Том 52, № 9 (2016)

The mechanism of nucleophilic addition of ethane-1,2-dithiol to 4-hydroxy-4-methylpent-2-ynenitrile has been studied at the DFT B3LYP/6-311++G(d,p) level of theory. The base-catalyzed reaction involves nucleophilic attack by deprotonated ethane-1,2-dithiol on the ß-carbon atom of the nitrile with formation of intermediate Z-vinylic carbanion which undergoes intramolecular cyclization with closure of 1,3-dithiolane ring. Further transformation of 2-[2-(2-hydroxypropan-2-yl)-1,3-dithiolan-2-yl]acetonitrile to 6,6-dimethyl-7-oxo-1,4-dithiaspiro[4.4]nonan-8-imine has also been studied.

Various carbonitriles were synthesized by reaction of the corresponding carboxylic acids with acetonitrile in carbon tetrachloride in the presence of VO(acac)₂ and Mo(CO)₆ in 6 h at 150–170°C.

Procedures have been developed for the synthesis of 2-formylbenzofuran-5,6-dicarbonitriles, 5,6-dicyanobenzofuran-2-carboxylic acids, and formyldibenzo[b,d]furan-2,3-dicarbonitriles by modification of 2-(2-aminovinyl)benzofuran-5,6-dicarbonitriles with sodium periodate or Vilsmeier reagent.

Methods have been developed for the synthesis of new heterocyclic systems, spiro[chromene-4,3′- indoles] and spiro[indole-3,4′-quinolines] by the base-catalyzed domino reaction of isatins with 5,5-dimethylcyclohexane- 1,3-dione (or 5,5-dimethyl-3-anilinocyclohex-2-en-1-one) and ethyl cyanoacetate.

Coupling of 3-alkyl-4-aryl-1H-pyrazole-5-diazonium chlorides with methylene-active methyl phenacyl sulfones afforded new pyrazolo[5,1-c][1,2,4]triazine derivatives via cyclization of the corresponding intermediate 1-aryl-2-(hetarylhydrazinylidene)-2-(methanesulfonyl)ethanones. The reactivity of the methanesulfonyl group on C³ of pyrazolo[5,1-c][1,2,4]triazines toward some nucleophiles was studied.

The molecular and crystal structures of the ionic associate formed by 2-aminobenzimidazolium cation solvated by one dimethyl sulfoxide molecule and 3,3′-(phenylmethylene)bis(4-hydroxy-2H-chromen-2- one) anion were determined by X-ray analysis. This associate was isolated in the acid-catalyzed three-component reaction of 4-hydroxy-2H-chromen-2-one with benzimidazol-2-amine and benzaldehyde together with regioisomeric dihydrochromenopyrimidobenzimidazolones resulting from the classical Biginelli condensation. The steric and electronic structures of the cation and anion were calculated at the B3LYP/6-311++G(d,p) level of theory in combination with NBO analysis. Factors stabilizing the ion pair and crystal field effects on the stability of the associate and its constituents were considered. The formation of 3-[(2,4-dioxo-3H-chromen-3-yl)(phenyl)methyl]-2-oxo-2H-chromen-4-olate anion in the one-pot reaction was shown to be irreversible.

“Push–pull” enamines of the 1,2,3,4-tetrahydroisoquinoline series, 2-(3,3-dimethyl-1,2,3,4-tetrahydroisoquinolin- 1-ylidene)acetamides, reacted as 1,3-binucleophiles with ninhydrin to form tricyclic tetrahydroindeno[1,2-b]pyrrole system. The nucleophilic centers in the enamines were the amide NH₂ group and ß-carbon atom of the enamine fragment. The reaction of ninhydrin with 2-[2,2-dimethyl-2,3-dihydrobenzo[f]-isoquinolin-1(4H)-ylidene]-1-(pyrrolidin-1-yl)ethanone involved only addition to the ß-carbon atom of the enamine fragment. The different reaction directions were rationalized by steric effect of two methyl groups in position 3 of the isoquinoline ring. The Knoevenagel condensation product was obtained by the reaction of ninhydrin with drotaverine (base). The structure of the 1,3-addition product, (3aS,8bS,Z)-{2,2-dimethyl-2,3- dihydrobenzo[f]isoquinolin-4(1H)-ylidene}-3a,8b-dihydroxy-1,3,3a,8b-tetrahydroindeno[1,2-b]pyrrole-2,4-dione, was confirmed by X-ray analysis.

6-Imino-1,3-dimethyl-5-(pyrrolidin-2-ylidene)-5,6-dihydropyrimidine-2,4(1H,3H)-dione reacted with substituted benzoyl chlorides in the presence of triethylamine to give the corresponding 10-(R-benzoyl)-2,4-dimethyl-6-(R-phenyl)-8,9-dihydropyrimido[5,4-e]pyrrolo[1,2-c]pyrimidine-1,3(2H,4H)-diones. Analogous reaction with thionyl chloride afforded 2,4-dimethyl-9,10-dihydro-6λ⁴-pyrimido[5,4-d]pyrrolo[1,2-b][1,2,6]-thiadiazine-1,3,6(2H,4H,8H)-trione.