EFFECTS OF REMOTE N-(TERT-BUTOXYCARBONYL) GROUPS ON HETEROATOM DIRECTED LITHIATION AT BENZYLIC POSITIONS

Lithiation of N-BOC-2-methylphenethylamine (6) occurs exclusively at the methyl group whereas lithiation of the phenylpropyl congener (11) is less regioselective. N-BOC-phenylpropylamine (17) is efficiently lithiated at the benzylic position while N-BOC-2-methylphenylbutylamine (23) undergoes lithiation of the methyl group but with low conversion. The results are discussed from the general perspective of heteroatom-directed metalation. Several of the lithio derivatives can be converted to heterocycles, e.g., tetrahydro-3-benzazepin-2-one (10), hexahydro-3-benzazocin-2-one (16) and 3-phenylpyrrolidines (19-22).