Siloxacyclopentenes as Dienophile-Linked Directing Groups in Intramolecular Diels-Alder Reactions

摘要

The synthesis and intramolecular Diels-Alder reactions of trienes 5 and 6 with a siloxacyclopentene-constrained dienophile are described. These reactions provide the primary cycloadducts 7 and 8 with high diastereoselectivity. These cycloadducts possess trans-relationships between the ring fusion proton and the adjacent C(1) alkoxy group, and can be further elaborated to alcohols 9 and 11 (via protiodesilylation), or to 10 and 12 (via Fleming-Tamao oxidation) depending on the substitutent R.