Acylimines of hexafluoroacetone and methyl trifluoropyruvate in cyclocondensation with 2-aminopyridines

Abstract

Cyclocondensation of acylimines of hexafluoroacetone and methyl trifluoropyruvate with 2 aminopyridines afforded earlier unknown fluoro containing 2H pyrido[1,2 a] [1,3,5]triazines.It is known that acylimines of hexafluoroacetone (HFA) and methyl trifluoropyruvate (MTFP) in cyclo condensation with bisnucleophiles act as 1,3 and 1,2 bis electrophilic reagents 1,2 and serve as promising starting material for the synthesis of various fluoro containing heterocycles. For instance, dehydration of adducts of HFA perfluoroacylimines and perfluorocarboxamides with oleum gives 1,3,5 oxadiazines; 3 reactions of HFA and MTFP benzoylimines with 6 aminouracil give 4 pyrimido and pyrrolopyrimidines, respectively; dehydration of the adduct of HFA ethoxycarbonylimine and 2 aminopyrimi dine with PCl 5 gives pyridotriazine. 5 In the present work, we studied the cyclocondensation of HFA and MTFP acylimines with 2 aminopyridines, which yields earlier unknown fluoro containing 2H pyrido[1,2 a][1,3,5]tri azines. The compounds obtained can be regarded as po tential biologically active substances. Pyridotriazines are known to exhibit high fungicidal, 6 antimitotic, 7 and cyto static activities. 8,9The transformations studied follow a two step scheme: (1) addition of 2 aminopyridine to the C=N bond of imines 1 and 2 to give adducts 4 and 5 and (2) dehyd ration of adducts 4 and 5 with PCl 5 to 2H pyri do[1,2 a][1,3,5]triazines 6 and 7. In the case of 2 amino 4 methylpyridine (3a), intermediate adducts 4a and 5a (Scheme 1) were isolated in the individual state and char acterized.The cyclocondensation of 2 aminopyridines 3b-f with acylimines of HFA (1b-f) and MTFP (2b-e) (equimolar amounts of the reagents were mixed in ben zene at 20 °C; after the exothermic reaction was com pleted, PCl 5 was added and the reaction mixture was refluxed until the precipitate dissolved; intermediate ad ducts were not isolated) afforded 2,2 bis(trifluoromethyl) 2H pyrido[1,2 a][1,3,5]triazines 6b-h and methyl 2 tri fluoromethyl 2H pyrido[1,2 a] [1,3,5]triazine 2 carboxy lates 7b-f in 55 to 74% yields (Scheme 2).Pyridotriazines 6a-h and 7a-f are crystalline solids; their compositions and structures were proved by elemen tal analysis, NMR spectroscopy, and chemical transfor mations. Their 19 F NMR spectra show characteristic sig nals at δ -1.0 to 1.0 for geminal trifluoromethyl groups (6a-h) and a trifluoromethyl group (7a-f).The reaction of ester 7a with hydrazine hydrate in MeOH gave 2H pyrido[1,2 a][1,3,5]triazine 2 carbo hydrazide 8 (Scheme 3).Thus, the annelation of substituted 2 aminopyridi nes with HFA and MTFP acylimines proceeds via the Scheme 1 Х = CF 3 (1a, 4a, 6a); C(O) OMe (2a, 5a, 7a)

Acylimines of hexafluoroacetone in cyclocondensation with C,N-binucleophiles

“…The 1 H and 19 F NMR spectra were recorded on a Bruker DXP 200 spectrometer in DMSO d 6 . The melting points were determined in a glass capillary.…”

“…Acylimines of hexafluoroacetone serve as synthons for the synthesis of various heterocyclic compounds contain ing geminal trifluoromethyl groups and are used as heterodienes and dienophiles in cycloaddition with ni triles, 1,2 derivatives of trivalent phosphorus acids, 3 and cyclopentadiene 4 as well as 1,3 bielectrophilic reagents in cyclocondensation with 1,3 binucleophiles 5, 6 to give oxadiazines, oxazaphospholenes, azanorbornenes, and dihydrotriazines, respectively. In the present study, we examined the synthetic possibilities of acylimines of hexafluoroacetone 1 as 1,3 bielectrophilic reagents for the preparation of 1,4 dihydropyrimidines by cyclo condensation with 1,3 C,N binucleophiles.…”

Esters of 2-aryl-2-isocyanato-3,3,3-trifluoropropionic acid in cyclocondensation with amines

“…The derivatives of esters of trifluoropyruvic acid, like N-substituted imines of trifluoropyruvates, are successfully used in the synthesis of fluorinated heterocyclic compounds [1][2][3][4][5]. The most promising in this respect is the use of these reagents as 1,3-bielectrophiles in the reactions of cyclocondensation [6][7][8][9][10]. The goal of the present study is the synthesis of new bielectrophiles based on ethyl fluoropyruvate, that is, the esters of 2-aryl-2-isocyanato-3,3,3-trifluoropropionic acid, and investigation of their behavior in the reactions of cyclocondensation.…”

Arenesulfonylimines of methyl trifluoropyruvate in the cyclocondensation reactions with 1,3-C,N-and-N,N-binucleophiles

“…[4][5][6][7][8][9] In the present work, new data on the synthetic potentiali ties of arenesulfonylimines of MTFP 1 in the prepara tion of fluorine containing N arenesulfonylated hetero cycles by the cyclocondensation of compounds 1 with 1,3 C,N and N,N binucleophiles are presented. It should be noted that earlier, sulfonylimines of polyfluoro ketones were used in the synthesis of heterocycles with fluorine containing substituents (the aza Diels-Alder reaction), 10 as well as of biologically active fluorine con taining aminophosphonates, the serine hydrolase in hibitors.…”