1-Acetylvinyl Acrylates: New Captodative Olefins Bearing an Internal Probe for the Evaluation of the Relative Reactivity of Captodative against Electron-Deficient Double Bonds in Diels-Alder and Friedel-Crafts Reactions
نویسندگان
چکیده
As olefinas captodativas 3a e 3b derivadas dos ácidos metacrílico e trans-crotônico foram preparadas. A presença de uma segunda ligação dupla na molécula, atuando como marcador interno, permitiu-nos comparar sua reatividade relativa em reações de Diesl-Alder e Friedel-Crafts. A reatividade foi avaliada com ciclopentadieno (6) atuando como dieno em cicloadição Diels-Alder, e com furano (9) e tiofeno (10) como substratos heteroaromáticos Friedel-Crafts. Em ambos os processos, a ligação dupla da enona captodativa mostrou-se mais reativa que a do sistema acrílico. A teoria FMO considera essa quimiosseletividade como consequência da maior contribuição da enona ao orbital LUMO dessas moléculas. A pequena seletividade exo observada na cicloadição com 6 concorda com a maior estabilidade do estado de transição, de acordo com os resultados de cálculos B3LYP/6311G(d,p).
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