title: Palladium-Catalyzed Aryl Amination Reactions of 6-Bromo- and 6-Chloropurine Nucleosides.
abstract: Palladium-catalyzed C-N bond forming reactions of 6-bromo- as well as 6-chloropurine ribonucleosides and the 2'-deoxy analogues with aryl amines are described. Efficient conversions were observed with Pd(OAc)(2)/Xantphos/Cs(2)CO(3), in PhMe at 100 °C. Reactions of the bromo nucleoside derivatives could be conducted at a lowered catalytic loading (5 mol % Pd(OAc)(2)/7.5 mol % Xantphos), whereas good product yields were obtained with a higher catalyst load (10 mol % Pd(OAc)(2)/15 mol % Xantphos) when the chloro analogue was employed. Among the examples evaluated, silyl protection for the hydroxyls appears better as compared to acetyl. The methodology has been evaluated via reactions with a variety of aryl amines and by synthesis of biologically relevant deoxyadenosine and adenosine dimers. This is the first detailed analysis of aryl amination reactions of 6-chloropurine nucleosides, and comparison of the two halogenated nucleoside substrates.
authors.affiliation: Department of Chemistry, The City College and The City University of New York, 160 Convent Avenue, New York, New York 10031, U.S.A.
authors.forename: Paul F
authors.initials: PF
authors.lastname: Thomson
authors.forename: Pallavi
authors.initials: P
authors.lastname: Lagisetty
authors.forename: Jan
authors.initials: J
authors.lastname: Balzarini
authors.forename: Erik
authors.initials: E
authors.lastname: De Clercq
authors.forename: Mahesh K
authors.initials: MK
authors.lastname: Lakshman