Ferrocenoyl-adenines: substituent effects on regioselective acylation.

A series of -substituted adenine-ferrocene conjugates was prepared and the reaction mechanism underlying the synthesis was explored. The S2-like reaction between ferrocenoyl chloride and adenine anions is a regioselective process in which the product ratio (7/9-ferrocenoyl isomers) is governed by the steric property of the substituent at the -position. Steric effects were evaluated by using Charton (empirical) and Sterimol (computational) parameters.

Transacylation in Ferrocenoyl-Purines. NMR and Computational Study of the Isomerization Mechanism.

In the reaction of purines with ferrocenoyl chloride in dimethylformamide (DMF), a regioselective acylation occurred. The two products have been isolated and, according to detailed NMR analysis, identified as - and -ferrocenoylated isomers. In a more polar solvent, for example, in dimethylsulfoxide (DMSO), the two isomers interconvert to each other.