[3,3]-Sigmatropic rearrangement of allenic alcohols: stereoselective synthesis of 1,3-diene-2-ol sulfonates

An efficient synthetic pathway to 1,3-diene-2-ol sulfonates involving the [3,3]-sigmatropic rearrangement of allenic alcohols with sulfonic acids under mild reaction conditions is described. These products can easily undergo reduction or transition-metal catalyzed cross-coupling reactions to yield a series of stereodefined multisubstituted 1,3-dienes.

Stereoselective preparation of conjugated (Z)-1,3-enynes by dehydration reactions of allenic bromohydrins and the use of the enynes in base-mediated tandem allylation ene-carbocyclization reactions with β-ketoesters

A procedure has been developed for the concise, stereoselective synthesis of (Z)-5-bromo-4-aryl-pent-3-en-1-ynes through Sc(OTf)₃ catalyzed dehydration reactions of allenic bromohydrins. (Z)-1,3-Enynes are transformed to methylenecyclopentenes when subjected to a sequential, one-pot process involving base mediated allylation reactions with ethyl acetoacetate followed by ene-carbocyclization reactions. An unprecedented rearrangement reaction involving 1,5-acyl migration takes place when the methylenecyclopentenes are treated with acid to form highly substituted cyclopentadienes.

Synthesis of hexahydro-1H-isoindole derivatives from arylacyl bromides via homoallenic bromohydrins

A procedure has been developed for the concise synthesis of hexahydro-1H-isoindole derivatives starting from phenacyl bromides. The approach employs a sequence involving an initial indium-mediated allenylation reaction of an arylacyl bromide with propargyl bromide. This process is followed by FeBr3-mediated SN2'-type substitution reaction of the formed homoallenic bromohydrin to produce a 2,5-dibromo-4-aryl-1,3-pentadiene, which then is subjected to a sequential, one-pot N-alkylation reaction with N-allyl-N-(p-tosyl)amine and a highly diastereoselective intramolecular Diels-Alder reaction of the formed ene-diene to generate the target hexahydro-1H-isoindole.