Preparation of highly substituted 6-arylpurine ribonucleosides by Ni-catalyzed cyclotrimerization. Scope of the reaction.
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.
Turek
Pavel
P
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.
Novák
Petr
P
Pohl
Radek
R
Hocek
Michal
M
Kotora
Martin
M
D002384:Catalysis; D003500:Cyclization; D008968:Molecular Conformation; D009532:Nickel / Q000737:chemistry*; D011687:Purines / Q000737:chemistry*; D012263:Ribonucleosides / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
D011687:Purines; D012263:Ribonucleosides; D009532:Nickel