Chemistry of Heterocyclic Compounds

IR and PMR spectroscopy and chemical methods have been used to establish the structures of stereoisomeric 1-(3-phenylprop-2-ynyl)-2-methyldecahydroquinol-4-ones and the corresponding acetylenic alcohols.

Các tính chất quang phổ huỳnh quang và quang hóa của các muối perchlorate 1-naphthyl-2,4-di- và 2,4,6-triphenylpyridinium đã được nghiên cứu trong dung dịch ở nhiệt độ 293 và 77 °K. Sự chuyển dịch Stokes bất thường lớn của huỳnh quang là do sự thay đổi adiabatic trong cấu trúc của các phân tử do sự quay của các nhóm thế C- hoặc N-aryl. Huỳnh quang nhìn thấy được xuất hiện từ sự chuyển giao năng lượng T-T nội phân tử đến gốc N-naphthyl. Các cation 1-naphthyl-2,4-diphenylpyridinium có khả năng photocyclization với sự hình thành các hợp chất dẫn xuất huỳnh quang mạnh của benzo[b hoặc c]pyrldo[1,2-f]phenanthridinium, được tách ra với hiệu suất cao trong quá trình quang phân.

The classical method for obtaining 2,5-dimethylpyrazine by cyclization of amino-acetone has been improved by use of ammonium persulfate in place of mercuric chloride in the stage of catalytic oxidation of 2,5-dimethyldihydropyrazine. Catalytic vapor phase oxidation of 2,5-dimethylpyrazine gave 5-methylpyrazine-2-aldehyde and pyrazine-2,5-dialdehyde.

The complete series of 2-thienyl(2′-furyl)- and 2-thienyl[2′-(4′,5′-dihydrofuryl)]silanes have been synthesized, and the influence of the character and number of substituents on the chemical shifts in the1H,13C, and29Si spectra has been investigated.

A method is proposed for the synthesis of 2-methyl-3-carbethoxypyrylium salts by the acid condensation of ethoxymethyleneacetoacetic ester with alkyl aryl, heterocyclic, and cyclic ketones or resorcinol. 2-Methyl-3-carbethoxy-6-phenylpyrylium perchlorate was condensed with benzaldehyde, and the product was subjected to acid hydrolysis and decarboxylation to 2-methyl-6-phenylpyrylium perchlorate to confirm the structure of the synthesized salts.

Phenylhydrazine reacted regioselectively with 6-substituted 4-pyrone-2-carboxylic acids (or esters) in protic and aprotic solvents, leading to phenylhydrazones of 3-(3-R-1-phenylpyrazol-5-yl)- or 3-(5-R-1-phenylpyrazol-3-yl)pyruvic acids (or esters), respectively. 6-Di(tri)fluoromethylcomanic acids (or esters) reacted analogously, forming the corresponding phenylhydrazones with RF group in the side chain. The obtained phenylhydrazones underwent Fischer reaction under acidic conditions, forming the respective 3-(N-phenylpyrazolyl)indoles. In contrast to comanic acid and its ester, the reactions of 2-substituted 4-pyrones occurred non-selectively and gave mixtures of regioisomeric pyrazoles with phenylhydrazone group in the side chain or 3-(N-phenylpyrazolyl)indoles. A mechanism was proposed to explain the effect of solvent on the course of reaction.

A new method of synthesizing 1-alkoxysilatranes is described. It is based on transesterification of lower tetraalkoxysilanes with an equimolar mixture of triethanolamine and appropriate alcohol. The method is used to prepare 15 compounds of this type in 50–90% yields. Of these only one, R = = C2H5, was previously known. Their solubilities in various solvents are found. Molecular weight determinations show them to be monomeric.

For the first time, 1-amino-3-alkylbenzimidazolinethiones were obtained by heating 1-amino-3-alkylbenzimidazolium iodides with sulfur in the presence of triethylamine. They were converted to 1-amino-3-alkyl-2-(methylthio)benzimidazolium salts, which, during reaction with CH-acid onions, gave the corresponding 1-amino-3-alkyl-2-methylenebenzimidazoline derivatives. Under conditions of alkaline or acid catalysis, the latter derivatives cyclized to 2-amino- or 2-hydroxy derivatives of pyrazolo[1,5-a]benzimidazole.

1-(α-Alkoxyethyl)- and 1-(α-phenoxyethyl)benzimidazole-2-thiones were obtained in the reaction of 1-vinylbenzimidazole-2-thione with alcohols and phenol in the presence of gaseous hydrogen chloride. It was established that partial hydrolysis of the 1-(α-alkoxyethyl)benzimidazole-2-thiones to benzimidazole-2-thione with subsequent alkylation with excess alcohol at the exocyclic sulfur atom occurs under the conditions of the investigated reaction. A convenient method for the alkylation of thiones was proposed, and a number of 2-alkylthiobenzimidazoles were synthesized.