Selective C-3 lithiation of 2,3-dibromo- and 2,3-diiodo-1-methylindoles

Reaction of 2,3-dibromo-1-methylindole with tert-butyllithium at −78 °C followed by treatment with tropylium ion gave 2-bromo-3-cycloheptatrienyl-1-methylindole in a moderate yield, indicating that 2-bromo-3-lithio-1-methylindole would be involved as an intermediate instead of 3-bromo-2-lithio-1-methylindole. The structure of 2-bromo-3-cycloheptatrienyl-1-methylindole was unequivocally determined by a single X-ray analysis. 2,3-Diiodo-1-methylindole also gave a 3-lithio derivative exclusively.     

The chemical behavior of 2-methylene-2,3-dihydro-3-furanones

Diphenylketene undergoes regioselective thermal [2+2]-cycloaddition to the heterocyclic C(3)=O carbonyl group of 5-aryl-2-methoxycarbonylmethylene-2,3-dihydrofuran-3-ones and 5-phenyl-2,3-dihydrofuran-2,3-dione to give the corresponding 3-diphenylmethylene derivatives of 2,3-dihydrofuran.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 331–334, February, 1995.     

Novel and Expedient Regioselective Synthesis of 2-Imino-3-methyl-2,3-dihydrothiazoles

Cyclization of α-tosyloxyacetophenones 1 and N-methylthiourea 2 in acidic medium affords a novel and expedient method to synthesize 2-imino-3-methyl-2,3-dihydrothiazoles 3 with excellent level of regiocontrol.     

Unexpected observations during the total synthesis of calothrixin B–sodium methoxide as a source of hydride

During the total synthesis of calothrixin B, various novel and unexpected results were noticed such as cleavage of C–N bond in imine using sodium cyanoborohydride, sodium methoxide as a hydride source for reduction, deformylation in the presence of bromine, and deacylation using ceric ammonium nitrate (CAN). A detailed mechanism has been proposed for the unexpected results and a few of them are generalized. Temperature dependent NMR studies have been carried out for confirmation of the structure of one of the intermediates in the synthetic sequence.     

Selective reductive cleavage of 2,3-epoxybromides by the InCl3-NaBH4 reagent system

A combination of sodium borohydride and a catalytic amount of indium(III) chloride in acetonitrile reduces 2,3-epoxybromides to the corresponding allylic alcohols in good yields involving reduction of the bromo moiety followed by selective C-O bond cleavage through a radical process. Several aromatic, cyclic and open-chain bromoepoxides successfully participated in this reaction.     

Reaction of 3-Benzoyl-2,3-dibromopropionic Acid with Substituted ortho-Phenylenediamines

3-Benzoyl-2,3-dibromopropionic acid reacts with 4-substituted o-phenylenediamines to give 3-aryl-2-carboxymethylene-1,2-dihydroquinoxalines.     

Synthesis, Structure, and Chemical Properties of N-Substituted 2(3)-Imino-2,3-dihydrofuran-3(2)-ones. (Review)

Published data on the synthesis, structure, and chemical properties of N-substituted 2(3)-imino-2,3-dihydrofuran-3(2)-ones to 2002 are reviewed     

The investigation in 2,3'-biquinoline series 26.* Regioselective nitration of 1'-alkyl-1',4'-dihydro-2,3'-biquinolin-4'-ones and 1'-alkyl-1',2'-dihydro-2,3'-biquinolin-2'-ones

The nitration of 1'-alkyl-1',4'-dihydro-2,3'-biquinolin-4'-ones and 1'-alkyl-1',2'-dihydro-2,3'-biquinolin-2'-ones has been investigated. It was shown that the regioselectivity of nitration of the first depends on the acidity of the medium and the order of adding reactants. In strongly acidic medium 1'-alkyl-5,6'-dinitro-1',4'-dihydro-2,3'-biquinolin-4'-ones or mixtures of them with 1'-alkyl-5-nitro-1',4'-dihydro-2,3'-biquinolin-4'-ones are formed. In less acidic media 1'-alkyl-6'-nitro-1',4'-dihydro-2,3'-biquinolin-4'-ones and then 1'-alkyl-6,6'-dinitro-1',4'-dihydro-2,3'-biquinolin-4'-ones are formed. Nitration of 1'-alkyl-1',2'-dihydro-2,3'-biquinolin-2'-ones leads to 1'-alkyl-6'-nitro-1',2'-dihydro-2,3'-biquinolin-2'-one and then 1'-alkyl-6,6',8'-trinitro-1',2'-dihydro-2,3'-biquinolin-2'-one. *For Communication 25 see [1]. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 578-585, April, 2009.     

Nucleophilic reactions of l-methyl-2-methoxy-2-phenyl-3-oxo-2,3-dihydroindole

The title compound (1) was prepared via methylene blue (MB)-sensitized photooxy-genation of l-methyl-2-phenylindole (2d) in methanol. Acid-catalyzed nucleophilic substitution of 1 with nucleophiles gave 1,2,2-trisubstituted 3-oxo-2,3-dihydroindoles (3–6). Reduction of 1 with lithium aluminum hydride, followed by acidic workup yielded 4d and 2d, whereas the same reduction reaction of 1, followed by neutral workup gave l-methyl-2-phenyl-3-hydroxy-2,3-dihydroindole (15), together with 3. The reaction pathways of nucleophilic substitution and reduction of 1 were discussed.     

Regioselective reduction of 3-substituted N-acylpyrazinium salts toward the synthesis of 1,2-dihydropyrazines

The regioselective reduction of 3-substituted N-acylpyrazinium salts with n-Bu(3)SnH has been developed for the synthesis of 3-substituted 1,2-dihydropyrazines in yields of 56-94%. Substitution of the pyrazinium salts with electron-donating groups favors the formation of the 1,2-isomers as a result of their better stability over the 1,6-isomers. Under mild acidic conditions, 3-methoxy substituted 1,2-dihydropyrazine was easily hydrolyzed in excellent yield to Δ(5)-2-oxopiperazine.     

Investigations in the Field of 2,3'-Biquinolyl. 14. Reaction of Dihydro Derivatives of 2,3'-Biquinolyl with Bromine and Iodine

Methods were developed for the synthesis of 6'-bromo- and 6',8'-dibromo-2,3'-biquinolyls and 3',4'-dibromo- and 3',4',6'-tribromo-1'-ethoxycarbonyl-1',2',3',4'-tetrahydro-2,3'-biquinolyls on the basis of the bromination of the dihydro derivatives of 2,3'-biquinolyl. It was shown that the reaction of 1'-alkyl-1',4'-dihydro-2,3'-biquinolyls with bromine and iodine leads to 1'-alkyl-1',2'-dihydro-2,3'-biquinolyl-2'-ones.     

Synthesis and crystal structure of ethyl 1-benzyl-2-hydroxy-5-methyl-3-oxo-2-phenacyl-2,3-dihydropyrrole-4-carboxylate

Reaction of 5-phenyl-2,3-dihydro-2,3-furandione with ethyl 3-benzylamino-2-butenoate, resulting in ethyl 1-benzyl-2-hydroxy-5-methyl-3-oxo-2-phenacyl-2,3-dihydropyrrole-4-carboxylate and benzylamide ofN-benzoylpyruvic acid, was studied. The structure of the pyrrole derivative was confirmed by X-ray analysis.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1552–1555, August, 1995.     

Structural Determination of the [4+2] Dimer of 2,3-Dimethylene-2,3-Dihydrothiophene from Deuterium Labeling Study

2,3-Dimethylene-2,3-dihydrothiophene (1a), prepared by the flash vacuum pyrolysis of 3-methyl-2-thienylmethyl benzoate (7a), rapidly dimerizes to form a [4 + 2] dimer 6. The structure of the [4+2] dimer 6 was confirmed by comparing its NMR spectrum with that of the [4 + 2] dimers from 2-dideuteriomethylene-3-methylene-2,3-dihydrothiophene (1b) and 2-methylene-3-dideuteriomethylene-2,3-dihydrothiophene (1c).     

Interaction of 5-Aryl-2,3-dihydrofuran-2,3-diones with Functionally Substituted Hydrazides and Diaminoglyoxal Diphenylhydrazone

The reaction of 5-aryl-2,3-dihydrofuran-2,3-diones with cyanoacetylhydrazide, o-(hydrazinocarbonyl)phenylthiourea, and the diphenylhydrazone of diaminoglyoxal leads to the synthesis of the corresponding N-cyanoacetylhydrazides of aroylpyruvic acids, 2-(N-aroylpyruvoylhydrazinocarbonyl)-phenylthioureas, and 5,6-bis(phenylhydrazono)-3-aroylmethylenepiperazin-2-ones. The results of the primary investigation of the biological activity of N-cyanoacetylhydrazides of aroylpyruvic acids are given.     

Interaction of 1-Benzyl-4-benzoyl-5-phenyl-2,3-dihydro-2,3-pyrroledione with Ketene Diethylacetal: Synthesis and Crystal and Molecular Structure of 1-Benzyl-4-benzoyl-3-hydroxy-5-phenyl-5-ethoxycarbonylmethyl-2,5-dihydro-2-pyrrolone

1-Benzyl-4-benzoyl-5-phenyl-2,3-dihydro-2,3-pyrroledione reacts with ketene diethylacetal, forming 1-benzyl-4-benzoyl-3-hydroxy-5-phenyl-5-ethoxycarbonylmethyl-2,5-dihydro-2-pyrrolone, whose crystal and molecular structure was studied by XRD.     

The mechanism of unexpected reduction of dimethyl pyridine-2,3-dicarboxylate to l,2,3,4-tetrahydrofuro[3,4-b]- pyridin-5(7H)-one with sodium borohydride

An unexpected reduction of dimethyl pyridine-2,3-dicarboxylate to l,2,3,4-tetrahydrofuro[3,4-b]pyridin-5(7H)-one with sodium borohydride in ethanol and tetrahydrofuran,respectively,is described,a hypothetic mechanism for the unusual reductive product is proposed.     

Chemistry of 2-methylene-2,3-dihydro-3-furanones

[3+2]-Cycloaddition of 2-methoxycarbonylmethylene-5-phenyl-2,3-dihydro-3-furanone to acetone azine has been studied. This results in a monospirocycloadduct,viz., 9,9-dimethyl-6-methoxycarbonyl-2-phenyl-1-oxa-7,8-diazaspiro[4.4]nona-2,6-dien-4-one. Its structure has been confirmed by X-ray diffraction analysis.For the previous communication see Ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 306–308, February, 1994.