A New Route to [g]-Fused 5-Methyl-1-functionalized Isoquinolines

Abstract
2-(3-Lithio-2-methoxy-4-pyridyl)-4,4-dimethyl-2-oxazoline (8) was condensed with aromatic aldehydes. Subsequent hydrolysis gave the corresponding lactones 10. Reduction by ammoniacal zinc or calalytic hydrogenation of these compounds over palladium yielded 3-arylmethyl-2-pyridone-4-carboxylic acids 11 which were transformed into 3-arylmethy1-4-acetyl-2-pyridones 12 by methyllithium. Acidic ring closure then easily led to (g)-fused 5-methyl-2H-isoquinoline-1-ones via a convergent pathway. This method is more rapid and convenient than former procedures reported for the synthesis of (g)-fused 5-methyl-1-functonalized isoquinolines.

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