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

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

Cross-Cyclotrimerization with Two Nitriles as a Synthetic Pathway to Unsymmetrically 3,3’-Disubstituted bis(Tetrahydroisoquinolines)

“…The microwave assisted cyclotrimerization of alkynes with nitriles offers several advantages in comparison with standard thermal conditions. Among these are, for example, reduced reaction times from hours to minutes, reactants are thus exposed to high reaction temperatures for shorter periods of time reducing possibility of thermal decomposition, and also the use of lower boiling point solvents such as THF, which allows easier separation of products [ 35 , 36 , 37 , 38 , 39 , 40 ].…”

CHAPTER 5. Cobalt-Catalyzed Heterocycle Synthesis

“…Replacing thermal heating with microwave heating was found to increase the reaction efficiency and shorten the reaction time. 81,82 In 2009, the first [2 þ 2 þ 2] co-cyclizations between ynamides, nitriles and alkynes were reported by Aubert, Malacria and co-workers. 83 They opened up a new access route to unprecedented nitrogen-containing heterocycles of the type 2-trimethylsilyl-3-aminopyridines.…”

Transition Metal-Mediated Synthesis of Monocyclic Aromatic Heterocycles

“…However, the CpCo(CO) 2 -catalyzed reactions usually require harsh reaction conditions (T>120 °C). 740 It was shown that milder reaction conditions could be achieved with the help of ligands and additives. 731 …”