ROLE OF FLUORINE IN CYCLOCONDENSATION OF 3-ARYLIMINO-2H-INDOL-2-ONES WITH O-MERCAPTOBENZOIC ACID

The synthesis of some new fluorinated spiro-indole derivatives is repo rted. Cyclocondensation of 3-arylimino-2H-indol-2-ones, prepared by th e treatment of various fluorinated anilines with isatins, with o-merca ptobenzoic acid in acidic ethanol was investigated for the first time. A novel spiro system, -benzothiazine-2,3'-[3H-indole]-2',4(1'H,3H)-di one (4) was isolated. Further, the role of fluorine in such cycloconde nsation reactions has been studied. It was observed that 2,3,4,5,6-pen tafluorophenyl)-imino-2H-indol-2-one, 2 afforded exclusively (1,3-dihy dro-2-oxo-(2H)indolyl)]-o-mercaptobenzoic acid 5 instead of the expect ed spiro compound as obtained with mono to tetra fluorinated imino ind oles. The spiro compounds have been further subjected to methylation a nd morphomethylation.