Facile access to hetero-poly-functional arenes and meta-substituted arenes via two-step dimetalation and Mg/halogen-exchange protocol.

The Grignard reagent, i PrMgCl and its lithium chloride-enhanced 'turbo' derivative i PrMgCl·LiCl have been employed to investigate the single iodo/magnesium exchange reactions of the trisubstituted arenes, 2,5-diiodo- N , N -diisopropylbenzamide 1 , 1,4-diiodo-2-methoxybenzene 2 , and 1,4-diiodo-2-(trifluoromethyl)benzene 3 . These arenes themselves were initially prepared by a double ortho-, meta ' - deprotonation of N , N -diisopropylbenzamide, anisole and (trifluoromethyl)benzene respectively, using a sodium magnesiate reagent, and subsequent electrophilic quenching with iodine/THF solution. Thus, by following a combined deprotonation and magnesium/halogen exchange strategy, the simple monosubstituted arenes can be converted to trisubstituted diiodoarenes, which can ultimately be transformed into the corresponding mono-magnesiated arenes, in THF at -40°C, within seconds in good yields. The other functional group present on the di-iodoarenes helps direct the exchange reaction to the ortho position whereas subsequent addition of different electrophiles permits the preparation of hetero-poly-functional-arenes, with three different substituents in their structure. Intriguingly, if water is used as the electrophile, a new and facile route to prepare meta -substituted arenes, which cannot be easily obtained by conventional processes, is forthcoming. In contrast to directed ortho- metalation (D o M) chemistry, this reaction sequence can be thought of as InDirect meta -Metalation (ID m M).