Direct Access to Bridged Polycyclic Skeletons by Merging Oxidative C-H Annulation and Cascade [4 + 2] Cycloaddition

Ni-Catalyzed 1,5-Sigmatropic Ester Shift on Cyclopentadiene Rings: Regioselective Conversion of 5,5-Disubstituted Cyclopentadienes to CH2-Cyclopentadienes

Described herein is a nickel(II)-catalyzed regioselective rearrangement of 5,5-disubstituted cyclopentadienes to fully functionalized CH2-cyclopentadienes via successive 1,5-sigmatropic shifts of the ester group on the quaternary carbon and hydrogen under mild basic conditions. The obtained CH2-cyclopentadienes were also readily applied in the preparation of highly functionalized dibenzo[e,g]azulene derivatives in two steps.

Regiodivergent Ring-Expansion of Oxindoles to Quinolinones

The development of divergent methods to expedite structure-activity relationship studies is crucial to streamline discovery processes. We developed a rare example of regiodivergent ring expansion to access two regioisomers from a common starting material. To enable this regiodivergence, we identified two distinct reaction conditions for transforming oxindoles into quinolinone isomers. The presented methods proved to be compatible with a variety of functional groups, which enabled the late-stage diversification of bioactive oxindoles as well as facilitated the synthesis of quinolinone drugs and their derivatives.

Rh-Catalyzed [3+2] Annulation of Cyclic Ketimines and Alkynyl Chloride: A Strategy for Accessing Unsymmetrically Substituted and Highly Functionalizable Indenes

Alkynyl chlorides were found to be extraordinarily novel electrophiles, which could afford a single regioisomer of the [3+2] annulation adducts with cyclic ketimines by rhodium catalysis. The alkenyl chloride moiety in the products provided a valuable functional handle for further diverse transformations. Therefore, this research provided not only a synthetic protocol for accessing unsymmetrically substituted indenyl amines but also a highly divergent solution for decorating the substituting group by postmanipulation of the chloride.

Synthesis of bridgehead-azacycles via dual C-N/C-C annulation of α-amino acids, aminals and maleimides

The synthesis of various bridged azacyclic adducts has recently become a reemerging topic due to their bioactive and natural product mimic profiles. Accordingly, herein, we report a method for easy access to succinamide-bridged azacyclic derivatives through the metal-free polarization-controlled dual C-N/C-C annulation of readily available α-amino acids, 2-amino benzaldehydes or pyrrole/indole-2-aldehyde and maleimide substrates. This cascade features a rare dipolarophile-induced diastereo-selective amidative annulation, followed by 3 + 2 cycloaddition as key steps.

Brønsted acid promoted substrate-dependent regiodivergent alkynylcyclopropane–cyclopentadiene rearrangement assisted by the internal carbonyl group

Facile Brønsted acid promoted alkynylcyclopropane–cyclopentadiene rearrangement, avoiding the five-membered cycloallene intermediate assisted by the internal carbonyl groups, has been developed.