RESUMO
Applications of the cascade cyclocarbopalladation reaction followed by Suzuki-Miyaura coupling reactions of the readily available aryl-substituted propargylic aryl ethers with arylboronic acid and potassium trans-ß-styryltrifluoroborate accomplish a new versatile entry in the synthesis of benzofuran derivatives. Notably, a new approach to the challenging synthesis of C3 functionalized 2-unsubstituted benzofurans has been developed by a cyclocarbopalladation/cross-coupling/aromatization process.
Assuntos
Benzofuranos/síntese química , Compostos de Boro/química , Hidrocarbonetos Bromados/química , Paládio/química , Alcinos/química , Benzofuranos/química , Catálise , Ciclização , Éteres/química , Estrutura Molecular , Compostos Organometálicos/químicaRESUMO
The scope and the generality of gold versus silver catalyzed intramolecular hydroarylation reactions of 3-[(3-arylprop-2-ynyl)oxy]benzene derivatives in terms of rings substitution were investigated. Only products deriving from 6-endo cyclization were exclusively formed. The features of substituents had a considerable effect on the reaction outcome in the presence of silver catalysis, whereas gold catalysis revealed a unique blend of reactivity and selectivity and represented the only choice for the intramolecular hydroarylation reaction of the starting substrates bearing electron deficient arenes.
Assuntos
Derivados de Benzeno/química , Benzopiranos/síntese química , Técnicas de Química Sintética/métodos , Ouro/química , Prata/química , Benzopiranos/química , Catálise , Ciclização , Estrutura MolecularRESUMO
The problem of constructing diastereoselectively the C/D ring system of stemarane diterpenes from a bicyclo[2.2.2]octane intermediate was solved resulting in very simple synthesis of (+)-13-stemarene 1. The obtaining of the latter represents also a formal synthesis of (+)-18-deoxystemarin 2. In the key step, the epimeric mixture 10, dissolved in toluene, was converted by the action of TsOH into (+)-stemar-13-en-15-one 28.