Cyclotrimerization of 6-ethynylpurines. Synthesis of 1,2,4-and 1,3,5-tris(purin-6-yl)benzenes as novel Hoogsteen-triplet analogues

Authors
Hocek, M Stara, IG Stary, I Dvorakova, H
Citation
M. Hocek et al., Cyclotrimerization of 6-ethynylpurines. Synthesis of 1,2,4-and 1,3,5-tris(purin-6-yl)benzenes as novel Hoogsteen-triplet analogues, TETRAHEDR L, 42(3), 2001, pp. 519-521
Citations number
22
Categorie Soggetti
Chemistry & Analysis","Organic Chemistry/Polymer Science
Journal title
TETRAHEDRON LETTERS
ISSN journal
00404039 → ACNP
Volume
42
Issue
3
Year of publication
2001
Pages
519 - 521
Database
ISI
SICI code
0040-4039(20010115)42:3<519:CO6SO1>2.0.ZU;2-V
Abstract
Cyclotrimerization reactions of the 9-protected 6-ethynylpurines 4a,b in th e presence of various transition metal catalysts were studied. The best res ults were obtained with Ni(COD)(2) or Ni(COD)(2)/PPh3 to obtain the 1,2,4- and 1,3,5-tris(purin-6-yl)benzenes 5a,b and 6a,b in moderate to good yields (in a 4:1 to 10:1 ratio). This method is suitable for the practical synthe sis of the unsymmetrical 1,2,4-tris(purin-6-yl)benzenes 5a-c, while the sym metrical 1,3,5-tris(purin-6-yl)benzenes 6a,b are generally formed as minor products. (C) 2001 Elsevier Science Ltd. All rights reserved.