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Updated: Oct 24, 2026

Efficient Construction of Drug-like Bispirocyclic Scaffolds Via Organocatalytic Cycloadditions of α-Imino γ-Lactones and Alkylidene Pyrazolones
Published on: February 7, 2019
Cyclic and bicyclic alkyl(amino)carbene derived N-heterocyclic olefins: synthesis, reactivity and electronic
Ankita Sharma1, Subrata Kundu1,2
1Department of Chemistry, Indian Institute of Technology Delhi, New Delhi 110016, India. subrata@iitd.ac.in.
Abstract:
A series of N-heterocyclic olefins (NHOs) was synthesized using a platform of a five-membered cyclic (alkyl)(amino)carbene (MeCAAC), a bicyclic alkyl(amino)carbene (EtBICAAC) and a six-membered cyclic (alkyl)(amino)carbene (6-CAAC). The isolated NHOs [MeCAACCH2 (1), EtBICAACCH2 (2) and 6-CAACCH2 (3)] exhibited air and moisture stability, unlike NHOs derived from classical imidazole-based N-heterocyclic carbenes (iNHCs). The calculated proton affinity of 1-3 (257-260 kcal mol-1) indicated a comparable basicity to traditional iNHOs. The DFT analysis showed that the HOMO of 1-3 is primarily located on the exocyclic olefinic carbon. A comprehensive study has been performed to understand the electronic properties of these NHOs and the results have been compared with those of the traditional iNHOs using quantum chemical analysis and experimental techniques such as NMR, UV and IR spectroscopic studies. We have functionalized the NHOs [IPrCH2, CAACCH2, and EtBICAACCH2] with a tricyanoethylene group [carbeneCH-C(CN)C(CN)2] to understand the influence of the NHCs on the electronic absorption of the cyano-functionalized ethylene group. We isolated the bromine-functionalized MeCAACCHBr and EtBICAACCHBr from the reaction with CNBr and extended the reactivity study of MeCAACCH2 with C2O2Cl2, SbCl3 and OC(OCCl3)2.
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