On the reaction of 2-[(4-cyano-5,6,7,8-tetrahydroisoquinolin-3-yl)oxy]acetamides with bases: 1-amino-6,7,8,9-tetrahydrofuro[2,3-c]isoquinoline-2-carboxamides and 3-amino-4-cyano-5,6,7,8-tetrahydroisoquinolines via a Smiles-type rearrangement