A novel method for the synthesis of trifluoromethyl-containing 1′H-spiro[azirine-2,4′-quinolin]-2′(3′H)-ones by a CF3-radical-triggered tandem reaction of benzene-linked 1,7-enynes is described. This protocol utilizes 1-trifluoromethyl-1,2-benziodoxole as the trifluoromethylating reagent and TMSN3 as the aminating reagent. By this method, various potentially bioactive trifluoromethylated 1′H-spiro[azirine-2,4′-quinolin]-2′(3′H)-ones were facilely synthesized via a radical cascade process.

N-Alkyl enamines can be transformed into 2,4,5-trisubsituted imidazoles by reacting with (diacetoxyiodo)benzene and TMSN3 under the catalysis of a copper salt such as Cu(OAc)2. Tetrabutyl ammonium iodide was also capable of promoting the reaction. The transformation from N-alkyl enamines into 2,4,5-trisubsituted imidazoles took place in a domino azidation/intramolecular C(sp3)–H amination pattern. The present reaction provides a new efficient method for the preparation of 4-(trifluoromethyl) imidazoles.

This paper reports a new radical-based method for the synthesis of quinazolinones from α-azidyl benzamides. Under the conditions of visible light irradiation with N-bromosuccinimide (NBS), α-azidyl benzamides were transformed into the corresponding iminyl radicals via regio-selective α-hydrogen abstraction and denitrogenation; the thus formed iminyl radicals then underwent cyclization to afford the quinazolinones. The scope of this method was examined by applying it to α-azidyl benzamides of different structural features. It was found that the key cyclization step is influenced by conformational effects as well as substituent effects. As the current approach can be implemented under mild tin-free conditions by using readily accessible precursors, it has practical applicability in the synthesis of quinazolinones.

A novel vicinal sulfoximation of alkenes was achieved under mild and metal-free conditions by using readily available sulfinic acids as the sulfonating agent and tert-butyl nitrite (TBN) as the radical initiator and the oxime source. Various structurally important α-sulfonyl ketoximes can be prepared from unactivated as well as activated alkenes in high efficiency by utilizing this protocol.

A convenient and versatile oxidative intra/intermolecular oxyamination and diamination of unactivated alkenes has been developed through copper-catalyzed radical reactions of β,γ- and γ,δ-unsaturated ketoximes with electron-rich aryl and aliphatic amines. These reactions were carried out by employing di-tert-butyl peroxide (DTBP) or air as the terminal oxidant, and a series of useful nitrogen-containing 4,5-dihydroisoxazoles and cyclic nitrones were formed.Keywords: alkene; Cu; diamination; iminoxyl radicals; oxyamination

A new method was developed for the synthesis of quinoxalines. This method employs N-arylenamines and TMSN3 as the starting materials and implements two oxidative C–N bond-forming processes in a tandem pattern by using (diacetoxyiodo)benzene as the common oxidant. The present reaction conditions are mild and simple and thus are useful in practical synthesis.

The reactions of 2-azido-N-arylacrylamides with trifluoromethyl radicals and azidyl radicals were investigated by using Togni's reagent and Zhdankin's reagent as the source of these radicals. Under the catalysis of CuI, Togni's reagent was firstly converted into the trifluoromethyl radical, which then reacted with 2-azido-N-arylacrylamides to afford the corresponding α-(arylaminocarbonyl)iminyl radicals. The cyclization of the iminyl radicals delivered quinoxalin-2(1H)-one products in moderate yields. A similar reaction took place between 2-azido-N-arylacrylamides and the azidyl radical. In the latter cases, the reaction produced 3-azidomethyl and 3-cyano-subsituted quinoxalin-2(1H)-ones. This study not only helps elucidate the factors influencing the cyclization of α-(arylaminocarbonyl)iminyl radicals, but also provides a new approach towards quinoxalin-2-ones.

This paper reports a new method for the synthesis of 3-aminooxindole derivatives. Ethyl 2-(N-arylcarbamoyl)-2-iminoacetates, which can be prepared from the reaction of α-ethoxycarbonyl-α-bromo-N-phenylacetamides with sodium azide, were found to undergo Friedel–Crafts cyclization to afford 3-aminooxindoles in high yield by the catalysis of an acid such as BF3⋅OEt2. α-Aryl-α-azido-N-arylamides, on the other hand, were transformed to 3-arylaminooxindoles via a tandem 1,2-aryl migration-dinitrogenation and cyclization by the action of triflic acid. As both ethyl 2-(N-arylcarbamoyl)-2-iminoacetates and α-aryl-α-azido-N-arylamides are easily accessible, the current reactions are expected to be practically useful in the synthesis of 3-aminooxindole derivatives.

Correction for ‘Synthesis of benzo[a]carbazoles and indolo[2,3-a]carbazoles via photoinduced carbene-mediated C–H insertion reaction’ by Jidong Yang et al., RSC Adv., 2014, 4, 13704–13707.

A new synthesis of 5-hydroxy-benzo[a]carbazoles has been achieved by employing the photoinduced intramolecular C–H insertion of 2-aryl-3-(α-diazocarbonyl)indoles as the key step. This method is applicable to the synthesis of natural products 6-cyano-5-methoxy-indolo[2,3-a]carbazoles 8 and 11 and their derivatives.

A novel heterogeneous Pd catalyst was synthesized by anchoring palladium(II) onto poly(undecylenic acid-co-N-isopropylacrylamide-co-potassium 4-acryloxyoylpyridine-2,6-dicarboxylate)-coated Fe3O4 (Fe3O4@PUNP) magnetic microgel. The catalyst (Fe3O4@PUNP-Pd) was characterized by FT-IR, TEM, VSM, XRD and XPS, and the loading level of Pd in Fe3O4@PUNP-Pd catalyst was measured to be 0.330 mmol g−1 by AAS. This catalyst exhibits excellent catalytic activity for the Suzuki and Heck reactions in water. In addition, the Fe3O4@PUNP-Pd catalyst can be easily separated and recovered with an external permanent magnet, and the reuse experiment shows that it can be used consecutively six times without significant loss in catalytic activity.

This Letter presents a facile alternative synthesis of a recoverable Au(III) catalyst supported on Fe3O4@SiO2∼MPS grafted by poly(N-vinyl-2-pyrrolidone) (PVP). The solid magnetic support was prepared by anchoring 3-methacryloxypropyltrimethoxysilane (MPS) onto the Fe3O4@SiO2 surfaces followed by free radical polymerization with N-vinyl-2-pyrrolidone. Au(III) was immobilized onto the magnetic support in aqueous media to afford Au(III)/Fe3O4@SiO2∼PVP (catalyst 1). Catalyst 1 was characterized by FT-IR, TEM, VSM, TGA, XRD, and ICP-AES. The amount of Au in catalyst 1 was measured to be 0.64 wt % by ICP-AES. This newly prepared catalyst can catalyze the aromatic bromination reaction with comparable activity as homogeneous AuCl3. Moreover, the supported catalyst is easy to recover and can be used in four cycles without apparent loss of activity.

2-Electron-withdrawing-group-substituted 2-bromoanilides can be converted to the corresponding 3,3-disubstituted oxindoles with high efficiency under visible light irradiation by using fac-Ir(ppy)3 as the photoredox catalyst. This protocol is suitable for the synthesis of oxindoles with chloro and bromo atoms attached to the phenyl ring.

The reaction of ethyl α-bromocinnamates with tetrabutyl ammonium fluoride (TBAF) was influenced largely by the position of the substituent at the phenyl ring. While the substrates without an ortho substituent at the phenyl ring were transformed to the corresponding β-fluoro ethyl cinnamates under the reaction conditions, the presence of an ortho substituent only resulted in the formation of ethyl 3-phenylpropiolate derivatives. The reaction of ethyl 2-bromo-3-(4-methoxyphenyl) acrylate also failed to deliver the hydrofluorination product due to the electron-donating effect of the methoxy group.

The Cu/N-ligand/TEMPO catalytic system was first applied to the aerobic oxidative synthesis of heterocycles. As demonstrated, 2-substituted quinazolines and 4H-3,1-benzoxazines were synthesized efficiently from the one-pot reaction of aldehydes with 2-aminobenzylamines and 2-aminobenzyl alcohols, respectively, by employing CuCl/DABCO/4-HO-TEMPO as the catalysts and oxygen as the terminal oxidant.

A novel and efficient aerobic protocol for the oxidative synthesis of 2-aryl quinazolinesviabenzyl C-H bond amination by a one-pot reaction of arylmethanamines with 2-aminobenzoketones and 2-aminobenzaldehydes has been carried out using the 4-hydroxy-TEMPO radical as the catalyst, without any metals or additives.

TBAI could catalyze the direct oxidative C–N coupling of 2-aminopyridines with β-keto esters and 1,3-diones, which affords imidazo[1,2-a]pyridines as the products. The reaction was realized under metal-free conditions by using tert-butyl hydroperoxide (TBHP) as the oxidant.

Tetrabutyl ammonium fluoride (TBAF) was found to be capable of catalyzing the intramolecular hydroalkoxylation of 6-hydroxyhex-2-ynoates and 7-hydroxyhept-2-ynoates. The reaction could be used to prepare 2,5-substituted THF rings and 2,6-substituted THP rings.

The N-substituted anilines 1 react readily with phenyliodonium ylides 2 derived from 1,3-dicarbonyl compounds in the presence of a catalytic amount of BF3·Et2O, forming the C–N coupling products 3, which are precursors for the synthesis of indoles. On the basis of this result, the direct synthesis of indoles from 1 and 2 under thermal conditions and photochemical conditions was explored. The transformations could be achieved in a one-pot way under thermal conditions or in a tandem manner under photochemical conditions.

A novel vicinal sulfoximation of alkenes was achieved under mild and metal-free conditions by using readily available sulfinic acids as the sulfonating agent and tert-butyl nitrite (TBN) as the radical initiator and the oxime source. Various structurally important α-sulfonyl ketoximes can be prepared from unactivated as well as activated alkenes in high efficiency by utilizing this protocol.

The N-substituted anilines 1 react readily with phenyliodonium ylides 2 derived from 1,3-dicarbonyl compounds in the presence of a catalytic amount of BF3·Et2O, forming the C–N coupling products 3, which are precursors for the synthesis of indoles. On the basis of this result, the direct synthesis of indoles from 1 and 2 under thermal conditions and photochemical conditions was explored. The transformations could be achieved in a one-pot way under thermal conditions or in a tandem manner under photochemical conditions.

TBAI could catalyze the direct oxidative C–N coupling of 2-aminopyridines with β-keto esters and 1,3-diones, which affords imidazo[1,2-a]pyridines as the products. The reaction was realized under metal-free conditions by using tert-butyl hydroperoxide (TBHP) as the oxidant.

A novel and efficient aerobic protocol for the oxidative synthesis of 2-aryl quinazolinesviabenzyl C-H bond amination by a one-pot reaction of arylmethanamines with 2-aminobenzoketones and 2-aminobenzaldehydes has been carried out using the 4-hydroxy-TEMPO radical as the catalyst, without any metals or additives.

The reactions of 2-azido-N-arylacrylamides with trifluoromethyl radicals and azidyl radicals were investigated by using Togni's reagent and Zhdankin's reagent as the source of these radicals. Under the catalysis of CuI, Togni's reagent was firstly converted into the trifluoromethyl radical, which then reacted with 2-azido-N-arylacrylamides to afford the corresponding α-(arylaminocarbonyl)iminyl radicals. The cyclization of the iminyl radicals delivered quinoxalin-2(1H)-one products in moderate yields. A similar reaction took place between 2-azido-N-arylacrylamides and the azidyl radical. In the latter cases, the reaction produced 3-azidomethyl and 3-cyano-subsituted quinoxalin-2(1H)-ones. This study not only helps elucidate the factors influencing the cyclization of α-(arylaminocarbonyl)iminyl radicals, but also provides a new approach towards quinoxalin-2-ones.

2-Electron-withdrawing-group-substituted 2-bromoanilides can be converted to the corresponding 3,3-disubstituted oxindoles with high efficiency under visible light irradiation by using fac-Ir(ppy)3 as the photoredox catalyst. This protocol is suitable for the synthesis of oxindoles with chloro and bromo atoms attached to the phenyl ring.