SYNTHETIC ROUTES TO 1,4-DIFUNCTIONALIZED CYCLOHEPTENES

Two routes to 1,4-difunctionalized cycloheptenes are described. The fi rst one is based on a fluoride-induced fragmentation reaction of the b icyclic [3.2.0] heptanesilyl monosulfate 10. This compound in turn was prepared by a ketene-cyclopentene cycloaddition route. An alternative strategy took advantage of a ring-closed metathesis (RCM) reaction of the diolefin 18 with the ruthenium catalyst 21. This reaction proved to be reliable even on a larger scale and allowed the isolation of the cycloheptene 19a in reasonably good yield.