A new, efficient and easy route for the preparation of a series of 2-alkyl(aryl) substituted 4-oxo-4H-pyrido-[1,2-a]pyrimidines, where alkyl = CH 3 ; aryl = C 6 H 5 , 4-FC 6 H 4 , 4-ClC 6 H 4 , 4-BrC 6 H 4 , 4-CH 3 C 6 H 4 , 4-OCH 3 -C 6 H 4 , 4-NO 2 C 6 H 4 in 45 -80 % yield from the reaction of β-alkoxyvinyl trichloromethyl ketones with 2-aminopyridine under mild conditions, is then reported.J. Heterocyclic Chem., 43, 229 (2006).In the last years, the introduction of a trifluoro-or trichloromethyl group into an acyclic or cyclic compound have widely been studied and reviewed [1,2]. Consequently, these new organic structures can bring about remarkable changes in their physical, chemical and biological properties.Recently, we have also reported an addition/elimination sequence leading to trifluoroacetyl and trichloroacetyl acyclic enamines from the reaction of o-phenylenediamine [3], o-aminophenol [4], 1-naphthylamine [5] and S,Sdimethylsulfoximide [6] with 4-alkyl(aryl)-1,1,1-trihalo-4-alkoxyalken-2-ones. The acyclic enaminones, derived from o-phenylenediamine and o-aminophenol, were submitted to in vitro anti-tumor screens. It was observed that the trichloromethylated compounds exhibited a superior activity if compared to trifluoromethylated analog compounds. The best activity was obtained when the structure was derived from o-aminophenol and it presents a trichloroacetyl-and a p-bromophenyl substituent bound at the carbon-2 and -1, respectively [4].β-Alkoxyvinyl trichloromethyl ketones 1 proved also to be useful building blocks for the synthesis of five-, six-, and seven-, member trichloromethylated heterocycles [2] due to the fact that one of the best methods to introduce a trichloromethyl group into heterocycles is based on the trichloromethylated building block approach. This approach relies on the trichloroacetylation of enol ethers or acetals to give, in one step and good yields, the above cited ketones 1. On the other hand, the classical haloform reaction in which the trichloromethyl substituent is a leaving group is well developed [7] and systematic studies, involving the usefulness of the leaving group ability of the trichloromethyl in many synthetic transformations, were reported [2,[8][9][10][11][12][13][14]. However, just a few references from the literature report the use of the trichloromethyl substituent as a good leaving group in heterocyclic synthesis [15]. Furthermore, the synthetic strategy involving the ketones 1 and 2-aminopyridine was never applied in attempt to obtain regiospecificaly 2-alkyl(aryl)substituted 4H-pyrido[1,2-a]pyrimidin-4-ones under relative mild conditions.Although some researches, up to 1951, considered that the heterocycle obtained from the reaction of 2-aminopyridine with ethyl acetoacetate was 4-methyl-2H-pyrido[1,2-a]pyrimidin-2-one, Antaki and Petrow [16] showed (in 1951), that the product was, in fact, the 2-methyl-4-keto isomer. To prove this hypothesis, 2-methyl-4H-pyrido[1,2-a]pyrimidin-4-one was obtained from the reaction of 2-bromopyridine with ethyl β-amin...

The synthesis of a novel series of the intermediates N2(N3)‐[1‐alkyl(aryl/heteroaryl)‐3‐oxo‐4,4,4‐trifluoroalk‐1‐en‐1‐yl]‐2‐aminopyridines [F3CC(O)CHCR1(2NHC5H3N)] and 2,3‐diaminopyridines [F3CC(O)CHCR1(2‐NH2‐3‐NHC5H3N)], where R1 = H, Me, C6H5, 4‐FC6H4, 4‐CIC6H4, 4‐BrC6H4, 4‐CH3C6H4, 4‐OCH3C6H4, 4,4′‐biphenyl, 1‐naphthyl, 2‐thienyl, 2‐furyl, is reported. The corresponding series of 2‐aryl(heteroaryl)‐4‐trifluoromethyl‐3H‐pyrido[2,3‐b][1,4]diazepin‐4‐ols obtained from intramolecular cyclization reaction of the respective trifluoroacetyl enamines or from the direct cyclocondensation reaction of 4‐methoxy‐1,1,1‐trifluoroalk‐3‐en‐2‐ones with 2,3‐diaminopyridine, under mild conditions, is also reported.

Fused pyrimidine derivatives R 0515 New Efficient Approach for the Synthesis of 2-Alkyl(aryl) Substituted 4H-Pyrido[1,2-a]pyrimidin-4-ones. -The cyclocondensation reaction proceeds regiospecifically to the title compounds (III), but fails in the case of (IV). -(BONACORSO*, H. G.; RIGHI, F. J.; RODRIGUES, I. R.; CECHINEL, C. A.; COSTA, M. B.; WASTOWSKI, A. D.; MARTINS, M. A. P.; ZANATTA, N.; J. Heterocycl. Chem. 43 (2006) 1, 229-233; Nucl. Quim. Heterociclos, Univ. Fed.

Multi-membered N-heterocycles R 0690 Preparation of New 2-Amino-(VI) and 2,3-Diamino-pyridine Trifluoroacetyl Enamine Derivatives (III) and Their Application to the Synthesis of Trifluoromethyl-Containing 3H-Pyrido[2,3-b][1,4]diazepinols (IV). -(BONACORSO*, H. G.; LOUREGA, R. V.; RIGHI, F. J.; DEON, E. D.; ZANATTA, N.; MARTINS, M. A. P.; J.