Regio- and Chemoselective Synthesis of Fully Substituted Thiophenes

Abstract
A full functionalization of all four positions of the thiophene ring was achieved. Starting from readily available 2,5-dichlorothiophene, successive magnesiations of the 3- and 4-positions using TMPMgCl·LiCl furnish, after trapping with various electrophiles, 3,4-difunctionalized dichlorothiophenes. Subsequent dechlorination and metalation or magnesium insertion into the C−Cl bond provides fully functionalized thiophenes in high yields. An application to the synthesis of a thiophene analogue of Atorvastatin (Lipitor) is reported.