Cobalt‐Induced Synthesis of 6‐(Pyridin‐2‐yl)purines by Microwave‐Enhanced [2+2+2] Cyclotrimerization

Abstract

Abstract A novel, efficient, and atom‐economic methodology for the preparation of a large series of diversely substituted (pyridin‐2‐yl)purines has been developed. Thus, microwave‐enhanced [2+2+2] cyclotrimerization of 6‐(diynyl)purines with nitriles in the presence of a stoichiometric or catalytic amount of [CpCo(CO) 2 ] afforded the corresponding products in good yields. The reactions carried out with various alkyl, aryl, and heteroaryl cyanides poceeded with exclusive regioselectivity, affording 6‐(pyridin‐2‐yl)purines. In an analogous manner, [2+2+2] cyclotrimerizations of 1,8‐bis(purinyl)‐1,7‐octadiynes with nitriles were conducted, yielding 1,4‐bis(purin‐6‐yl)‐5,6,7,8‐tetrahydroisoquinolines. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)