Deamination of 1-Alkyl-9-aminomethyltriptycenes : Participation of a Neighboring 1-Alkyl Substituent

Deamination reactions of l-alkyl-9-aminomethyltriptycenes (alkyl = Me, Et, i-Pr, and t-Bu) and 9-(1-aminoethyl)-1-methyltriptycene were performed in CHC13 and in AcOH, and product distributions were studied. The results suggest that the loss of N 2 from a primary alkanediazonium ion predominantly takes place concomitantly with participation of a C-H bond of the neighboring 1-alkyl group to form a nonclassical cationic species with a three-center two-electron bonding, while the loss of N 2 from a secondary alkanediazonium ion occurs spontaneously to form a secondary carbocation. Solvent effects (CHCl 3 vs AcOH) are explained in terms of lower nucleophilicity/basicity of the AcO - in AcOH than in CHCl 3 due to solvation.