BROMINATION DEUTERATION AND LITHIATION OF DITHIENYLS

Reaction of 2,2′-dithienyl (1), 2,3′-dithienyl (2), and 3,3′-dithienyl (3) with 2 equiv of NBS in chloroformacetic acid leads to the formation in virtually quantitative yield of 5,5′-dibromo-2,2′-dithienyl (4), 2′,5-dibromo-2,3′-dithienyl (5) and 2,2′-dibromo-3,3′-dithienyl (7), respectively. Reaction of 2 and 3 with excess NBS in CCl4 for long periods leads to formation of 2′,5,5′-tribromo-2,3′-dithienyl (6) and 2,2′,5,5′-tetrabromo-3,3′-dithienyl (8), respectively. Reduction of the bromodithienyls to the respective deuterio compounds is described. The nmr spectra of 1 and 3 have been analyzed and that of 2 has been partially solved. Exchange in refluxing deuterioacetic acid with 1 leads to exchange at the 5,5 positions, with 2 to exchange at the 2′ and 5 positions, and with 3 to exchange at the 2,2′ positions. Exchange reactions with n-butyllithium have been carried out with 1,2, and 3; all α positions undergo exchange. Results of electrophilic substitution are compared with predictions obtained from extended Pariser-Parr-Pople calculations. © 1969, American Chemical Society. All rights reserved.