Assinalação estereoquímica de produtos e descrição de mecanismos para reações de acoplamento entre α,α-diclorocetonas e compostos carbonílicos promovidas por brometo de índio(I)

• Ano de defesa: 2007
• Autor(a) principal: Chagas, Rafael Pavão das
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Santa Maria; BR; Química; UFSM; Programa de Pós-Graduação em Química
• Palavras-chave em Português: Brometo de índio(I); Enolato de índio; Mecanismo reacional; Equilíbrio retro-aldol; Indium(I) bromide; Indium enolate; Reaction mechanism; Retroaldol reaction.; CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA
• Link de acesso: http://repositorio.ufsm.br/handle/1/10639

This work describes our results on the use of indium(I) bromide in Organic Synthesis, namely the reaction mechanisms and stereochemical outcome. Indium enolates, generated from the reaction between indium(I) bromide and α,α-dichloroketones, react with carbonyl compounds. The primary coupling with aldehydes leads to the diastereoselective synthesis of (syn+anti)-2-chloro-3-hydroxypropan- 1-ones, which can be converted to the respective trans-epoxyketones, exclusively. The indium(III) alkoxides of the 2-chloro-3-hydroxy-propan-1-ones are transformed into their (E)-prop-2-en-1-ones derivatives upon reaction with InBr according to a sequenced reaction mechanism. The most relevant feature of these reactions is that although the primary coupling with aldehydes affords a mixture of the two diastereoisomers of the indium(III) alkoxides, both the trans-epoxyketones and the E-enones were produced with rigorous stereoselectivity. These results are understood in terms of the enolate geometry (E or Z) and the retro-aldol reaction (kinetic/thermodynamic control) relating both forms of the enolate.