Domingo LR, Picher MT, Andres J
Departamento de Quimica Organica, Universidad de Valencia, Dr. Moliner 50, 46100 Burjassot, Valencia, Spain, and Departament de Ciencies Experimentals, Universitat Jaume I, Apartat 224, 12080, Castello, Spain.
J Org Chem. 2000 Jun 2;65(11):3473-7. doi: 10.1021/jo000030k.
The mechanism of the domino reaction between acetylenedicarboxylic acid and 1,3-bis(2-furyl)propane has been theoretically studied in the framework of density functional theory. This domino process comprises two consecutive cycloaddition reactions: the first one is initialized by the nucleophilic attack of the C5 position of the furan ring to a conjugate position of acetylenedicarboxylic acid to give a zwitterionic intermediate, which by a subsequent ring-closure process affords an oxanorbornadiene intermediate. The second reaction is an intramolecular concerted cycloaddition of this intermediate to give the final dioxapentacyclic adduct. For the second cycloaddition, which corresponds to the step controlling the selectivity, eight alternative reaction pathways are found. Chemoselectivity, facial selectivity, and stereoselectivity of this domino reaction are related with the different approach modes of the tethered furan to the oxanorbornadiene system of the intermediate. The most favorable pathway takes place along an endo/syn approach of the furan ring relative to the bridged oxygen atom of the oxanorbornadiene system, with participation of the substituted double bond. An analysis of energetic contributions to the potential energy barriers for the intramolecular cycloadditions identifies the different factors controlling the reactive channels. Selectivity outcome is reproduced by these calculations.
在密度泛函理论框架下，对乙炔二羧酸与1,3-双（2-呋喃基）丙烷之间的多米诺反应机理进行了理论研究。该多米诺过程包括两个连续的环加成反应：第一个反应由呋喃环C5位对乙炔二羧酸的共轭位置进行亲核进攻引发，生成两性离子中间体，该中间体通过随后的闭环过程得到氧杂降冰片二烯中间体。第二个反应是该中间体的分子内协同环加成反应，生成最终的二氧杂五环加合物。对于对应于控制选择性步骤的第二个环加成反应，发现了八条替代反应途径。该多米诺反应的化学选择性、面选择性和立体选择性与连接的呋喃与中间体的氧杂降冰片二烯体系的不同接近方式有关。最有利的途径是呋喃环相对于氧杂降冰片二烯体系的桥连氧原子以内型/顺式方式接近，并伴随着取代双键的参与。对分子内环加成反应势能垒的能量贡献分析确定了控制反应通道的不同因素。这些计算重现了选择性结果。
