Metallation reactions. XX. Regioselective metallation of (alkylthio)methoxybenzenes by superbases versus organolithium compounds

Article abstract of DOI:10.1016/S0040-4020(01)80413-0

(Alkylthio)methoxybenzenes have been metallated using two different metallating agents. The results show that sometimes superbases and butyllithium do not functionalize the same sites. Superbases monometallate the thiomethylic carbon of meta and para (methylthio)methoxybenzenes. The same substrates on the other hand are metallated by butyllithium in ortho to the methoxy group. One-step dimetallation performed with either superbases or butyllithium occurs at the thiomethylic carbon at the aryl carbon ortho to the methoxy group. Two consecutive one-pot monometallations of the para isomer (1c) with superbases occur at the thiomethylic carbon and at the annular carbon ortho to the methoxy group, in this order. A similar procedure with butyllithium metallates the two ortho positions to the methoxy group. Monometallation of (ethylthio) derivative (1d) yields, products substituted in ortho to the methoxy group using, either superbases or butyllithium. Dimetallation of this compound always substitutes the hydrogen ortho to the methoxy group and a thiomethylenic hydrogen.