Iridium-catalyzed consecutive and enantioselective [2+2+2] cycloaddition of tetraynes and hexaynes for the construction of an axially chiral biaryl system
A chiral iridium complex catalyzed a consecutive and enantioselective [2+2+2] cycloaddition of polyynes to give axially chiral compounds. Intermolecular reaction of tetraynes, possessing aryl groups on their termini, with protected but-2-yne-1,4-diols gave C2-symmetrical quateraryl compounds. Intramolecular reaction of hexaynes, possessing aryl or alkyl groups on their termini gave C2-symmetrical biaryl
A novel zirconium-mediated synthesis of substituted thiophene-fused acenes is described. A variety of substituents, such as alkyl, aryl, silyl, iodo, and alkynyl groups, could be introduced to the acene skeleton by this method. Moreover, the double coupling with tetraiodothiophene gave the corresponding dianthrathiophene.