ChemInform Abstract: SYNTHESIS OF SYMMETRICALLY TRISUBSTITUTED BENZENE DERIVATIVES, (N‐BU3P)2NIBR2, A NEW CATALYST FOR THE SYMMETRICAL CYCLOTRIMERIZATION OF HYDROXYACETYLENES

Abstract

Die ungesättigten Alkohole (I) werden beim Rückflußkochen in Petroläther (PÄ) oder einem anderen geeigneten Lösungsmittel (ohne Lösungsmittel verläuft die Reak tion nach einer längeren Induktionsperiode bei Raumtemperatur stürmisch bis explosiv) in Gegenwart des Bis(tri‐n‐butylphosphin)‐NiBrz‐Komplexes zu den Benzolderivaten (II) trimerisiert.

Preparation of Highly Substituted 6-Arylpurine Ribonucleosides by Ni-Catalyzed Cyclotrimerization. Scope of the Reaction

“…From a synthetic point of view, it is desirable to avoid deprotection and to cyclotrimerize unprotected 6-alkynylpurine ribonucleosides with diynes directly to 6-arylpurine nucleosides. Since it has been shown that the presence of free hydroxyl groups in a molecule of an alkyne did not inhibit the reaction, ,, the unprotected 6-(phenylethynyl)purine riboside 5 was cyclotrimerized with 2a and 2c by a catalytic amount of Ni(cod) 2 /2PPh 3 (Scheme ). The reaction took place; however, the desired unprotected arylpurine ribosides 4aa and 4ac were obtained in rather mediocre yields of 31 and 45%, respectively.…”