Aplicação de organocatalisadores de selênio como miméticos da enzima metiltransferase: benzilação de cianeto de sódio em água

• Ano de defesa: 2020
• Autor(a) principal: Nayara Silva Martins
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; Brasil; ICEX - INSTITUTO DE CIÊNCIAS EXATAS; Programa de Pós-Graduação em Química; UFMG
• Palavras-chave em Português: Reação em água; Nitrilas; Seleneto; Catálise; Sal de organocalcôgenio; Reaction in water; Nitriles; Organochalcogen salt; Catalysis; Selenide; Química orgânica; Enzimas - Análise; Solventes; Química ambiental; Selênio
• Link de acesso: http://hdl.handle.net/1843/35772

The approach is, in a simple way, a mimic to the activity of the Methyltransferase enzymes, which catalyze the transfer of a methyl group of the co-factor S-adenosyl-L-methionine (SAM) to nucleophilic substrates. Selenonium salts, generated in situ in the reaction medium, catalyze the transfer of benzyl groups to nucleophiles such as cyanide, the focus of this work - and consist of alternatives to the use of conventional alkylating agents. A highlight of the work is the use of water, an innocuous and inexpensive solvent, as the reaction solvent; and the formation of nitriles, compounds normally synthesized by processes that require high temperatures and large amounts of reagents. For this, several reaction parameters were studied, such as: the most suitable solvent, the amount and structure of the selenide, the amount of cyanide, among others. Once the reaction was optimized, benzyl nitriles and α-ketonitriles, with electron donation or withdrawing groups, were synthesized with reasonable to good yields, from the precursor halides. As a reaction condition, the use of an unknown selenide, in catalytic quantity (10 mol%), in aqueous medium and with only 2 equivalents of cyanide salt stands out. The escalation of the reaction was feasible, with the conversion of 69% of 6.0 mmol of benzyl bromide. Therefore, in this context and in an efficient way, this research introduces a versatile catalytic route that moves towards to meet the principles of Green Chemistry.