Scope of Ru(II)-catalyzed synthesis of pyridines from alkynes and nitriles.
Pyridines can be efficiently synthesized by Ru(II)-catalyzed [2 + 2 + 2] cycloaddition of 1,6-diynes to alpha,omega-dinitriles or electron-deficient nitriles or by Ru(II)-catalyzed [2 + 2 + 2] cocyclization of electron-deficient alkynes and electron-deficient nitriles. The reactions with dinitriles seem likely to proceed via ruthenacyclopentadiene intermediates and the reactions with electron-poor nitriles via azaruthenacyclopentadienes. The reaction with asymmetric electron-deficient alkynes affords 2,3,6-trisubstituted pyridines in good yield.
Varela
Jesús A
JA
Departamento de Química Orgánica y Unidad Asociada al CSIC, Facultad de Química, Universidad de Santiago de Compostela, 15782 Santiago de Compostela, Spain.
Castedo
Luis
L
Saá
Carlos
C