Theoretical insights into the metal-free and formal [2+2+2] cycloaddition strategy via intramolecular cascade propargylic ene/Diels-Alder reactions with tautomerization

被引:8
作者
Li, Xinyao
Xu, Jiaxi [1 ]
机构
[1] Beijing Univ Chem Technol, State Key Lab Chem Resource Engn, Fac Sci, Beijing 100029, Peoples R China
基金
中国国家自然科学基金; 北京市自然科学基金;
关键词
1,3-DIPOLAR CYCLOADDITIONS; ENE REACTIONS; DIELS-ALDER; ALKYNES; ENERGIES; DISTORTION/INTERACTION; CYCLOTRIMERIZATION; REGIOSELECTIVITY; THERMOCHEMISTRY; CONSTRUCTION;
D O I
10.1039/c1ob05254c
中图分类号
O62 [有机化学];
学科分类号
070303 ; 081704 ;
摘要
A metal-free and formal [2 + 2 + 2] cycloaddition of triynes has emerged recently as a novel methodology for the synthesis of fused tricyclic compounds via an intramolecular cascade propargylic ene reaction, Diels-Alder cycloaddition and tautomerization. DFT calculations on three model systems reveal that the ene reaction with low distortion energy makes the metal-free strategy feasible and, as the rate-determining step, affects the regioselectivity of unsymmetric triynes. Furthermore, the types of final products depend on H-transfer during tautomerization after the Diels-Alder reaction. Generally, the different tethered atoms between the yne moieties are responsible for the different regioselectivities and the final products in the [2 + 2 + 2] cycloadditions. On the basis of a comprehensive theoretical investigation into the mechanism, triynes involving cyclic ynes have been designed and are predicted to react to afford fused tetracyclic products under milder conditions due to dramatically lower energy barriers and by altering the rate-determining step to the Diels-Alder reaction.
引用
收藏
页码:5997 / 6003
页数:7
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