REDUCTION PAR LES IONS CHROMEUX DE DERIVES BROMOPROPARGYLIQUES EN COMPOSES ALLENIQUES. APPLICATION A LA SYNTHESE DE LA PHEROMONE DE LA BRUCHE DU HARICOT SEC

Article abstract of DOI:10.1016/S0040-4020(01)91936-2

The racemic title compound 2(E) is obtained (77percent) by reduction with chromous ions (THF+HMPT solvent, with anhydrous AcOH) of 7(E) readily prepared from 4 or propargylic diethylacetal as starting materials.In the reduction of 7(E) or 7(Z) with Cr(2+), the nature and ratios of the compounds obtained (2(E), 2(Z), 8(E), 9(E+Z), 10(E)) are strongly dependent on solvent (THF, or THF+HMPT) and on the protonation reagent (H2O or AcOH).These results, and an IR analysis of the organochromium species generated from 7(E) or 7(Z) (A, B and C in equilibrium), suggest two mechanisms of protonolysis of the organochromium intermediates; mainly S_E2 (THF+HMPT, anhydrous AcOH) or mainly S_Ei' (THF, H2O).Some unsuccesful attempts at asymmetric induction in this reaction are reported.