Regioselective Oxidative Halotriflamidation of Dienes and Trienes as a Route to New Amidines and Heterocycles

Comparative analysis of halotriflamidation of linear and cyclic dienes and trienes in different oxidative systems revealed a large variety of reactivity patterns. With linear dienes the haloamidation or solvent (MeCN) interception products or the products of their further transformations are formed. The NBS-induced reactions of conjugated cyclic dienes (cyclopentadiene, 1,3-cyclohexadiene, 1,3-cyclooctadiene) regioselectively afford bromoamidines at only one double bond with solvent interception. Dicyclopentadiene also gives bromamidine at the bicycloheptene double bond. With linear 5-methylhepta-1,3,6-triene, 1,4-conjugate addition occurs with solvent interception and the halogen atom directed to the terminal olefinic carbon. Cyclododeca-1,5,9-triene reacts with triflamide differently depending on the oxidant to give amidine or azabicyclo[8.2.1]tridec-5-ene structure. The synthesized bromoamidines were converted into the corresponding imidazolines in close to quantitative yield.