Studies on tellurium-containing heterocycles. Part 20. Reactions of 2-benzoselenopyrylium salts and 2-benzotelluropyrylium salts with nucleophiles: formation of 1-functionalized 1H-isoselenochromenes and 1H-isotellurochromenes.
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The reactions of the 2-benzoselenopyrylium (1A) and 2-benzotelluropyrylium cations (1B) with a variety of nucleophiles have been investigated. LiAlH(4), sodium alkoxide (NaOMe, NaOi-Pr and NaOt-Bu), diethylamine, n-butylamine and acetone reacted with 1 to give the 1H-isochromenes (2) and the corresponding 1-substituted products (4-9) under mild conditions in almost good to high yields. The 1-alkyl(phenyl)isoselenochromenes (10-13) and 1-benzylisochromenes (18A, 18B), which were produced by the reaction of the salts 1 with Grignard reagents, were converted to the corresponding 1,3-disubstituted 2-benzopyrylium salts (14-17, 19) by treatment with triphenylcarbenium tetrafluoroborate (Ph(3)C(+) BF(4)(-)), respectively. The 1-benzylselenopyrylium salts (19A) and 1-benzyltelluropyrylium salts (19B) exist in the solvent as an equilibrium mixture of the salts (19) and the corresponding (Z)-benzylidene compounds (20). (+info)
Highly regioselective palladium-catalyzed annulation reactions of heteroatom-substituted allenes for synthesis of condensed heterocycles.
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We have developed a highly regioselective synthesis of heterocycles via palladium-catalyzed annulation reaction of heteroatom-substituted allenes. Various aryl halides were reacted and one regioisomer was observed exclusively in all reactions. In addition, subsequent functionalizations of annulated products were carried out using alkyl metal reagents, and the introduction of alkyl moieties was accomplished. (+info)
Experimental and theoretical studies on the functionalization reactions of 4-benzoyl-1,5-diphenyl-1H-pyrazole-3-carboxylic acid and acid chloride with 2,3-diaminopyridine.
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The 1H-pyrazole-3-carboxylic acid 2 was converted in good yield (69%) into the corresponding 1H-pyrazole-3-carboxamide 5 via reaction of the acid chloride 3 with 2,3- diaminopyridine (4). A different product, the 3H-imidazo[4,5-b] pyridine derivative 6, was formed from the reaction of 3 with 4 and base in benzene for 5 hours. The structures of the synthesized compounds were determined spectroscopically. The mechanism of the reaction between 3 and 4 was examined theoretically. (+info)
Endogenous and synthetic agonists of GPR119 differ in signalling pathways and their effects on insulin secretion in MIN6c4 insulinoma cells.
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