High stereoselectivity on low temperature Diels-Alder reactions.
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.
Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av, Bandeirantes 3900, 14040-901 - Ribeirão Preto - SP, Brazil. lcsilva@aluno.ffclrp.usp.br
Luiz Carlos
LC
da Silva Filho
Valdemar
V
Lacerda Júnior
Mauricio Gomes
MG
Constantino
Gil Valdo José
GV
da Silva
Paulo Roberto
PR
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