Enamines from Iodine Oxidation of Trialkylamines. 1. Electrophilic Capture by Cationic Heterocyclic Rings

Article abstract of DOI:10.1021/jo00189a004

Simple enamines derived from acetaldehyde, acetone, and propionaldehyde were generated in situ by iodine oxidation of triethylamine, N,N-diisopropylmethylamine, and tri-n-propylamine, respectively.The enamines were captured by a variety of cationic substrates including trityl, indolizinium, dithiolium, pyrylium, thiapyrylium, selenapyrylium, and tellapyrylium cations.The use of a second equivalent of iodine (or excess) oxidized the initial products of enamine capture to various iminium dyes.These dyes were easily hydrolyzed to heterocyclylidene aldehydes and ketones.Cyclic amines such as N-methylpyrrolidine gave enamines derived from ring oxidation. 2-Cyano-N,N-dimethylethylamine generated a cyano-substituted enamine under the reaction conditions.