Chiral dendrigraft polymer for asymmetric synthesis of isoquinuclidines

摘要

The synthesis of multi-arm star dendrigraft amidoamine polymer with pentaerythritol initiated polyepichlorohydrin as the core, PEN-G(2), on a solid resin support has been demonstrated. We have functionalized a Merrifield resin support with polyepichlorohydrin, and dendrons are grown on it up to second generation using a "graft from" approach. The estimation of amine functionality was done and found to be 25 mmol g(-1) which was 70% of the theoretical value. Photolytic cleavage of the dendrigraft polymer from the support resulted in a brown water-soluble viscous liquid. The molecular weight of 3966 shows that out of the 9 G(1) dendritic substituents, 5 of them were converted to generation G(2). The TEM image of the G(2) polymer shows an inhomogeneous polygon-like appearance. The chiral modification of the dendrigraft polymer, PEN-G(2), has been done. The copper complex of chiral modified PEN-G(2) dendrigraft polymer was synthesized and characterized. The copper complex of PEN-G(2) dendrigraft polymer was found to be an excellent catalyst for the synthesis of isoquinuclidines via aza Diels-Alder reaction between cyclohexenone and imines. The catalyst exhibited superior enantioselectivity. The reusability of the catalyst was studied for five reaction cycles.