Synthesis of Linear Tetraquinanes by [3+2] Cycloaddition, Chemoselective Allylation of 7-Ketonorbornene, and Ring-Rearrangement Metathesis as Key Steps

Abstract A nine-step synthetic sequence to linear tetraquinanes involving [3+2] cycloaddition, chemoselective allylation, and ring-rearrangement metathesis as key steps is reported. A chemoselective allylation of 7-ketonorbornene was realized for the first time by using indium powder and allyl bromide. By this method, norbornene ketones can be selectively allylated in the presence of a cyclopentanone moiety to give good yields of monoallylated Barbier-type products.