Síntese e transformações de Diels-Alder de 2-estirilcromonas: síntese de flavonas contendo unidades do ripo pirimidina

Abstract

Na primeira parte desta dissertação reporta-se a síntese de 2-estirilcromonas, 5-hidroxi-2-estirilcromonas e benziloxi-2-estirilcromonas; e de precursores de dienos do tipo o-quinodimetanos, 2,2-dióxido de 1,3-di-hidrobenzo[c]tiofeno, 2,2-dióxido de 4,7-dimetoxi-1,3-di-hidrobenzo[c]tiofeno e 6,6-dióxido de 2- metil-4-metoxi-5,7-di-hidrotieno[3,4-d]pirimidina. Na segunda parte desta dissertação reportam-se os estudos de reacções de Diels-Alder de 2-estirilcromonas com dienos gerados “in-situ”, por extrusão térmica de dióxido de enxofre, a partir de sulfonas, ambos atrás referidos. Estes resultados permitiram analisar a reactividade das 2-estirilcromonas como dienófilos em reacções de Diels-Alder em função dos seus substitutintes e estabelecer novos métodos de síntese de 2-[2-(3-aril-1,2,3,4-tetrahidronaftil)] cromonas, 2-[2-(3-aril-1,2,3,4-tetra-hidronaftil)]-5-hidroxicromonas, 2-{2-[3-(3,4-dibenziloxifenil)-5,8-dimetoxi-1,2,3,4-tetrahidronaftil]} benziloxicromonas, 2-[6-(7-fenil-2-metil-4-metoxi-5,6,7,8-tetrahidroquinazolil)] cromonas, 2-[7-(6-fenil-2-metil-4-metoxi-5,6,7,8-tetrahidroquinazolil)] cromonas, 2-[6-(7-fenil-2-metil-4-metoxi-5,6,7,8-tetrahidroquinazolil)]- 5-hidroxicromonas e de 2-[7-(6-fenil-2-metil-4-metoxi-5,6,7,8- tetra-hidroquinazolil)]-5-hidroxicromonas. Na terceira parte reportam-se os estudos de reacções de desidrogenação dos cicloaductos sintetizados com vista à obtenção das 2-[2-(3-arilnaftil)]cromonas, 2-[2-(3-arilnaftil)]-5-hidroxicromonas, 2-{2-[3-(3,4-dibenziloxifenil)-5,8- dimetoxinaftil]}benziloxicromonas, 2-[6-(7-fenil-2-metil-4- metoxiquinazolil)]cromonas, 2-[7-(6-fenil-2-metil-4-metoxiquinazolil)]cromonas, 2-[6-(7-fenil-2-metil-4-metoxiquinazolil)]-5-hidroxicromonas e de 2-[7-(6-fenil-2- metil-4-metoxiquinazolil)]-5-hidroxicromonas. Na caracterização estrutural dos compostos sintetizados recorreu-se a técnicas analíticas actuais, especialmente a estudos vários de espectroscopia de ressonância magnética nuclear (RMN), os quais incluíram sobretudo o estudo de espectros de RMN de 1H, de 13C e estudos bidimensionais de correlação espectroscópica homo e heteronuclear e de efeito nuclear de Overhauser.

In the first part of this dissertation the synthesis of 2-styrylchromones, 5- hydroxy-2-styrylchromones and benzyloxy-2-styrylchromones; and precursors of o-quinodimethane-type dienes, 2,2-dioxide of 1,3-dihydrobenzo[c]thiofene, 2,2-dioxide of 4,7-dimethoxy-1,3-dihydrobenzo[c]thiofene and 6,6-dioxide of 2- methyl-4-methoxy-5,7-dihydrotiene[3,4-d]pyrimidine is reported. In the second part we report the study on Diels-Alder reactions of 2- styrylchromones with dienes generated “in situ”, by extrusion of sulphur dioxide, from sulphones, both referred above. These results allow us to discuss the reactivity of 2-styrylchromones as dienophiles in Diels-Alder reactions according their substitutents and establishing new synthetic methods for 2-[2- (3-aryl-1,2,3,4-tetrahydronaphthyl)]-chromones, 2-[2-(3-aryl-1,2,3,4- tetrahydronaphthyl)]-5-hydroxychromones, 2-{2-[3-(3,4-dibenzyloxyphenyl)-5,8- dimethoxy-1,2,3,4-tetrahydronaphthyl]}-benzyloxychromones, 2-[6-(7-phenyl-2- methyl-4-methoxy-5,6,7,8-tetrahydroquinazolyl)]-chromones, 2-[7-(6-phenyl-2- methyl-4-methoxy-5,6,7,8-tetrahydroquinazolyl)]-chromones, 2-[6-(7-phenyl-2- methyl-4-methoxy-5,6,7,8-tetrahydroquinazolyl)]-5-hydroxychromones and 2-[7- (6-phenyl-2-methyl-4-methoxy-5,6,7,8-tetrahydroquinazolyl)]-5- hydroxychromones. In the third part we report the study on dehydrogenation reactions of the synthesised cicloadducts to obtain the 2-[2-(3-arylnaphthyl)]chromones, 2-[2- (3-arylnaphthyl)]-5-hydroxychromones, 2-{2-[3-(3,4-dibenzyloxyphenyl)-5,8- dimethoxynaphthyl]}benzyloxychromones, 2-[6-(7-phenyl-2-methyl-4- methoxyquinazolyl)]chromones, 2-[7-(6-phenyl-2-methyl-4-methoxyquinazolyl)] chromones, 2-[6-(7-phenyl-2-methyl-4-methoxyquinazolyl)]-5- hydroxychromones and 2-[7-(6-phenyl-2-methyl-4-methoxyquinazolyl)]-5- hydroxychromones. All synthesised compounds were characterised using modern analytical techniques, with special emphasis on exhaustive nuclear magnetic resonance (NMR) spectroscopic studies. The NMR methods used include 1H, 13C, two dimensional homonuclear and heteronuclear correlated spectroscopy and nuclear Overhauser effect experiments.