3-Bromopenta-2,4-dienylsilane: a useful reagent for the preparation of [3]dendralenes and polycyclic compounds

Starting from ( -1-trimethylsilyl-3-bromopenta-2,4-diene, a lithium-bromine exchange reaction followed by addition onto carbonyl compounds provided the corresponding dienyl alcohols. A Peterson-type -elimination promoted by a catalytic amount of trimethylsilyl triflate cross-conjugated gave triene systems ([3]dendralene) which rapidly reacted with the appropriate dienophiles to yield tandem intermolecular Diels-Alder cycloadducts.