Deprotonative metalation of aromatic compounds using mixed lithium-iron combinations.

International audienceNitrogen heterocycles such as 2-methoxypyridine and anisole and thiophene were regioselectively metalated by an iron complex [putatively LiFe(TMP)3; TMP = 2,2,6,6-tetramethyl-1-piperidinyl] generated from FeCl3, FeBr3, FeBr2, FeCl2, or FeI2, butyllithium, and 2,2,6,6-tetramethylpiperidine; addn. of electrophiles such as pivalaldehyde or iodine yielded alkylation or addn. compds. such as α-tert-butyl-2-methoxy-3-pyridinemethanol in addn. to dimerization byproducts. The origin of dimer formation was not detd., although mechanisms for their formation were suggested; the dependence of byproduct formation on the electrophile and on the metalated component were discussed. In particular, aldehydes gave low yields of dimerization products while other electrophiles gave dimerization byproducts in 15-41% yields; metalation of anisole and reaction with iodine gave only 2-iodoanisole and no dimerization byproduct. [on SciFinder(R)