Preparation of 4-arylquinazolines with o-(N-alkyl,N-p-tosyl)aminobenzonitriles, aryllithiums, and NIS.

The treatment of o-(N-alkyl,N-p-tosyl)aminobenzonitriles with aryllithiums, followed by the reaction with water, NIS under irradiation with a fluorescent lamp, and then tBuOK gave 2-alkyl-4-arylquinazolines or 4-arylquinazolines in good to moderate yields. The present reaction proceeds through the formation of N-iodoimines from imines with NIS, the generation of iminyl radicals, the 1,6-H shift by iminyl radicals, the cyclization via 6-exo-tet mode, and finally the elimination of p-toluenesulfinate to generate 2-alkyl-4-arylquinazolines or 4-arylquinazolines.

Correction: Preparation of 2-arylquinolines from ß-arylpropionitriles with aryllithiums and NIS through iminyl radical-mediated cyclization.

Correction for 'Preparation of 2-arylquinolines from ß-arylpropionitriles with aryllithiums and NIS through iminyl radical-mediated cyclization' by Hiroki Naruto, et al., Org. Biomol. Chem., 2019, 17, 5760-5770.

Preparation of 2-arylquinolines from ß-arylpropionitriles with aryllithiums and NIS through iminyl radical-mediated cyclization.

Treatment of ß-arylpropionitriles with aryllithiums, followed by the reaction with water and then with NIS under irradiation with a tungsten lamp gave 2-arylquinolines in good to moderate yields. The present reaction proceeds through the formation of N-iodoimines from imines with NIS, the generation of imino-nitrogen-centered radicals, and their cyclization onto the aromatic rings of the imines to form 2-aryl-3,4-dihydroquinolines. Finally, the oxidation of 2-aryl-3,4-dihydroquinolines with NIS proceeds smoothly to generate 2-arylquinolines.

Preparation of Phenanthridines from o-Cyanobiaryls via Addition of Organic Lithiums to Nitriles and Imino Radical Cyclization with Iodine.

Simple treatment of 2-cyanobiaryls with methyllithium, ethylmagnesium bromide, butyllithium, phenyllithium, p-methylphenyllithium, etc., followed by the reaction with water and then with molecular iodine at 60 °C provided efficiently 6-methyl-, 6-ethyl-, 6-butyl-, 6-phenyl, 6-( p-methylphenyl)phenanthridines, etc., in good yields, respectively. Here, imines formed through the addition of carbanion onto the nitriles reacted with molecular iodine to form N-iodoimines smoothly, and their warming treatment induced the formation of imino radicals that smoothly cyclized onto the aryl group to give 6-alkyl- and 6-arylphenanthridines.

One-pot preparation of 4-aryl-3-bromocoumarins from 4-aryl-2-propynoic acids with diaryliodonium salts, TBAB, and Na2S2O8.

Various 4-aryl-3-bromocoumarins were smoothly obtained in moderate yields in one pot by treating 3-aryl-2-propynoic acids with diaryliodonium triflates and K2CO3 in the presence of CuCl, followed by the reaction with tetrabutylammonium bromide (TBAB) and Na2S2O8. The obtained 3-bromo-4-phenylcoumarin was transformed into 4-phenylcoumarin derivatives bearing C-H, C-S, C-N, and C-C bonds at 3-position.

1,3-Iodo-amination of 2-methyl indoles via Csp2-Csp3 dual functionalization with iodine reagent.

A 1,3-iodo-amination with iodine reagent that involved the Csp2-Csp3 dual functionalization of 2-methyl indoles was developed to provide 2-aminomethyl-3-iodo-indole derivatives. The iodo-amination proceeded via a 1,4-transfer of an imide group through the formation of an indolyl(phenyl)iodonium imide using PhI(OAc)2, followed by an iodination using DIH or a double iodination of indole using excess DIH.

Preparation of 3-Iodoquinolines from N-Tosyl-2-propynylamines with Diaryliodonium Triflate and N-Iodosuccinimide.

4-Aryl and 4-alkyl substituted 3-iodoquinolines could be smoothly obtained in one pot by treating N-tosyl-2-propynylamines with diaryliodonium triflate in the presence of K3PO4 and a catalytic amount of CuCl at room temperature, followed by treatment with N-iodosuccinimide and BF3·OEt2 at 0 °C, and then NaOH in methanol solution. The product, 3-iodo-4-phenylquinoline was smoothly transformed into 4-phenylquinoline with zinc; 4-phenyl-3-toluenesulfenylquinoline with toluenethiol, K2CO3, and CuI; 4-phenyl-3-phenylethynylquinoline with the Sonogashira coupling reaction; 4-phenyl-3-styrylquinoline with the Heck coupling reaction; 3,4-diphenylquinoline with the Suzuki-Miyaura coupling reaction; 2-cyclohexyl-3-iodo-4-phenylquinoline with cyclohexanecarboxylic acid, Ag2CO3, and K2S2O8; and 3-iodo-2-(2',5'-dioxan-1'-yl)-4-phenylquinoline with benzoyl peroxide in dioxane.

Catalytic dehydrogenative dual functionalization of ethers: dealkylation-oxidation-bromination accompanied by C-O bond cleavage via aerobic oxidation of bromide.

Catalytic dehydrogenative dual functionalization (DDF) of ethers via oxidation, dealkylation, and α-bromination by the aerobic oxidation of bromide was developed to obtain the corresponding α-bromo ketones in high yields. In particular, the reaction of substituted tetrahydrofurans as cyclic ethers provided 3,3-dibromo tetrahydrofuran-2-ols in high yields selectively through the double α-bromination.

Introduction of Quinolines and Isoquinolines onto Nonactivated α-C-H Bond of Tertiary Amides through a Radical Pathway.

Treatment of quinolines and isoquinolines with benzoyl peroxide in tertiary amides, such as N,N-dimethylacetamide, N,N-dimethylpropionamide, and N-acetylpyrrolidine, etc., under irradiation with a Hg lamp in the temperature range of 35 °C to 40 °C gave C-C-bonded quinolines and isoquinolines bearing amide groups with high regioselectivity in good to moderate yields, respectively, under transition-metal-free conditions.

Preparation of Heteroaromatic (Aryl)iodonium Imides as I-N Bond-Containing Hypervalent Iodine.

Hypervalent iodine(III) compounds containing iodine-nitrogen bonds are very attractive amination reagents in organic synthesis. Heteroaromatic (aryl)iodonium imides containing a iodine-nitrogen bond and a hypervalent iodine(III) atom were prepared from heteroarenes, bis(sulfon)imides and (diacetoxyiodo)arenes under mild conditions. These compounds were stable under air and in organic solvents, and could be easily purified by precipitation. X-ray crystal structure analysis indicated that the structure of N-pivaloyl indolyl(phenyl)iodonium bis(tosyl)imides and N-pivaloyl indolyl(2-butoxyphenyl)iodonium bis(tosyl)imides was a dimer with a T-shaped geometry at the iodine atom linked to an indole group and a bis(tosyl)imide by a monomer unit. Moreover, the use of substituted iodoarenes facilitated the purification of some of the heteroaromatic (aryl)iodonium imides.

Nitroxyl-Radical-Catalyzed Oxidative Coupling of Amides with Silylated Nucleophiles through N-Halogenation.

A nitroxyl-radical-catalyzed oxidative coupling reaction between amines with an N-protecting electron-withdrawing group (EWG) and silylated nucleophiles was developed to furnish coupling products in high yields, thus opening up new frontiers in organocatalyzed reactions. This reaction proceeded through the activation of N-halogenated amides by a nitroxyl-radical catalyst, followed by carbon-carbon coupling with silylated nucleophiles. Studies of the reaction mechanism indicated that the nitroxyl radical activates N-halogenated amides, which are generated from N-EWG-protected amides and a halogenation reagent, to give the corresponding imines.

Magnesium Lewis Acid Assisted Oxidative Bromoetherification Involving Bromine Transfer from Alkyl Bromides with Aldehydes by Umpolung of Bromide.

An oxidative bromoetherification involving a bromine transfer from alkyl bromides upon reacting them with aldehydes in a Grignard reaction with a concurrent oxidation of bromide was developed to provide substituted tetrahydrofurans in high yields. This reaction, which proceeds through two types of bromine transfer, was promoted by the addition of a Brønsted acid. Mechanistic studies suggested that a magnesium Lewis acid activates hypobromate, which is generated in situ from the reaction of bromide and Oxone to improve the electrophilicity of the bromonium ion (Br(+) ) for the oxidative bromoetherification of alkenyl alcohols. Furthermore, the magnesium Lewis acid catalyzed oxidative bromoetherification of an alkenyl alcohol proceeded to provide a cyclization product in 92 % yield.

Preparation of 5-Aryl-2-Alkyltetrazoles with Aromatic Aldehydes, Alkylhydrazine, Di-tert-butyl Azodicarboxylate, and [Bis(trifluoroacetoxy)iodo]benzene.

A variety of 5-aryl-2-methyltetrazoles and 5-aryl-2-benzyltetrazoles were directly prepared in good to moderate yields by the reaction of aromatic aldehydes with methylhydrazine and benzylhydrazine, followed by treatment with di-tert-butyl azodicarboxylate and [bis(trifluoroacetoxy)iodo]benzene in a mixture of dichloromethane and 2,2,2-trifluoroethanol at room temperature. The present method is a novel one-pot preparation of 5-aryl-2-methyltetrazoles and 5-aryl-2-benzyltetrazoles through a [2N + 2N] combination under transition metal-free and mild conditions.

Direct Preparation of 3-Iodochromenes from 3-Aryl- and 3-Alkyl-2-propyn-1-ols with Diaryliodonium Salts and NIS.

On the basis of a study of the O-phenylation of 3-phenyl-2-propyn-1-ol with diphenyliodonium triflate and t-BuONa, a variety of 4-aryl-3-iodo-2H-benzopyrans were prepared in good to moderate yields in one pot from the reaction of 3-aryl-2-propyn-1-ols with diaryliodonium triflates and t-BuONa, followed by the treatment with N-iodosuccinimide and BF3·OEt2, under transition-metal-free and mild conditions. The formed 4-phenyl-3-iodo-2H-benzopyran was converted into 4-phenyl-2H-benzopyran derivatives through C-C bond formations at the 3-position by Pd-catalyzed coupling reactions and into coumarin with oxidants.

Direct Transformation of Ethylarenes into Primary Aromatic Amides with N-Bromosuccinimide and I2-Aqueous NH3.

A variety of ethylarenes were converted into the corresponding primary aromatic amides in good yields via treatment with N-bromosuccinimide in the presence of a catalytic amount of 2,2'-azobis(isobutyronitrile) in a mixture of ethyl acetate and water, acetonitrile and water, or chloroform and water, followed by reaction with molecular iodine and aq NH3 in one pot. It was found that aryl α-bromomethyl ketones and/or aryl methyl ketones were formed at the first reaction step and their iodoform-type reaction occurred at the second reaction step to provide primary aromatic amides. The present reaction is a useful and practical transition-metal-free method for the preparation of primary aromatic amides from ethylarenes.

Divergent Synthesis of α,γ-Disubstituted γ-Butyrolactones through Diastereoselective Bromolactonization with Alkali Metal Bromide: Asymmetric Total Synthesis of (+)-Dubiusamine C.

A divergent synthesis of α-substituted bromomethyl γ-lactones was developed, which involves the diastereoselective bromolactonization of α-substituted 4-pentenoic acids and 4-pentenamides via umpolung of bromide by use of alkali metal bromide and Oxone (potassium peroxymonosulfate mixture, 2KHSO5·KHSO4·K2SO4) to obtain mainly cis-products from α-substituted 4-pentenoic acids and trans-products from α-substituted 4-pentenamides, and it was found that the bromonium species generated from KBr and Oxone had higher activity than N-bromosuccinimide. Furthermore, the asymmetric total synthesis of (+)-dubiusamine C, which was isolated as a minor diastereomer from Pandanus dubius, was accomplished for the first time through the cis-selective bromolactonization of (S)-α-methyl-4-pentenoic acid in nine linear steps and 36% overall yield.

Regioselective C(sp2)-H dual functionalization of indoles using hypervalent iodine(III): bromo-amination via 1,3-migration of imides on indolyl(phenyl)iodonium imides.

A regioselective C(sp(2))-H dual functionalization of indoles, which underlies bromo-amination via the 1,3-migration of imide groups on indolyl(phenyl)iodonium imides as novel imide-combined hypervalent iodines(III), has been developed to provide 2-bis(sulfonyl)amino-3-bromo-indoles under the metal-free conditions.

Oxidative debenzylation of N-benzyl amides and O-benzyl ethers using alkali metal bromide.

The oxidative debenzylation of N-benzyl amides and O-benzyl ethers was promoted with high efficiency by a bromo radical formed through the oxidation of bromide from alkali metal bromide under mild conditions. This reaction provided the corresponding amides from N-benzyl amides and carbonyl compounds from O-benzyl ethers in high yields.

Selective oxidation of alcohols with alkali metal bromides as bromide catalysts: experimental study of the reaction mechanism.

A bromide-catalyzed oxidation of alcohols was developed which proceeded in the presence of an alkali metal bromide and an oxidant under mild conditions. The reaction involved an organic-molecule-free oxidation using KBr and Oxone and a Brønsted acid assisted oxidation using KBr and aqueous H2O2 solution to provide a broad range of carbonyl compounds in high yields. Moreover, the bromide-catalyzed oxidation of primary alcohols enabled the divergent synthesis of carboxylic acids and aldehydes under both reaction conditions in the presence of TEMPO. A possible catalytic mechanism was suggested on the basis of various mechanistic studies.

Preparation of 3,5-disubstituted pyrazoles and isoxazoles from terminal alkynes, aldehydes, hydrazines, and hydroxylamine.

The reaction of terminal alkynes with n-BuLi, and then with aldehydes, followed by the treatment with molecular iodine, and subsequently hydrazines or hydroxylamine provided the corresponding 3,5-disubstituted pyrazoles or isoxazoles in good yields with high regioselectivity, through the formations of propargyl secondary alkoxides and α-alkynyl ketones. The present reactions are one-pot preparation of 3,5-disubstituted pyrazoles from terminal alkynes, aldehydes, molecular iodine, and hydrazines, and 3,5-disubstituted isoxazoles from terminal alkynes, aldehydes, molecular iodine, and hydroxylamine.