Asymmetric [4+2] Annulation Reactions Catalyzed by a Robust, Immobilized Isothiourea
A polystyrene-supported isothiourea (1a) behaves as a highly efficient organocatalyst in a variety of formal [4 + 2] cycloaddition reactions. The catalytic system has proven to be highly versatile, leading to six-membered heterocycles and spiro-heterocycles bearing an oxindole moiety in high yields...
| Autores: | , , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión borrador |
| Fecha de publicación: | 2017 |
| País: | España |
| Institución: | Varias* (Consorci de Biblioteques Universitáries de Catalunya, Centre de Serveis Científics i Acadèmics de Catalunya) |
| Repositorio: | Recercat. Dipósit de la Recerca de Catalunya |
| OAI Identifier: | oai:recercat.cat:2072/326418 |
| Acceso en línea: | http://hdl.handle.net/2072/326418 https://doi.org/10.1021/acscatal.7b00360 |
| Access Level: | acceso abierto |
| Palabra clave: | Quimica |
| Sumario: | A polystyrene-supported isothiourea (1a) behaves as a highly efficient organocatalyst in a variety of formal [4 + 2] cycloaddition reactions. The catalytic system has proven to be highly versatile, leading to six-membered heterocycles and spiro-heterocycles bearing an oxindole moiety in high yields and very high enantioselectivities (32 examples, including the previously unreported oxindole spiropyranopyrazolones 8; 97% mean ee). The notable chemical stability of 1a under operation conditions results in high recyclability (11 cycles, accumulated TON of 76.8) and allows the implementation of an extended-operation continuous flow process (no decrease in yield or ee after 18 h). |
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