Imidoyllithiums: Masked acyllithium reagents

The reaction of chloroimines 1 with an excess of lithium powder and a catalytic amount of naphthalene (4 mol %) in THF at -78 degrees C leads to the corresponding imidoyllithium intermediates 2, which by treatment with different electrophiles [(PrCHO)-C-i, (BuCHO)-C-t, n-C5H11CHO,, PhCHO, Et2CO, (CH2)(5)CO, EtOCOCl, MeOCSCl, n-C7H15CON(Me)OMe] at -78 to 20 degrees C and final hydrolysis with water affords functionalysed imines 3. For starting material la is necessary to filter off the excess of lithium at the end of the lithiation step in order to get compounds 3, without filtration amines 4 are the reaction products isolated. Hydrolysis of compounds 3 either during chromatographic purification or by acidic hydrolysis (2 N HCl, THF) gives the expected functionalised ketones 5. (C) 1997 Elsevier Science Ltd.