Catalysis of the Diels–Alder Reaction of Furan and Methyl Acrylate in Lewis Acidic Zeolites

Diels–Alder (DA) reactions
of furans yield oxanorbornene
derivatives which can be converted to a variety of molecules, ranging
from molecules of biological interest to naturally occurring organic
compounds, and to aromatics via dehydration, a promising alternative
for the synthesis of aromatics from renewables. With furan being one
of the less reactive dienes, the development of Lewis acidic heterogeneous
catalysts, without the shortcomings of the traditional homogeneous
catalysts, is critically important. Herein, we use computational chemistry
to study the DA reaction of furan and methyl acrylate in three zeotypic
Lewis acids, Sn-, Zr-, and Hf-BEA. We find that all three exhibit
the same ability to enhance the electrophilic character of the dienophile
and promote modest charge transfer from the diene. Despite being moderately
Lewis acidic, they still achieve a reduction of about 12.5 kcal/mol
in the activation energy relative to the reaction in the absence of
catalyst.

呋喃参与的狄尔斯-阿尔德（Diels–Alder, DA）反应可生成氧代降冰片烯衍生物，此类衍生物可转化为多种分子，涵盖具有生物活性的化合物、天然存在的有机化合物，还可通过脱水反应制备芳烃，是从可再生资源合成芳烃的极具潜力的替代路径。由于呋喃是反应活性较低的二烯体之一，开发无传统均相催化剂弊端的路易斯酸型（Lewis acidic）多相催化剂至关重要。本文采用计算化学方法，研究了三类类沸石型路易斯酸——Sn-、Zr-及Hf-BEA——催化下呋喃与丙烯酸甲酯的DA反应。研究发现，这三类催化剂均可增强亲双烯体的亲电性，并促进二烯体发生适度的电荷转移。尽管它们的路易斯酸性仅为中等强度，但相较于无催化条件下的反应，仍可使反应活化能降低约12.5 kcal/mol。