Ethylation of 2-Alkenyltetrahydrofurans and 2-Alkenyltetrahydropyrans Catalyzed by Titaniun(IV) Isoprpopoxide. Supplement to the Synthesis of Pheromones of Lesser Plum Worm and Tea Leaf Roller Moth

Abstract

Reaction of 2-vinyltetrahydrofuran and 2-vinyltetrahydropyran with ethylmagnesium bromude in the presence ot titanium(IV) isopropoxide afforded in moderate selectivity trans-4-octen-1-ol and trans-5-nonen-1-ol respectively. Best yields and high stereochemical purity of products were obtained in ethylation under these conditions of 2-(cis-1-propenyl)tetrahydrofuran, 2-(cis-1-proprnyl)- and 2-(trans-1-propenyl)tetrahydropyran. It is assumed that the key organometallic intermediate formed was diisopropoxytitanacycloprpopane, and direction of its addition to the doubel bond governed the streochemistry of the resulting product. The obtained trans-4-octen-1-ol and trans-7-methyl-5-nonen-1-ol were applied as initial products in the synthesis of sex pheromones of lesser plum worm (Grafolita funebrana) and tea leaf roller moth (Adoxophyes sp).