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Gold‐Catalyzed Functionalization of Semicarbazides with Terminal Alkynes to Achieve Substituted Semicarbazones
Author(s) -
Zimin Dmitry P.,
Dar'in Dmitry V.,
Eliseeva Anastasiya A.,
Novikov Alexander S.,
Rassadin Valentin A.,
Kukushkin Vadim Yu.
Publication year - 2019
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201901108
Subject(s) - chemistry , catalysis , density functional theory , delocalized electron , molecule , surface modification , hydrogen bond , proton nmr , computational chemistry , functional group , crystallography , stereochemistry , organic chemistry , polymer
Gold‐catalyzed functionalization of semicarbazides (ArNHCONHNH 2 ) with various terminal alkynes R 2 C≡CH (R 2 = Alk or Ar) in the presence of Ph 3 PAuNTf 2 (3 mol‐%) grants a range of substituted semicarbazones (16 examples; 64–93 %). This novel metal‐catalyzed coupling proceeds under mild conditions (PhCl, 60 °C) and demonstrates a high functional group tolerance; the reaction is sensitive to the electronic effects of the substituents in terminal alkynes. Inspection of XRD solid‐state structures of three obtained semicarbazones proved their dimerization via weak to moderate strength hydrogen bonding. The structures of the semicarbazones in solutions were studied by concentration dependent 1 H NMR and 2D NMR and these experiments proved the presence of H‐bonds between two molecules. The nature and energy of H‐bonding (3.8–5.1 kcal/mol), degree of electron density delocalization, and rotational barriers via various bonds in the equilibrium model structures were studied by DFT calculations at the M06‐2X/6‐311++G** level of theory.