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High stereoselectivity on low temperature Diels-Alder reactions |
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| Authors: | da Silva Filho Luiz Carlos Lacerda Júnior Valdemar Constantino Mauricio Gomes da Silva Gil Valdo José Invernize Paulo Roberto |
| Affiliation: | Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeir?o Preto, Universidade de S?o Paulo, Av, Bandeirantes 3900, 14040-901 - Ribeir?o Preto - SP, Brazil. lcsilva@aluno.ffclrp.usp.br |
| Abstract: | We have found that some of the usually poor dienophiles (2-cycloenones) can undergo Diels-Alder reaction at -78 degrees C with unusually high stereoselectivity in the presence of niobium pentachloride as a Lewis acid catalyst. A remarkable difference in reaction rates for unsubstituted and alpha- or beta-methyl substituted 2-cycloenones was also observed. |
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