• V Ranga Rao

      Articles written in Journal of Chemical Sciences

    • Synthesis oftrans-N-2-aryl(heteryl)ethenamidines

      K Nagarajan P Rajagopalan B G Advani V Ranga Rao G A Bhat

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      2-Amino-2-arylethylamides1 carrying electron-donating substituents in thepara position are transformed by hot POC13 to the the title compounds2, presumably via iminochlorides 7 and imidazolium derivatives8. Amides lacking this para-substituent give rise to chloroamidines11 under these conditions.m-Methoxyphenethylamide1t and POCl3 form, besides11f, an isoquinoline derivative3. The involvement of an imidazolium compound8 in the formation of ethenamidines has been verified by the synthesis of2a from10. Reaction of amide1w with PCl5 in the cold leads to, besides the chloroamidine11c, thecis-ethenamidine12 which equilibrates with thetrans-isomer2o in hot toluene. Thienylethyl urea13 converted by hot POCl3 to the imidazoline16, while phenylpropylamide17 forms only the iminochloride18a.

    • 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

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      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.

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