A simple and alternative way for the methylation of functionalized purine bases
Thomas Scattolin
1, Fabiano Visentin
1, Luciano Canovese
1and Claudio Santo
11
Dipartimento di Scienze Molecolari e Nanosistemi, Universita` Ca’ Foscari, Venezia
e-mail: thomas.scattolin@unive.it
Purines represent a class of organic compounds found in nature mainly as nitrogen bases of nucleic acids or as xanthine derivatives.
They are constituted by two condensed heterocyclic rings bearing two nitrogen each that may be functionalized in order to obtain a wide range of compounds.
1a-hIn this abstract we present a simple and alternative synthetic route to obtain purine- based imidazolium salts that, while displaying a remarkable biological activity, are also widely used in organometallic chemistry as precursors of the NHC ligands.
2The compounds taken into consideration in this work have been synthesized by alkylation, in basic environment, of the theophylline imidazole ring.
1a-hIn order to further functionalize the latter derivatives in the aim at obtaining the corresponding imidazolium salts, the alkylation of the N-9 is required and according to literature, such a process is very difficult (drastic conditions and modest yields).
1c, 3a-cIn this contribution we report a novel synthetic approach carried out under mild conditions for the final methylation of the theophylline derivatives based on the use of stoichiometric quantities of Me
3OBF
4at room temperature. (Scheme 1)
N
N N
N
O O
1a-1e
7 8 9 1
2
3 4
6 5
R
1.1 eq Me3OBF4 in CH3CN R.T., 30 min
N
N N
N
O O
2a-2e
7 8 9 1
2 3
4 6 5
R
BF4-
R=Me 2a (73%) R=Bn 2b (77%) R=Propargyl 2c (60%) R=Phpropargy 2d (68%) R=CH2CN 2e (65%)
