The synthesis of medium-sized cyclic lactams by the intramolecular friedel-crafts cyclization of isocyanates. Formation of novel pyrazolo[3,4-c]benzolactams

A series of 4-ω-phenylalkyl substituted-1H-pyrazol-5-amines has been synthesized from the corresponding α-acetylphenylalkanenitriles and methylhydrazine. They were converted into the corresponding 5-isocyanates and cyclized under Friedel-Crafts conditions to medium-sized cyclic lactams. The reaction was shown to give the 7-, 8-, 9-, and 10-membered lactams but failed to yield the 11-membered lactam. Rings synthesized were: pyrazolo3,4-c]2]benzazepin-2(1H)-one; 10H-pyrazolo3,4-c]2]benzazocin-10-one; pyrazolo3,4-c]2]benzazonin-11(1H)-one; 12H-pyrazolo3,4-c]2]benzazocin-12-one.