Understanding the Participation of Quadricyclane as Nucleophile in Polar [2σ+2σ+2π] Cycloadditions toward Electrophilic π Molecules

被引:225
作者
Domingo, Luis R. [1 ]
Saez, Jose A. [1 ]
Zaragoza, Ramon J. [1 ]
Arno, Manuel [1 ]
机构
[1] Univ Valencia, Dept Quim Organ, E-46100 Valencia, Spain
关键词
D O I
10.1021/jo801575g
中图分类号
O62 [有机化学];
学科分类号
070303 ; 081704 ;
摘要
The formal [2 sigma + 2 sigma + 2 pi] cycloaddition of quadricyclane, 1, with dimethyl azodicarboxylate, 2, in water has been studied using DFT methods at the B3LYP/6-31G** and MPWB1K/6-31G** levels. In the gas phase, the reaction of 1 with 2 has a two-stage mechanism with a large polar character and an activation barrier of 23.2 kcal/mol. Inclusion of water through a combined discrete-continuum model changes the mechanism to a two-step model where the first nucleophilic attack of 1 to 2 is the rate-limiting step with an activation barrier of 14.7 kcal/mol. Analysis of the electronic structure of the transition state structures points out the large zwitterionic character of these species. A DFT analysis of the global electrophilicity and nucleophilicity of the reagents provides a sound explanation about the participation of 1 as a nucleophile in these cycloadditions. This behavior is reinforced by a further study of the reaction of 1 with 1,1-dicyanoethylene.
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页码:8791 / 8799
页数:9
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