Pd/C促进的四氢异喹啉高选择性部分脱氢(英文)

Highly selective partial dehydrogenation of tetrahydroisoquinolines using modified Pd/C

采用K3PO4?3H2O修饰的Pd/C为催化剂实现了取代四氢异喹啉高选择性部分脱氢,并成功地避免了当量有害氧化剂的使用.多相催化剂Pd/C对四氢异喹啉化合物具有催化脱氢活性,但反应选择性较差,同时产生完全脱氢的芳构化产物异喹啉.而K3PO4?3H2O修饰的Pd/C催化剂能有效提高脱氢反应的化学选择性,在最优条件下可获得最高89%的分离收率.这为取代3,4-二氢异喹啉的合成提供了一种简便、高原子经济性和高化学选择性的反应途径.此外,该多相催化剂可回收循环使用多次,且活性和选择性基本保持不变.

A highly selective procedure has been developed for the partial dehydrogenation of 1- substitut-ed-1,2,3,4-tetrahydroisoquinolines over K3PO4·3H2O-modified Pd/C catalyst. This new method provides facile, atom-economical and environmentally friendly access to 1-substituted-3,4- dihy-droisoquinolines without the need for stoichiometric amounts of harmful oxidants. The use of standard Pd/C as a catalyst for this process gave poor chemoselectivity. Pleasingly, the use of a K3PO4·3H2O-modified Pd/C catalyst promoted the partial dehydrogenation of 1-substituted-1,2,3,4-tetrahydroisoquinolines with excellent chemoselectivity by suppressing further dehydroaromatiza-tion. Furthermore, conducting the reaction under an atmosphere of oxygen led to further improve-ments in the chemoselectivity of the dehydrogenation, with the ratio of imine to isoquinoline reaching up to 32/1. The heterogenous Pd/C catalyst could also be recycled and reused at least three times with excellent conversion and chemoselectivity, demonstrating the significantly practi-cal potential of this methodology.