H. Higuchi et al., SIMPLE SEPARATION OF AN ISOMERIC MIXTURE OF DIHEXYLBITHIOPHENES WITH HEAD-TO-HEAD AND HEAD-TO-TAIL ORIENTATIONS, Chemistry Letters, (12), 1995, pp. 1115-1116
The isomeric mixture of 3,3'-dialkylbithiophenes with head-to-head (H-
H) and head-to-tail (H-T) orientations was separated into each isomer
by using preferential bromination of the H-T isomer. This separartion
method proved to be useful for simultaneous preparation of the pure H-
H and H-T bithiophenes which are inaccessable by other methods.