Vol 54, No 1 (2018)

A one-pot procedure has been developed for the synthesis of phenylhydrazones by ozonolysis of olefins in methanol at 0°C and subsequent reduction of peroxide intermediate with excess 1: 2 mixture of phenylhydrazine hydrochloride and sodium acetate.

N-Substituted 1,4-quinone imines with an activated sterically hindered C=N bond characteristically react with nucleophiles via 1,2-addition to that bond with formation of quinolide compounds. The C=N–X bond angle in these quinone imines ranges from 130 to 145°, the upper limit being defined by their thermodynamic stability. According to the X-ray diffraction data, the real C=N–X can be smaller than 130°C, but in this case considerable deviations of the nitrogen atom and substituent attached thereto from the mean-square plane of the quinoid ring and twisting of the C=N bond are observed.

The condensation of ethyl 4-(chloromethyl)-2,6-dimethylpyridine-3-carboxylate with substituted phenols in ethanol in the presence of potassium carbonate afforded the corresponding aryl pyridin-4-ylmethyl ethers. Analogous condensation with substituted anilines gave 2-aryl-4,6-dimethyl-1,2-dihydropyrrolo[3,4-c]- pyridin-3-ones. Esters containing 1,2-azole fragments were synthesized by acylation of hydroxymethylsubstituted ethers with 5-arylisoxazole- and 4,5-dichloroisothiazole-3-carbonyl chlorides.

A modified version of the three-component Biginelli reaction of 4-hydroxy-6-methyl-2H-pyran-2-one with aromatic aldehydes in urea under conventional heating and microwave activation has been studied. Depending on the order of addition of the reactants, substituted (pyrano)chromenones, 10-amino-4a-hydroxydihydropyranochromen- 2-one, and 3-[amino(phenyl)methyl]-4-hydroxypyran-2-one were obtained.

6-Hydroxy-5-[2-(naphthalen-1-yl)ethyl]-3a,5,6,6a-tetrahydro-4H-pyrrolo[3,4-d]isoxazol-4-ones in the presence of boron trifluoride–diethyl ether complex underwent cyclization to benzo[f]isoxazolo[5′,4′: 3,4]- pyrrolo[2,1-a]isoquinoline derivatives as mixtures of two diastereoisomers. Analogous cyclization of 6-hydroxy- 5-(naphthalen-1-ylmethyl)-3a,5,6,6a-tetrahydro-4H-pyrrolo[3,4-d]isoxazol-4-ones gave benzo[de]isoxazolo[ 5′,4′: 3,4]pyrrolo[2,1-a]isoquinolines as a single diastereoisomer. The cyclization of 6-hydroxy-5-[2-(1Hindol- 3-yl)ethyl]-6,6a-dihydro-3aH-pyrrolo[3,4-d]isoxazol-4(5H)-ones catalyzed by Sn(NTf₂)₄ afforded isoxazolo[ 5′,4′: 1,2]indolizino[8,7-b]indol-4(12H)-ones in moderate yields. 6-Hydroxy-5-[2-(thiophen-2-yl)ethyl]-6,6a-dihydro-3aH-pyrrolo[3,4-d]isoxazol-4(5H)-ones were converted to 4,5,10a,10b-tetrahydroisoxazolo- [5,4-a]thieno[2,3-g]indolizin-7(7aH)-one derivatives in the presence of BF3 · Et2O or Sn(NTf₂)₄.

Betulin and diacetylbetulin, which can be regarded as sterically hindered alkenes, reacted with N-chloro-, N-bromo-, and N-iodosuccinimides to give products of allylic and vinylic substitution in quantitative overall yield. The contribution of allylic substitution increases in the series Cl < Br < I. Quantum chemical simulation of the reactions of diacetylbetulin with N-halosuccinimides showed that, regardless of the electrophile power, all reactions involve open-chain carbocationic intermediates. The direction of deprotonation of the latter with formation of allylic or vinylic substitution products is determined by preferential orientation of the vacant orbital and C–Hlg bond.

Hydroxyl-containing ionic liquids were synthesized by quaternization of 1,2-dimethyl-1H-imidazole, N-methylpyrrolidine, and pyridine with 2-chloroethanol or 6-chlorohexan-1-ol, followed by exchange of chloride ion for bis(trifluoromethanesulfonyl)azanide, and their properties were studied.

Benzimidazole reacted with diethyl vinylphosphonate to give diethyl 2-(1H-benzimidazol-1-yl)- ethylphosphonate. The addition of 2-aminobenzimidazole to vinylphosphonate involved the endocyclic nitrogen atom with formation of diethyl 2-(2-imino-2,3-dihydro-1H-benzimidazol-1-yl)ethylphosphonate.

Nucleophilic addition of imidazole to arabinogalactan propargyl ether has been accomplished for the first time in the presence of hydrogen tetrachloroaurate(III) tetrahydrate with the goal of obtaining new pharmacologically promising polysaccharides.