Influence of basicity and steric effects on the metathesis of olefinic amines

Metathesis of olefinic amines has been studied with two purposes: (i) to try to carry out at a stoichiometric (or slightly catalytic) level metathesis of olefinic amines to obtain telechelic compounds; (ii) to try to find which parameters play a role in the catalytic process. Two types of catalytic systems were found to be moderately active in the metathesis of olefinic amines: W(CO)₅L {A figure is presented} or W(CO)₃(Arene) (Arene = benzene, toluene, mesitylene) associated with a large excess of C₂H₅AlCl₂ and O₂. M(NO)₂X₂L₂ associated with an excess of C₂H₅AlCl₂ (X = Cl, Br; M = Mo, W). The substituents on the nitrogen were found to determine the resulting reactivity of the olefinic amine: steric as well as electronic effects play a role on the acid-base equilibrium between the amine and the Lewis acid cocatalyst. The distance between the double bond and the amine group shows a sharp maximum for olefins of the type CH₂CH(CH₂)₃N(R)(R′). The results are tentatively explained on the basis of an intramolecular stabilization of the metallocarbene moiety by the amine group; this would increase the lifetime of the catalyst. Stereochemical studies seem to indicate that there is no modification of stereochemistry between functionalized and non-functionalized olefins. Consequently the intramolecular stabilization of the metallocarbene moiety and the amine group does not occur in the metallo-cyclobutane transition state formation.