BENZOXADIAZOCINES, BENZOTHIADIAZOCINES AND BENZOTRIAZOCINES-IV; RING CLOSURE OF 1-PHENYL>-3-PHENYLTHIOUREAS. TETRAHYDROQUINOXALINE VS. DIHYDRO-3,1,6-BENZOTHIADIAZOCINE AND HEXAHYDRO-1,3,6-BENZOTRIAZOC
While base induced ring closure of 1-phenyl>-3-phenylthioureas 1 had furnished the corresponding type 2 dihydro-3,1,6-benzothiadiazocine derivatives rather than the isomeric hexahydro-1,3,6-ben