The alkyne-type organic compounds are widely applied in chemistry, biology and materials. However, selective synthesis of these compounds remains a great challenge because alkynes are highly active and have various reaction pathways. The traditional solution-based synthesis of these alkyne-type compounds usually involves complex reactants, multiple steps and various side reactions, yet the yields were still not high. For the first time, the researchers have successfully synthesized cis-enediynes on a Ag(111) surface with a yield up to 90%. Cis-enediyne-type compounds, are one kind of alkyne-type organic compounds and can be used as potent antitumor antibiotics. Moreover, with the combined comparative experiments and theoretical calculations, the mechanism of this reaction has been revealed.
The scheme of synthesis of cis-enediyne on the Ag(111) surface and the corresponding STM results. Copyright by Angew. Chem. Int. Ed.
The researchers chose a sort of Br substituted terminal alkyne as the precursor. Vapor deposition of the precursor onto the Ag(111) surface held at 420 K leads to the formation of ordered close-packed islands of cis-enediynes and the yield of cis-enediynes approaches 90%. With the cleavage of C-Br bonds under the reaction conditions, the co-adsorbed Br atoms help the formed cis-enediynes aggregating into close-packed islands through the intermolecular Br⋯H hydrogen bonds, which pose a high steric barrier for the further reactions of cis-enediynes. Comparative experiment shows that the products have no selectivity without the help of Br substituent. DFT-calculations further confirm that the aggregation effect can enhance the energy barrier of further reaction of cis-enediynes.
The described synthetic approach for directing reaction pathways on-surface may illuminate potential syntheses of other unstable organic compounds.
The paper was published online in Angew. Chem. Int. Ed. (2017, DOI: 10.1002/anie.201701142), titled as “Highly Selective Synthesis of cis-Enediynes on a Ag(111) Surface”. The first author is the graduate student, WANG Tao. The work is financially supported by the National Natural Science Foundation of China, the National Basic Research Program of China and China Scholarship Council.
Prof. ZHU Junfa
(National Synchrotron Radiation Laboratory, School of Chemistry and Material Science)
On May 11, the Nature Publishing Group released Nature Publishing Index 2010 China, remarking “a dramatic rise in the quality of research being published by China”. University of Science and Technology of China is ranked 3rd of TOP 10 Institutions in Index 2010 China.
This article came from News Center of USTC.