Novel synthesis of protected methyl 4-hydroxy-1,2,3,4-tetrahydroisoquinoline-3-carboxylate via cleavage of functionalized dihydrooxazoles (oxazolines)

The protected methyl 4-hydroxy-1,2,3,4-tetrahydroisoquinoline-3-carboxylate is synthesized by two convergent routes from dimethyl-5-(2-formylphenyl)-2 -methyl-4,5-dihydrooxazole-4,4-dicarboxylate via cleavage of the oxazolyl m oiety, the starting dihydrooxazole is prepared on a large scale at 70 degre es C by 1,3-dipolar cycloaddition using a solvent-free process assisted by focused microwave technology.