Reactions of 2-alkoxy-5-trifluoroacetyl-3,4-dihydro-2H-pyrans with substituted ethylamines and arylamines

Conselho Nacional de Desenvolvimento Científico e TecnológicoThis work presents the synthesis of two novel series of 1-alkyl(aryl)-2-amino- 5-trifluoroacetyl-1,2,3,4-tetrahydropyridine (6, 8), obtained from the reaction of 2- alkoxy-5-trifluoroacetyl-3,4-dihydro-2H-pyrans (alkoxy = OMe (3), EtO (4)) with primary ethylamines, with general formula R1CH2CH2NH2, where R1 = 2-MeO-Ph (5a), 4-MeO-Ph (5b), 3,4-OMe-Ph (5c), 4-F-Ph (5d), 2-Cl-Ph (5e), 3-Cl-Ph (5f), 4-Cl- Ph (5g), 2,4-Cl-Ph (5h), 4-OH-Ph (5i) , 1-(2-cycloexenyl) (5j), 1-(2-N-morpholil) (5k), 1-(2-N-diethylamino) (5l) and 2-(1H-indole-3-yl) (5m), and primary arylamines, of general formula NH2-Ar were Ar = 4-F-Ph (7a), 2-OMe-Ph (7b), 3-OMe-Ph (7c), 2- OH-5-Me-Ph (7d). The cyclic enones 3,4 were obtained by acylation of 2-alkoxy-3,4- dihydro-2H-pyrans with trifluoroacetic anhydride, in chloroform, under catalysis of pyridine (Py), according to the literature. The tetrahydropyridines (6), derived from ethylamines 5a-m was obtained in high yields (90-98%) using methanol or ethanol as solvent at room temperature (r.t.) for a period of 24 hours. For the reaction of cyclic enones 3 and 4 with amines 5i, 5l and 5m the addition of an excess of amines and equimolar amount of triethylamine were need. The second series of tetrahydropyridines (8) was obtained from the reaction of primary arylamines (7a-d) with enones 3 and 4, using methanol or ethanol as solvent at room temperature. The correspondent tetrahydropyridines (8a-d) were obtained with yields ranging from 86 to 98%.Este trabalho apresenta a síntese de duas séries inéditas de 1-alquil(aril)-2- amino-5-trifluoracetil-1,2,3,4-tetraidropiridinas (6,8), obtidas a partir da reação de 2- alcóxi-5-trifluoracetil-3,4-diidro-2H-piranos (alcóxi = MeO (3), EtO (4)) com etilaminas primárias, de fórmula geral R1CH2CH2NH2, onde R1 = 2-MeO-Ph (5a), 4- MeO-Ph (5b), 3,4-OMe-Ph (5c), 4-F-Ph (5d), 2-Cl-Ph (5e), 3-Cl-Ph (5f), 4-Cl-Ph (5g), 2,4-Cl-Ph (5h), 4-OH-Ph (5i), 1-(2-cicloexenil) (5j), 1-(2-N-morfolil) (5k), 1-(2-Ndietilamino) (5l) e 2-(1H-indol-3-il) (5m), e arilaminas primárias, de fórmula geral NH2-Ar sendo, Ar: 4-F-Ph (7a), 2-OMe-Ph (7b), 3-OMe-Ph (7c), 2-OH-4-Me-Ph (7d). As enonas cíclicas 3, 4 foram obtidas a partir da acilação do 2-alcóxi-3,4-diidro-2Hpiranos com anidrido trifluoracético, em clorofórmio sob catálise de piridina (Py), de acordo com a literatura. As tetraidropiridinas (6), derivadas de etilaminas 5a-m, foram obtidas em ótimos rendimentos (90 - 98%) empregando metanol ou etanol como solvente, à temperatura ambiente (t.a.) por um período de 24 horas. Para a reação das enonas cíclicas 3 e 4 com as aminas 5i, 5l e 5m houve a necessidade de adição de excesso de amina e de quantidade equimolar de trietilamina. A segunda série de tetraidropiridinas (8) foi obtida a partir da reação das arilaminas primárias (7a-d) com as enonas 3 e 4, utilizando metanol ou etanol como solventes à temperatura ambiente. As tetraidropiridinas correspondentes (8a-d) foram obtidas com rendimentos que variaram de 86 a 98%