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Facile one-pot coupling-aminovinylation approach to push-pull chromophores: alkyne activation by sonogashira coupling
Alexei S Karpov1, Frank Rominger, Thomas J J Müller
1Organisch-Chemisches Institut der Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, D-69120 Heidelberg, Germany.
The Journal of Organic Chemistry
|February 15, 2003
Abstract:
A straightforward coupling-aminovinylation sequence of terminal alkynes 1, electron-deficient heteroaryl halides 2, and secondary amines 4 furnishes highly solvochromic push-pull chromophores 5 in good yields. Semiempirical calculations (PM3) suggest that the aminovinylation proceeds in a stepwise fashion through a zwitterionic intermediate with a final rate-determining intramolecular protonation. Crucial parameters for the success of the amine addition are the relative LUMO energies and the charge distribution at the beta-alkynyl carbon atom.