RESUMO
A comparative study, ultrasound (US) versus microwave (MW) versus conventional thermal heating (TH), for synthesis of isoindolo-1,2-diazine is described. The reaction pathway is fast, efficient and straight applicable, involving a Huisgen [3+2] dipolar cycloaddition of cycloimmonium ylides to 1,4-naphthoquinone. A feasible reaction mechanism for the obtaining of the fully aromatized tetra- and penta- cyclic isoindolo-1,2-diazine is presented. Under US irradiation the yields are much higher (sometimes substantially, by almost double), the reaction time decreases substantially, the reaction conditions are milder. The use of a generator with a higher nominal power induces higher yields and short reaction times. Overall the use of US it proved to be more efficient than MW or TH. A feasible explication for US efficiency is presented.
Assuntos
Compostos Heterocíclicos/síntese química , Isoindóis/síntese química , Micro-Ondas , Ultrassom , Compostos Heterocíclicos/química , Isoindóis/química , Estrutura Molecular , TemperaturaRESUMO
A fast, general, environmentally friendly and facile method for preparation of five- and six-membered ring diazaheterocylic salts under microwave irradiation is presented. The N-alkylation reactions of imidazole, pyrimidine, pyridazine and phthalazine have been studied. The microwaves remarkably accelerated these N-alkylations, the reaction times decreased dramatically, the reaction conditions were milder, the consumed energy decreased considerably and the amount of solvents used was reduced substantially. Consequently, the microwave assisted alkylation of N-containing heterocycles could be considered eco-friendly. In some cases, under MW irradiation the yields are also higher. A comparative study of microwave vs. classical conditions (liquid solvents) has been done. Twelve new diazaheterocylic salts of potential practical interest were obtained.
Assuntos
Compostos Heterocíclicos , Micro-Ondas , Sais , Técnicas de Química Combinatória , Compostos Heterocíclicos/síntese química , Compostos Heterocíclicos/química , Imidazóis/química , Estrutura Molecular , Ftalazinas/química , Piridazinas/química , Pirimidinas/química , Sais/síntese química , Sais/química , Solventes/química , Tiamina/análogos & derivadosRESUMO
A new, fast, efficient and general method for preparation of steroid analogous of anticipated biological activity under ultrasound irradiation and classical heating is reported. The reaction pathway involves two steps: quaternization of phthalazine heterocycle followed by a 3+2 dipolar cycloaddition of cycloimmonium ylides to dienophiles. Under ultrasound the reaction time decreases substantially, the yields are higher, the reaction conditions are milder. A comparative study ultrasound verses classical heating has been done.
