Troublesome Alkoxythiophenes. A Highly Efficient Synthesis via Cyclizationof gamma-Keto Esters

A variety of alkoxythiophenes have been synthesized that represent ideal su bunits for the synthesis of a new class of thermotropic liquid crystals via palladium-catalyzed cross-coupling reactions and organometallic derivatiza tion. The methodology used represents the first highly efficient synthesis of alkoxythiophenes unlike previous pathways that have presented serious sy nthetic difficulties when the alkoxy chain consisted of more than four carb on atoms. The scope of the new procedure (relative to liquid crystalline in termediates) is presented and is compared and contrasted with the current l iterature.