Enantiopure 1-phosphanorbornadiene-2-carboxaldehydes

The reaction of phenylpropargyl aldehyde diethyl acetal with 1-phenyl-3,4-dimethylphosphole at 140°C or 1,2,5-triphenylphosphole at 170°C leads, after deprotection, to the corresponding 1-phosphanorbornadiene-2-carboxaldehydes 3 and 4 in 88 and 45% yields, respectively. The resolution of 3 and 4 was carried out by chromatography or fractional crystallization of the acetals derived from (S,S)-1,2-diphenylethane-1,2-diol. The absolute configurations were established by X-ray analysis of one of these acetals or of a 2-bromomethyl derivative.     

Synthesis of 1-Substituted Pyrrole-3-carboxaldehydes

The Vilsmeier-Haack formylation is the route most frequently employed for the introduction of a formyl group into the 2 or 3 position of a pyrrole ring.^2,3 Factors affecting the extent of substitution in the 2 and 3 positions in N-substituted pyrroles under Vilsmeier-Haack conditions have been investigated and the product distribution appears mainly to be the result of steric interactions.^4,5 Although it is relatively simple to introduce a formyl residue into the 2-position of a pyrrole nucleus, considerable molecular manipulation must normally be undertaken to prepare pyrrole-3-carboxaldehydes which do not bear substituents in the 2 and 5 positions of the pyrrole ring.⁶ An alternative method is the generation of isomeric mixtures of pyrrole-2-carboxaldehyde and pyrrole-3-carboxaldehyde by the acid mediated rearrangement of t h e corresponding pyrrole-2-carboxaldehydes.     

Synthesis of 3-acyl-1-alkyl-2-alkylseleno-1-cyclobutene using alkyneselenolate

The reaction of lithium alkyneselenolate with alpha,beta-unsaturated ketone and then alkyl or acyl halide afforded 3-acyl-1-alkyl-2-alkylseleno-1-cyclobutene. The structure of the cyclobutene was elucidated by IR, MS, (1)H, (13)C, and (77)Se NMR, COSY, HMQC, and HMBC data and X-ray analysis.     

Synthesis of 1-alkyl-2-nitroimidazole-5-carboxaldehydes

We report the preparation of 1-methyl- and 1-ethyl-2-nitroimidazole-5-carboxaldehydes (Ia,b). For Ia three different routes of synthesis are described, which appear of general value for preparing 1-alkyl substituted 2-nitroimidazole-5-carboxaldehydes.     

Bromination of 3-acyl-2-aminoindoles

Unlike 3-acylindoles, 3-acyl-2-aminoindoles display high selectivity on being electrophilically attacked in the benzene ring, and are substituted at the 6-position. At the same time, an unco-subsitution of the acyl group takes place (to the greatest extent — the formyl group). Direct bromination of 3-acyl- and 3-cyano-2-aminoindoles provides the 6-bromo- and 6,4-dibromo-2-aminoindoles and their derivatives.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 486–490, April, 1990.     

Research on 2-acyl-3-aminobenzofurans

It is demonstrated that, depending on the position of the acetyl substituent in the furan ring of benzofuran, the Schmidt rearrangement leads to benzofuran-2-carboxylic acid methylamide or to 3-acetamidobenzofuran derivatives.See [1] for communication II.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1040–1042, August, 1977.     

Preparation of Ethyl 5-Iodo-1H-indole- 2-carboxylate

Abstract

A facile, two step procedure for the preparation of ethyl 5-iodo-1H-indole-2-carboxylate (1) from commercially available ethyl 1H-indole-2-carboxylate is described herein, employing a regioselective C3, C5-bisiodination followed by zinc-mediated C3-dehalogenation.     

新型5-取代吲哚-3-甲酰胺化合物的合成

以5-取代吲哚为原料,经维尔斯迈尔-哈克反应制得5-取代吲哚-3-甲醛(2a~2e); 2a~2e在DMF催化下,与盐酸羟胺反应制得5-取代吲哚-3-甲腈（3a~3e）; 3a~3e在H₂O₂和NaOH溶液中水解合成了5-取代吲哚-3-甲酰胺（4a~4e, 4b~4e为新化合物）,产率62.0%~75.0%,其结构经¹H NMR, ¹³C NMR和ESI-MS表征。     

Reaction of 2-acyl-3-aminobenzofurans with hydrazines

While 2-acetyl and 2-benzoyl-3-aminobenzofurans did not react with hydrazine, monomethyl- and N,N-dimethylhydrazine to give the related hydrazones, their 3-N-(p-toluenesulfonyl) derivatives afforded them smoothly in good yields. Depending upon reaction conditions, products arising from hydrazone cyclization to benzofuropyrazoles and/or from furan ring cleavage at the C2 O bond to give 5-(2-hydroxyphenyl)pyrazoles were also formed. The formation of these products depends upon hydrazones configuration and is discussed. Only (E)-isomers appear to undergo furan ring opening. In acidic media at room temprature either the hydrazones or the monomethylhydrazones gave the same related α-azines. Microanalyses, ir, uv, ¹H-nmr and ms spectra are in agreement with the proposed structures.     

Spatial structure of 3-acyl-2-methylindole oximes

It has been established on the basis of the results of ¹H and ¹³C NMR, UV, and IR spectroscopy that 3-acyl-2-methylindole oximes each exist in the form of a mixture of two isomers with a predominance of syn-s-trans form. The proportion of the anti form rises (to 25–35%) with an increase in the volume of the alkyl radical in the oxime grouping.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 65–68, January, 1984.     

A novel NHC-catalyzed transformation of 2H-chromene-3-carboxaldehydes to 3-methyl-2H-chromen-2-ones

An unexpected transformation of 2H-chromene-3-carboxaldehydes to coumarin derivatives, mediated by NHC, is reported.     

Reaction of 1-acyl-2-phenylacetylenes with thiosemicarbazide

Conclusions The reaction of 1-acyl-2-phenylacetylenes with thiosemicarbazide in methanol at 60C gives 2-amino-7-hydroxy-6,7-dihydro-1,3,4-thiadiazepines which, upon heating in -vacuum fragment with the formation of 3,5-disubstituted pyrazoles.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 216–218, January, 1987.     

Chemoselective protection of heteroaromatic aldehydes as imidazolidine derivatives : Preparation of 5-substituted furan- and thiophene-2-carboxaldehydes via metallo-imidazolidine intermediates

Furan-, thiophene- and $\text{N}$-methylpyrrole-2-carboxaldehydes may be transformed into the corresponding $\text{N}$,$\text{N}$'-dimethylimidazolidines in a reaction not requiring acid catalysis. The resulting furan and thiophene (but not $\text{N}$-methylpyrrole) derivatives may be metallated in high yields [predominantly at the 5 (α-) positions of the heteroaromatic rings] and the carboxaldehyde functionality regenerated under very mild conditions. Treatment of the aldehydoketone 2-acetyl-5-formylthiophene with $\text{N}$,$\text{N}$'-dimethylethylenediamine gives $\text{only}$ the product of reaction at the aldehyde function thus establishing this methodology as a potentially valuable method for the protection of an aldehyde in the presence of a ketone.     

Preparation of 1,2,5-thiadiazole-3-carboxaldehydes

1,2,5-Thiadiazole-3-carboxaldehydes 1a-c were prepared by the acid-catalyzed decomposition of 3-azido-methyl-1,2,5-thiadiazoles 2a-c in 68-83% yields, respectively. Pyrolysis of 2a and 2b afforded the imidazoles 4a and 4b in low yields. NBS -bromination of 1a and 1b gave the corresponding carboxylic acids 10a and 10b via acid bromides 9. Azides 2a and 2b gave the s-triazines 8a and 8b on treatment with NBS.