Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Patent
1999-06-18
2000-03-21
Stockton, Laura L.
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C07D27504
Patent
active
060404523
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a process for making 1,2-Benzisothiazolin-3-ones (hereinafter BIT) by cyclising a bisamide precursor under alkaline conditions using oxygen or an oxygen-release compound in the presence of a nitrogen, suphur or phosphorus nucleophile.
EP 187,349 discloses a process for making BIT by disproportionation and cyclisation of 2,2'-dithiobenzamide under alkaline conditions in the presence of oxygen or an oxygen-release compound.
It has now been found that the reaction rate may be significantly increased by carrying out the disproportionation and cyclisation in the presence of a nitrogen, sulphur or phosphorus nucleophile. In many instances the yield of the BIT is also significantly increased.
According to the invention there is provided a process for making a BIT of formula ##STR1## wherein R is hydrogen, aryl, aralkyl, cycloalkyl or C.sub.1-20 -alkyl; formula 2 ##STR2## wherein q is 0-3 presence of a nitrogen, sulphur or phosphorus nucleophile.
When R is aryl it is preferably phenyl.
When R is aralkyl it is preferably benzyl or 2-phenylethyl.
When R is cycloalkyl it preferably contains not greater than 10 and especially not greater than 8 carbon atoms. Examples of cycloalkyl groups are cyclopropyl and cyclohexyl.
When R is C.sub.1-20 -alkyl, it may be linear or branched and is preferably C.sub.1-12 - and especially C.sub.1-10 -alkyl. Examples of these alkyl groups are methyl, ethyl, isopropyl, n-butyl, tert butyl, 2-methylbutyl, 2-ethylbutyl, 2-ethylhexyl, i-amyl, i-hexyl, n-hexyl and n-octyl.
Halogen is bromine, fluorine and especially chorine.
When present, the substituent X is located preferably in the 5- or 6-position of the BIT molecule and especially in the 6-position.
It is preferred, however, that n is zero.
The salts of BIT of formula 1 may be those of an inorganic or organic acid such as acetic, propionic, sulphuric, phosphoric or hydrochloric acid. However, when R is hydrogen, the BIT may also form a salt with a cation such as an ammonium or alkali metal cation. Preferred alkali metal cations are those obtainable from the alkali metal hydroxides. Preferred alkali metals are lithium, potassium and especially sodium.
The bisamide of formula 2 is preferably a 2,2'-dithiobenzamide (q is zero) but may include higher sulphur analogues (q is 1 or more) including mixtures thereof. It is preferred, however, that q is zero.
The process according to the invention has been found especially useful for making 1,2-benzisothiazolin-3-one itself (R is H).
The nitrogen, sulphur or phosphorus nucleophile may be any organic compound (including ammonia) which contains a lone pair of electrons on a nitrogen, sulphur or phosphorus atom and which is substantially inert as far as the bisamide and BIT are concerned. These nitrogen, sulphur and phosphorus nucleophiles include hard, borderline and soft Lewis Acids and Bases as set forth in "Mechanism and Theory in Organic Chemistry" (3.sup.rd Edition) by T. H. Lowry and K. S. Schueller, Harper and Row, New York, 1987 on pages 318 to 322, particularly the bases and especially those detailed in Table 3.21.
Preferred nitrogen nucleophiles are ammonia, primary, secondary and particularly tertiary amines, amides, pyridines and quinolines. Preferred amines are those containing C.sub.1-12 -alkyl groups, more preferably C.sub.1-8 -alkyl groups and especially C.sub.1-4 -alkyl groups. Examples of such amines are n-butylamine, 2-ethylbutylamine, 2-ethylhexylamine, trimethylamine and triethylamine. Especially preferred amides are the C.sub.1-4 alkyl amides of C.sub.1-4 -fatty acids such as dimethylformamide and dimethylacetamide. Pyridine nucleophiles include pyridine itself and substituted pyridines, especially those substituted by amino or C.sub.1-4 -substituted amino groups such as 4-dimethylaminopyridine.
Preferred sulphur nucelophiles are organic compounds containing a thione group and especially thioureas. The thiourea may be substituted by phenyl, chlorophenyl, C.sub.1-4 -alkyl or C.sub.1-4 -alkoxy groups. Preferably, the thiourea is unsubstituted.
Preferred
REFERENCES:
patent: 3012039 (1961-12-01), Morley
patent: 4195023 (1980-03-01), Mulvey et al.
patent: 4736040 (1988-04-01), Tonne et al.
Cox Brian Geoffrey
Gray Thomas
Stockton Laura L.
Zeneca Limited
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