3 and CH2Cl2 were used as tri‐ and dichloromethyl radical precursors. Structurally diverse β‐polochloromethylated ketones were obtained in good to moderate yields via neophyl‐type rearrangement. Besides, the polychloromethyl group can be easily transformed into other useful functional groups.
A visible-light-induced hydrocyclization of unactivated alkenes was developed using 3CzClIPN as the photocatalyst to generate substituted α-methyldeoxyvasicinones and α-methylmackinazolinones in moderate to good yields. An intermolecular hydrogen atom transfer with THF as the hydrogen source was involved. Mechanism studies indicated that the intramolecular addition of the in situ formed aminal radical to the unactivated alkene generated the polycyclic quinazolinone.
A visible‐light‐promoted O−H functionalization of 4‐hydroxycoumarins with α‐diazo esters was developed for the synthesis of 4‐hydroxycoumarin ethers under photocatalyst‐free conditions. Moreover, the three‐component reaction of 4‐hydroxycoumarins, α‐diazo esters and THF formed a series of 4‐hydroxycoumarin ether derivatives with alkoxyl spacers in yields up to 91%. The above mentioned solvent‐dependent carbene insertion transformations were conducted under extremely mild conditions with the tolerance of moisture and oxygen.
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