Oxidative diphosphonylation of 1,4-dihydropyridines and pyridinium salts
An oxidative double phosphonylation of dihydropyridines 1 and pyridinium salts 2 is achieved through the use of dialkyl phosphites, DDQ, and triethylamine. Acceptable to good yields of 2, 6-diphosphonylated-1,2-dihydropyridines 3 are obtained in a one-pot reaction involving tandem nucleophilic addition/oxidation processes. Isomerization of 3 to the more stable 2,4-diphosphonylated-1, 4-dihydropyridine 4 was observed in some cases.
Lavilla
R
Laboratory of Organic Chemistry, Faculty of Pharmacy, University of Barcelona, Avda. Joan XXIII s/n, 08028 Barcelona, Spain.
Spada
A
Bosch
J