**7. Conclusions**

In this review, a number of catalytic applications have demonstrated that the combination of NHC catalysis with Lewis acid is a unique and efficient strategy for access to a wide range of highly functionalized complex and enantiomerically enriched structural motifs. The use of a Lewis acid in combination with a NHC catalyst enable us to (1) increase the yield and enantioselectivity, (2) reverse diastereo- and regioselectivity, (3) change the reaction pathway and (4) activate a previous inactive electrophile in NHC-generated processes. Overall, the dual catalytic approaches would expand the utility of NHC/Lewis acid methodology and construct other synthetically useful products with diverse particularly important skeletons. Further development of the cooperative catalysis in the total synthesis of natural products and pharmaceuticals will be the target of future studies.

**Author Contributions:** Q.J. and Q.R. wrote the manuscript. Y.L. (Yaqiong Li) and Y.L. (Yinhe Lin) contributed to discussions and edited the manuscript.

**Funding:** The project is funded by the National Natural Science Foundation of China (No. 21602179) and Science Foundation of Yangtze Normal University (No. 2017KYQD123, 2018QNRC17).

**Conflicts of Interest:** The authors declare no conflict of interest.
