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The transformation of saccharin into derivatives of lmidazo[1,2‐ b ] [1,2]‐benzisothiazole and benzo[g] [1,2,5]thiadiazocine
Author(s) -
Ashby John,
Griffiths D.,
Paton D.
Publication year - 1978
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570150621
Subject(s) - chemistry , isothiazole , thionyl chloride , saccharin , alkali metal , derivative (finance) , medicinal chemistry , reactivity (psychology) , ring (chemistry) , organic chemistry , chloride , medicine , alternative medicine , pathology , financial economics , economics , endocrinology
Reaction of 3‐(2‐hydroxyethylamino) benzo[ d ]isothiazole 1,1‐dioxide ( 5a ) with thionyl chloride gives a mixture of the expected chloroethyl derivative ( 5h ) and the rearranged saccharin 2‐(2‐aminoethyl)‐3‐oxo‐2,3‐dihydrobenzo[ d ]isothiazole 1,1‐dioxide hydrochloride ( 6a ). Separate treatment of the chloroethyl compound ( 5h ) with dilute alkali gives the expected cyclization product 2,3‐dihydroimidazo[1,2‐ b ] [1,2] benzisothiazole 5, 5‐dioxide ( 7a ). Acidification of the liquors of the above reaction yields the ring expanded derivative 6‐oxo‐3,4,5,6‐tetrahydro‐[2 H ]benzo[ g ][1,2,5]thiadiazocine 1,1‐dioxide ( 12f ), a representative of a new ring‐system. Treatment of the imidazo derivative ( 7a ) with concentrated hydrochloric acid again yields the N ‐substituted saccharin ( 6a ) which upon treatment with alkali also produces the thiadiazocine ( 12f ). In contrast, treatment of the imidazo compound ( 7a ) with alkali leads to attack on the sulphonamide function to give 2‐(2‐imidazolin‐2‐yl)benzenesulphonic acid ( 8 ). It is suggested that the multitude of chemical interconversions which can be induced within this series of compounds (Scheme II) can only be accounted for if two separate cyclol intermediates are invoked. Related reactions observed with variously substituted derivatives of the starting saccharin derivative ( 5a ) are discussed as are the spectral properties and chemical reactivity of the new compounds prepared.