New stereoselective syntheses of stereodefined 2-substituted alkyl 2-alkenoates and their applications

Stereoisomerically pure alkyl (E)-2-tributylstannyl-2-alkenoates, (E)-8, which are easily prepared by palladium-catalyzed reaction between tributylstannane and alkyl 2-alkynoates, 15, have been employed as precursors to stereodefined 2-(hetero)aryl substituted alkyl 2-alkenoates of general formula 9 as well as alkyl (E)-2-methyl-2-alkenoates, (E)-10, having very high stereoisomeric purity. One of these esters. i.e. ethyl (Z)-4-(tert-butyldimethylsilyloxy)-2-phenyl-2-butenoate, (Z)-9d, has been employed in a very simple and efficient synthesis of 3-phenyl-5(H)-2-furanone, 12, a metabolite of an hypnotic drug. On the other hand, the procedure employed to prepare esters (E)-10, which involves a configurational inversion, has been used to prepare the (S)-enantiomer of (E)-2,4-dimethyl-2-hexenoic acid, (E)-13, a caste-specific substance of male carpenter ants in the genus Camponotus, as well as 98% optically pure (S)(E)-4,6-dimethyl-4-octen-3-one, (S)(E)-14, an alarm pheromone component of ants in the genus Manica.