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ZnI 2 /NEt 3 ‐Catalyzed Cycloaddition of CO 2 with Propargylic Alcohols: Computational Study on Mechanism
Author(s) -
Ma Jun,
Lu Lu,
Mei Qingqing,
Zhu Qinggong,
Hu Jiayin,
Han Buxing
Publication year - 2017
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201700771
Subject(s) - cycloaddition , chemistry , metalation , electrophile , deprotonation , protonation , intramolecular force , catalysis , reaction mechanism , solvent , reactivity (psychology) , medicinal chemistry , stereochemistry , organic chemistry , ion , medicine , alternative medicine , pathology
The ZnI 2 (NEt 3 )/NEt 3 ‐catalyzed cycloaddition of CO 2 with propargylic alcohols to α‐alkylidene cyclic carbonates was studied by DFT calculations for the first time to explore the detailed reaction mechanism. By comparing the distinct CO 2 ‐activated and OH‐activated pathways as well as the solvent effects of reactants and products, a complete picture of the metal‐salt/base‐catalyzed mechanism is provided, which involves four steps: deprotonation of propargylic alcohol, CO 2 electrophilic attack, concerted metalation and intramolecular cyclization, and protonation to form the cyclic carbonates. With the polar solvent effects of reactants or products, the third step is the rate‐determining step. The role of Zn II is activating the hydroxyl group, balancing of the charge of the alkylcarbonate anion and leading to the metalation. The base NEt 3 acts as the proton‐transfer bridge to promote the transfer of the proton. In addition, the selectivity of the five‐membered cyclic carbonates has been investigated.