Predicted exocyclic amino group alkylation of 2′-deoxyadenosine and 2′-deoxyguanosine by the isopropyl cation

Diisopropyltriazene in aqueous 10% acetonitrile (pH 7.0 +/- 0.4) yields N-6-isopropyl-2'-deoxyAdo as the predominant product and N-2-isopropyl-2'-deoxyGuo in yields comparable with the O-6 adduct in reactions with 2'-deoxyAdo and 2'-deoxyGuo, respectively. These observations are inconsistent with what is expected on the basis of the regnant hypothesis concerning factors that determine atom site selectivity in diazonium ion-mediated alkylations. An alternative explanation based on the fleeting existence of the reactive intermediates involved is consistent with these observations.