METALATION REACTIONS .14. REGIOSPECIFIC PREPARATION OF POLYSUBSTITUTED BENZENES VIA MONO-LITHIATION OR DI-LITHIATION REACTIONS OF AROMATIC THIOETHERS

The preparation of polyfunctionalized aromatic thioethers either by one-step dilithiation or by two successive one-flask monometalation reactions is described. By acting on 1 two equal or different electrophiles one on the thiomethyl group and one in the ortho-position with respect to it are introduced; by acting on 11 and on 35 the substitution involves the thiomethyl carbon atom and that in the ortho-position with respect to the alkoxy group. In the case of the homologous isopropylthio (23) the substitution involves the two aryl carbon atoms in the ortho-position to both functions. In the case of the p-disubstituted isomers (49, 59) analogous behaviour to ortho isomers in one-step metalation reaction is observed, while the two hydrogen atoms in the ortho-positions to the methoxy group are substituted when two successive monometalations are employed. The metalation of 40 results low selective. The behaviour of 79 and 93 is analogous to 1, while 72, 88 and 96 undergo only one-step monometalation reactions. © 1990.