• R K Shah

      Articles written in Journal of Chemical Sciences

    • Reaction of acetylenic esters with 1,8-diaminonaphthalene, 1,8-dihydroxynaphthalene and 8-hydroxy-1,2,3,4-tetrahydroquinoline

      M D Nair K Nagarajan J A Desai Y S Kulkarni R K Shah

      More Details Abstract Fulltext PDF

      Addition of 1,8-diaminonaphthalene1 to dimethylacetylene dicarboxylate (DMAD) leads to the perimidine4a and the naphthodiazepine3a. A similar reaction with the diethyl ester (DEAD) gave rise to3b and4b. The latter product has been incorrectly formulated as naphthodiazepine2b in the literature. 1,8-Dihydroxynaphthalene8 and DMAD gives rise to the naphthodioxane9, which is hydrolysed to the diacid11. 8-Hydroxy-1,2,3,4-tetrahydroquinoline (14) and acetylenic esters form pyridobenzoxazines15, which exist as equilibrium mixture of15 and16 in solution. The ethyl ester is hydrogenated to the dihydroderivative18b.1H and more particularly13C NMR spectra are used to assign structures to various products.

    • Condensed heterotricycles: Pyrido(1,2,3-de)(1,4)benzoxazines, pyrido(1,2,3-ef)(1,5)benzoxazepines and pyrido(1,2,3-fg)(1,6) benzoxazocines

      K Nagarajan A Nagana Goud V Ranga Rao R K Shah S J Shenoy

      More Details Abstract Fulltext PDF

      Cyclization of N-(2-haloacyl)-8-hydroxy-l,2,3,4-tetrahydroqumolines47 and9 with alkali affords pyridobenzoxazinones2124 and26 respectively and of the 4-chlorobutyramide13 with NaH, the benzoxazocinone31. Exposure of 3-chloropropionamide12 to NaH affords acrylamide15, benzoxazepinone28 or methyl benzoxazinone22 or mixtures thereof under various conditions.28 undergoes rapid base-catalysed ring contraction to22. NaH-catalysed ring closure of acrylamide15 affords mixtures of22 and28, while from the crotonamides16 and17, the methylbenzoxazepinones29 and30 are obtained preponderantly, the former amide yielding only traces of the ethyl benzoxazinone23.29 shows no propensity for ring contraction to give23. The cinnamoyl derivatives18,19 and20 are cyclized to benzyl benzoxazinones24,27 and25, respectively. The intermediacy of the phenyl benzoxazepinone39 in the formation of24 has been established by deuteration studies. Benzylidene benzoxazinone41 is obtained from dibromocinnamamide14 and propiolamide40. Dichloracetamides8 and10 undergo interesting ring closure to compounds4554 upon treatment with amines. The course of electrophilic reactions of the lactams depends upon the ring size.

  • Journal of Chemical Sciences | News

© 2023-2024 Indian Academy of Sciences, Bengaluru.