Rapid access to pyrazolo[3,4-c]pyridines via alkyne annulation: limitations of steric control in nickel-catalyzed alkyne insertions.
Org Lett
; 9(24): 4947-50, 2007 Nov 22.
Article
em En
| MEDLINE
| ID: mdl-17979276
ABSTRACT
Polyfunctionalized pyrazolo[3,4-c]pyridines were readily prepared by the annulation of alkynes with tert-butyl 4-iodopyrazolocarboximines. The reaction was found to be catalyzed by both NiBr2(PPh3)2/Zn or PdCl2(PhCN)2 to yield complex heterocycles in good to moderate yields. Annulation using nickel catalysis was found to be regio-random, implying that steric control in nickel-catalyzed alkyne insertion has limitations based on the character of the Ni-C bond in the pre-insertion complex.
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Base de dados:
MEDLINE
Assunto principal:
Pirazóis
/
Piridinas
/
Alcinos
/
Níquel
Idioma:
En
Ano de publicação:
2007
Tipo de documento:
Article