Transmetalation and Reverse Transmetalation on Ortho-Activated Aromatic Compounds: A Direct Route to o,o'-Disubstituted Benzenes

Article abstract of DOI:10.1021/jo00247a013

Mercury Substitution ortho to appropriately activated benzenes was achieved by using the reagent lithium tetramethylpiperidide (LiTMP)/ mercuric chloride.LiTMP provides for lithiation ortho to the activating group; HgCl2 functions as an in situ trap effecting mercury-for-lithium transmetalation.Ortho, ortho'-dimercuration was also observed; this occurs by iteration of the transmetalation process.The effects of major variables on these reactions were studied by using primarily N,N-diethylbenzamide as the activated substrate.Isopropyl benzoate, 2-phenyl-4,4-dimethyloxazoline, etc. were found to behave similarly.The mercurated aromatics could be converted to the corresponding haloaromatics in excellent yield, providing, for example, a good synthesis of o,o'-diiodo-N,N-diethylbenzamide, otherwise difficultly accessible.Reverse transmetalation methodology was employed to prepare o,o'-dilithiated-N,N-diethylbenzamide, which was characterized by its reactions with electrophiles.