METALATION REACTIONS .20. REGIOSELECTIVE METALATION OF (ALKYLTHIO) METHOXYBENZENES BY SUPERBASES VERSUS ORGANOLITHIUM COMPOUNDS

(Alkylthio)methoxybenzenes have been metallated using two different me tallating agents. The results show that sometimes superbases and butyl lithium 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 i n ortho to the methoxy group. One-step dimetallation performed with ei ther superbases or butyllithium occurs at the thiomethylic carbon and 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 gr oup, in this order. A similar procedure with butyllithium metallates t he two ortho positions to the methoxy group. Monometallation of (ethyl thio) derivative (1d) yields products substituted in ortho to the meth oxy group using either superbases or butyllithium. Dimetallation of th is compound always substitutes the hydrogen ortho to the methoxy group and a thiomethylenic hydrogen.