title: Preparation of highly substituted 6-arylpurine ribonucleosides by Ni-catalyzed cyclotrimerization. Scope of the reaction.
abstract: Transition metal complex catalyzed cocyclotrimerization of protected alkynylpurine ribonucleosides 1 with various diynes 2 gave rise to a series of 6-arylpurine nucleosides 3 that were further deprotected to free nucleosides 4. Generally, the best yields of cyclotrimerizations were obtained with a catalytic system Ni(cod)2/2PPh(3). On the other hand, CoBr(PPh(3))3 proved to be a superior catalyst for cyclotrimerization of 1 with dipropargyl ether 2g. In addition, Ni catalysis is also suitable for direct cyclotrimerization of unprotected alkynylpurine ribonucleosides 5 to the corresponding 6-arylpurinylribosides 4.
authors.affiliation: Department of Organic and Nuclear Chemistry and Centre for New Antivirals and Antineoplastics, Faculty of Science, Charles University, Hlavova 8, 128 43 Praha 2, Czech Republic.
authors.forename: Pavel
authors.initials: P
authors.lastname: Turek
authors.forename: Petr
authors.initials: P
authors.lastname: Novák
authors.forename: Radek
authors.initials: R
authors.lastname: Pohl
authors.forename: Michal
authors.initials: M
authors.lastname: Hocek
authors.forename: Martin
authors.initials: M
authors.lastname: Kotora
mesh_terms: D002384:Catalysis; D003500:Cyclization; D008968:Molecular Conformation; D009532:Nickel / Q000737:chemistry*; D011687:Purines / Q000737:chemistry*; D012263:Ribonucleosides / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D011687:Purines; D012263:Ribonucleosides; D009532:Nickel