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.

Expeditious synthesis and biological evaluation of new C-6 1,2,3-triazole adenosine derivatives A1 receptor antagonists or agonists

“…The installation of the triple bond at the C-6 position of the adenosine derivative was accomplished in 69% yield. 30 Deprotection of the TMS group was performed with tetrabutylammonium fluoride 31 to yield the terminal alkyne 4 in 43% yield.…”

Pd-Catalyzed Direct Arylation of Tautomerizable Heterocycles with Aryl Boronic Acids via C−OH Bond Activation Using Phosphonium Salts

“…It generally takes four steps to prepare the 6-arylpurine nucleosides, including protection, activation (halogenation or sulfonylation), cross-coupling, and deprotection (Scheme ). The preparation of these ribonucleosides has attracted considerable synthetic attention in recent years . By using the Pd-catalyzed phosphonium coupling, the synthesis of the 6-arylpurine ribonucleoside can now be efficiently achieved in a single step in 72% yield from unactivated and unprotected inosine and an aryl boronic acid.…”

Diversity Synthesis of Complex Pyridines Yields a Probe of a Neurotrophic Signaling Pathway

“…Attempts to reduce the temperature abolished catalytic activity, which is expected due to the stability of the CO ligands. NiCl 2 (dppp)/Zn,(14) CoCl 2 /Zn,(15) and RhCl(PPh 3 ) 3 ,(16) resulted in recovery of starting materials or complex mixtures of products.…”