The Regioselective Functionalization Reaction of Unprotected Carbazoles with Donor-Acceptor Cyclopropanes
Hua Zhao1, Peng Shen1, Dongru Sun1
1Institute of Drug Discovery Technology, Qian Xuesen Collaborative Research Center of Astrochemistry and Space Life Sciences, Ningbo University, Ningbo 315211, Zhejiang, China.
Abstract:
The regioselective functionalization reaction of unprotected carbazoles with donor-acceptor (D-A) cyclopropanes has been demonstrated for the first time. With Sc(OTf)3 as Lewis acid catalyst, the N-H functionalization of carbazoles takes place through a highly selective nitrogen-initiated nucleophilic ring opening reaction. Significantly, by engaging TfOH as Brønsted acid catalyst, a straightforward C-H functionalization at the 3-position of the unprotected carbazole proceeds via Friedel-Crafts-type addition. This strategy facilitates the diversity-oriented synthesis of carbazole-containing heterocycles and expands the novel application of D-A cyclopropanes.
Related Concept Videos
Cycloaddition Reactions: MO Requirements for Thermal Activation
Cycloaddition Reactions: Overview
Cyclohexenones via Michael Addition and Aldol Condensation: The Robinson Annulation
Regioselectivity of Electrophilic Additions-Peroxide Effect
Diels–Alder Reaction Forming Bridged Bicyclic Products: Stereochemistry
Regioselectivity and Stereochemistry of Hydroboration
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.


