A catalytic system consisting of KI, 18-crown-6, and TBHP for arylsulfonylation of activated alkenes with sulfonylhydrazides as sulfonyl precursor is described. This protocol provides a practical and environmentally benign method for the construction of sulfonated oxindoles in water.

A practical and environmentally friendly strategy for generating alkoxycarbonyl radicals from readily available carbazates under metal-free conditions has been developed. In the presence of tetrabutylammonium iodide and tert-butyl hydroperoxide, 2-isocyanobiphenyls smoothly underwent radical alkoxycarbonylation with carbazates to afford phenanthridine-6-carboxylates.

An efficient metal-free oxidative arylsulfonylation of α,β-unsaturated imides with sulfonylhydrazides leading to isoquinoline-1,3(2H,4H)-dione derivatives has been developed. The procedure involves the generation of sulfonyl radicals via cleavage of the S-N bond of sulfonylhydrazides with sulfonylation and C-H functionalization. The protocol uses the economical and environmentally friendly TBAI-TBHP catalytic system, and the corresponding isoquinoline-1,3(2H,4H)-diones with various functional groups were obtained in moderate to good yields.

A metal-free method for the synthesis of imidazo[1,2-a]pyridines via double C-N oxidative coupling of aminopyridines with nitroolefins using TBAI as the catalyst and TBHP as oxidation agent has been developed.The imidazo[1,2-a]pyridines are an important class of heterocycles which widely exist in medicinal chemistry 1 and material science. 2 Traditional approaches for the formation of imidazo[1,2-a]pyridines rely on condensation reaction of 2-aminopyridines with α-halocarbonyl compounds. 3 Recently, the direct transition-metal-catalyzed oxidative coupling of unfunctionalized starting materials, including ketones, 4 alkynes, 5 nitroolefins, 6 β-keto esters 7 with 2-aminopyridines has attracted much attention. In particular, Huang demonstrated CuBr-catalyzed synthesis of imidazo[1,2-a]pyridine by mild oxidative double C-N coupling of nitroolefins with 2-aminopyridines using air as oxidative agent. 8 In addition, an alternative metal-free method has also been developed. Han and co-workers reported TBAI-catalyzed synthesis of imidazo[1,2-a]pyridine though tandem oxidative C-N coupling/condensation of 2-aminopyridines with β-keto esters and 1,3-diones using tert-butyl hydroperoxide (TBHP) as the oxidant. 9 However, there is still no published report on metal-free double C-N coupling protocol for the construction of imidazo[1,2-a]pyridines. As a part of our continuing research on the TBAI-catalyzed transformation, 10 we herein report the first metal-free, TBAIcatalyzed oxidative coupling of 2-aminopyridines with nitroolefins, representing a new method for the construction of imidazo[1,2-a]pyridines. We commenced our reaction with pyridin-2

The reaction works well with differently substituted indoles but only methyl‐ and benzyl protected substrates can be employed.