Pomeranz–Fritsch reaction

[2][3][4] The reaction below shows the acid-promoted synthesis of isoquinoline from benzaldehyde and a 2,2-dialkoxyethylamine.

[5] Various alkyl groups, e.g. methyl and ethyl groups, can be used as substituent R. In the archetypical reaction sulfuric acid was used as proton donor, but Lewis acids such as trifluoroacetic anhydride and lanthanide triflates have been used occasionally.

[1][2][4] Later, a wide range of diverse isoquinolines were successfully prepared.

[4] A possible mechanism is depicted below:[5] First the benzalaminoacetal 1 is built by the condensation of benzaldehyde and a 2,2-dialkoxyethylamine.

The Pomeranz–Fritsch reaction has general application in the preparation of isoquinoline derivatives.