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Surface‐Dependent Chemoselectivity in C−C Coupling Reactions
Author(s) -
Chen Zhi,
Lin Tao,
Zhang Liding,
Zhang Lei,
Xiang Bingxi,
Xu Hu,
Klappenberger Florian,
Barth Johannes V.,
Klyatskaya Svetlana,
Ruben Mario
Publication year - 2019
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201900636
Subject(s) - chemoselectivity , alkyne , alkene , chemistry , density functional theory , covalent bond , coupling reaction , computational chemistry , organic chemistry , catalysis
Surface‐confined covalent coupling reactions of the linear compound 4‐(but‐3‐en‐1‐ynyl)‐4′‐ethynyl‐1,1′‐biphenyl ( 1 ), which contains one alkyne and one enyne group on opposing ends, have been investigated using scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. The reactions show a surface‐dependent chemoselectivity: on Au(111), compound 1 preferentially yields cyclotrimerization products, while on Cu(111), a selective coupling between the enyne and alkyne groups is observed. Linear, V‐shaped string formations combined with Y‐shaped bifurcation motifs result in a random reticulation on the entire surface. DFT calculations show that the C−H⋅⋅⋅π δ− transition state of the reaction between the deprotonated alkyne group and a nearby H‐donor of the alkene group plays a key role in the mechanism and high chemoselectivity. This study highlights a concept that opens new avenues to the surface‐confined synthesis of covalent carbon‐based sp–sp 2 polymers.