DFT studies on the mechanism of Ag2CO3‐catalyzed hydroazidation of unactivated terminal alkynes with TMS‐N3: An insight into the silver(I) activation mode. Issue 27 (18th July 2017)

• Record Type: Journal Article
• Authors: Yuan, Haiyan; Xiao, Pin; Zheng, Yiying; Zhang, Jingping
• Is Part Of: Journal of computational chemistry. Volume 38:Issue 27(2017)
• Page Start: 2289
• Page End: 2297
• Publication Date: 2017-07-18
• Subjects: ethynyl carbinols -- silver catalysis -- density functional theory -- mechanism -- hydroazidation; Chemistry -- Data processing -- Periodicals; 542.85
• DOI: 10.1002/jcc.24879
• Languages: English
• ISSNs: 0192-8651

Abstract

Abstract : Silver‐mediated hydroazidation of unactivated alkynes has been developed as a new method for the synthesis of vinyl azides. Density functional theory calculations toward this reaction reveal that terminal alkynes with TMS‐N3 participated hydroazidation proceed through HN3 formation, deprotonation and silver acetylides formation, nucleophilic addition, and protonation of terminal carbon by AgHCO3 . It is also found that water molecules and activation modes of Ag (I) have a significant influence on the title reaction mechanism. Initially, catalyst Ag2 CO3 coordinates preferentially with internal N atom of TMS–N3 to assist water as hydrogen source and proton‐shuttle in facilitating HN3 formation. Then, the regioselective anti ‐addition of HN3 to triple bond of active silver‐acetylide or ethynyl carbinols affords product vinyl azide via Ag–C σ‐bond activation or Ag…C π‐coordination activation modes, and the former one is more favorable. The origin of the difference regioselectivity is ascribed to the electronic and orbital effects of the reactive sites. Moreover, Ag2 CO3 is the critical catalyst, acting as activator, base, and stabilizer to promote the HN3 and vinyl azide formation. Water molecule plays an important role as proton shuttle to promote HN3 and key active silver acetylides formation, thus improving the yield of product. © 2017 Wiley Periodicals, Inc. Abstract : DFT calculations were conducted to disclose the mechanism, regioselectivity, and activation mode of silver (I) in Ag2 CO3 ‐catalyzed 2‐azidoallyl alcohols of ethynyl carbinols and TMS–N3 . It is found that water molecules and activation modes of Ag (I) have a significant influence on this transformation. Furthermore, the π‐silver activation and silver σ‐activation mode is dominate in the formation of HN3 and the vinyl azide, recpectively.