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Part-IISynthesis of Pyrimidinesexpected 4-chlorothienopyrimidine, instead the unchanged 4-aminopyrimidine wasrecovered. 60H 2 NClNCl dry HClNXdioxaneClNSSNIVIIIThis one-pot formation of 4-chloropyrimidines is indeed novel, especially, in view of thefact that 4-chloropyrimidines are normally prepared through multistep synthesis,involving the preparation of the corresponding 4-oxopyrimidine, followed by itschlorination with POCl 3 . The formation of 4-chloropyrimidines presumably proceedsthrough the transient o-cyanoamidine intermediates, 32 especially in view of thedemonstrated isolability and also the cyclization of acyclic analogs of o-cyanoamidines,namely the N-(cyanovinyl)amidines 33 to 4-chloropyrimidines 34 in the presence ofhydrogen chloride under essentially the same condition. 63,64OClONOONNH 2dry HClR 2 N N R 1HO33BrR 2 N N R 1H32dry HBrONR 2 N N R 1H34R 1 = C 6 H 5 , 4-CH 3 C 6 H 4 , 2-CH 3 C 6 H 4 , 4-ClC 6 H 4 ,4-BrC 6 H 4 , 2-CH 3 OC 6 H 4R 2 = H, CH 3 , C 6 H 5On these lines, a plausible mechanism has been proposed 29,63,64 for the formation ofcondensed functionalised 4-halopyrimidines in these reactions under the influence of dryHCl or HBr gas.It appears reasonable to assume that under the reaction conditions employed, the CNgroups of both, the substrate, o-aminonitrile and the nitrile are activated by protonation orby the formation of hydrogen halide adducts. The initial condensation between the twocomponents or their activated forms can be expected to result in the formation of the258