Ortho-Lithiated Tertiary Benzamides. Chain Extension via o-Toluamide Anion and General Synthesis of Isocoumarins Including Hydrangenol and Phyllodulcin

Article abstract of DOI:10.1021/jo00179a002

Lithiation of N,N-diethyl-2-methylbenzamide (2a) followed by condensation with aromatic aldehydes and basic hydrolysis leads to 3-aryl-3,4-dihydroisocoumarins 4 in modest overall yields.Adoption of this methodology to N,N-dimethyl-2-methyl-6-methoxybenzamide (7b) provides isocoumarins 9a and 9b which by selective demethylation procedures yields hydrangenol (10a) and phyllodulcin (10c), naturally occurring isocoumarins of pharmacological interest.A one-pot, abbreviated procedure for the preparation of both 9a and 9b starting with N,N-Dimethyl-2-methoxybenzamide (6c) is also described.