METALATION OF THIOANISOLE AND THIOPHENETOLE WITH N-BUTYLLITHIUM

The metalation of thioanisole and thiophenetole with n-butyllithium in ether has been reinvestigated with careful product analysis. Thioanisole metalates initially in the ring with shift of lithium to the methyl group, probably by transmetalation, although the possibility of concurrent initial attack of the methyl group by n-butyllithium was not excluded by the data. The metalation of thiophenetole occurred at all ring positions with unexpectedly large amounts (compared with phenetole) of meta and para attack. Also unexpected were large amounts of cleavage of the sulfur-to-phenyl bond leading to phenyllithium. Only small amounts of metalation in the α-position of the ethyl group were indicated by the product composition. It is postulated that initial ring attack is followed by transmetalation of the α-position of the ethyl group, and that this species undergoes a rapid intramolecular cleavage of the sulfur-to-phenyl bond. © 1969.