Synthese yon 2,6-Diencarbonsäuren Vorläufige Mitteilung

Through sequential Claisen- and Cope rearrangements the chainlengthening of allylic alcohols by one isoprene unit was achieved. Treatment of (E)-1a first with lithium N-cyclohexyl-N-isopropylamide at ?70°, followed by trimethylsilylchloride and warming up to room temperature yielded after work-up 3a (R = H), which rearranged at 156° in high yield to (E/Z)-4a. An analogous reaction sequence transformed 6 to 8. Choosing lithium N-methylanilide as a base (E/Z)-9 was selectively rearranged to 12, which was converted to the Cecropia juvenile hormone precursor (E/Z)-4b.