Síntese de compostos heterocíclicos nitrogenados via reações de ciclização promovidas por espécies eletrofílicas de organocalcogênios: síntese de derivados de azaespiros e pirroloquinolinas

Abstract

In the present work, a synthetic route was developed for the preparation of 3- (organochalcogenyl)-azaespiro. The methodology developed involves an ipso cyclization reaction of arylpropynyl amides 1 in the presence of phenyl selenium bromine 2. After a study in search of the best optimization condition, it was found that the use of 1.3 equivalents of the electrophilic species, in nitromethane at 90 ° C for 22 hours guaranteed the best conversion of the starting materials into the desired product. The developed condition was applied to a range of arylpropynyl amides 1 and electrophilic species of organochalcogens 2, leading to the formation of 22 new compounds derived from 3- (organochalcogenyl)-azaspiro. The realization of mechanistic studies indicated that the reaction occurs through an electrophilic cyclization route, and it is possible to observe that halogen (bromine) acts as the base and leads to the aromatization of the system. In a second step, a synthetic protocol was developed for the preparation of 5- (organochalcogenyl)pyrrole[1,2-a] quinolines. The methodology developed involves a cyclization reaction of the type 6-endo-dig of 1- (4-methyl-2- (phenylethynyl) phenyl) -1H-pyrrole and derivatives 7, in the presence of diorganoyl dichalcogenides 8 and ferric chloride. The study of the best reaction condition demonstrated that, in the presence of 1.1 equivalents of diorganoyl dicalcogenide 8, ferric chloride (2.0 equiv.), in dichloromethane at room temperature for 30 minutes, there is a conversion of the starting material in the desired product in a good yield. The developed methodology was applied to different substrates and, in the end, 22 new compounds derived from 5-(organochalcogenyl)pyrrole[1,2-a]quinolines were obtained. It should be noted that, at the end of both developed protocols, some of the compounds obtained were selected and they were subjected to Suzuki-type cross-coupling reactions, leading to the obtaining of 2 new compounds in a yield range of (68-73%).