A one-pot synthesis of tetrahydroisoquinolin-4-ols via a novel acid-catalyzed rearrangement of 5-aryloxazolidines

Benzaldehydes with electron-donating substituents react smoothly with a nonstabilized azomethine ylide derived from sarcosine and formaldehyde to form 5-aryloxazolidines as intermediates, which undergo rearrangement into 2-methyl-1,2,3,4-tetrahydroisoquinolin-4-ols in high yields by simple heating with hydrochloric acid. This one-pot synthesis of tetrahydroisoquinolines can be considered as a formal [3+3] cycloaddition of the azomethine ylide to the aromatic aldehyde.