Compounds and methods for labeling oligonucleotides

1-6 1 2 3 4 4 5 5 6 7 A compound having the general formula shown below: where Rare independently selected from the group consisting of an electron withdrawing group, an alkyl group, an aryl group, hydrogen, a heteroaryl group, and a five or six member ring structure formed from the Rand Rpair, the Rand Rpair, the Rand Rpair, or the Rand Rpair; Ris a substituted or unsubstituted aryl group; and Y is a nucleophile.