PubMed · 4717438
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1973-07-07. Riot control agent.. https://pubmed.ncbi.nlm.nih.gov/4717438/
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[Reaction: see text]. 1,3-dinitrodibenz[b,f][1,4]oxazepin-11(10H)-one, prepared by intramolecular displacement of nitro group in N-(2-hydroxyphenyl)-2,4,6-trinitrobenzamide, reacts with O- and S-nucleophiles to yield the products of mono- or bis-substitution of the nitro groups. The nitro group in position 3 is displaced first. This observation is in contrast with earlier results for the nitro-substituted benzoannulated five-membered heterocycles. This difference in reactivity is likely due to the increased steric hindrance for peri-nitro group displacement in the case of the benzoannulated seven-membered heterocycle. N-Alkylation of the nitro-substituted dibenz[b,f][1,4]oxazepin-11(10H)-ones yields analogues of a known antidepressant drug Sintamil. The structure of the products is confirmed by NOE experiments and alternative synthesis.
Irritant incapacitants, also called riot control agents, lacrimators and tear gases, are aerosol-dispersed chemicals that produce eye, nose, mouth, skin and respiratory tract irritation. Tear gas is the common name for substances that, in low concentrations, cause pain in the eyes, flow of tears and difficulty in keeping the eyes open. Only three agents are likely to be deployed: (i) 1-chloroacetophenone (CN); (ii) 2-chlorobenzylidene malononitrile (CS); or (iii) dibenz[b,f]-1,4-oxazepine (CR). CN is the most toxic lacrimator and at high concentrations has caused corneal epithelial damage and chemosis. It has accounted for at least five deaths, which have resulted from pulmonary injury and/or asphyxia. CS is a 10-times more potent lacrimator than CN but is less systemically toxic. CR is the most potent lacrimator with the least systemic toxicity and is highly stable. CN, CS and CR cause almost instant pain in the eyes, excessive flow of tears and closure of the eyelids, and incapacitation of exposed individuals. Apart from the effects on the eyes, these agents also cause irritation in the nose and mouth, throat and airways and sometimes to the skin, particularly in moist and warm areas. In situations of massive exposure, tear gas, which is swallowed, may cause vomiting. Serious systemic toxicity is rare and occurs most frequently with CN; it is most likely to occur when these agents are used in very high concentrations within confined non-ventilated spaces. Based on the available toxicological and medical evidence, CS and CR have a large safety margin for life-threatening or irreversible toxic effects. There is no evidence that a healthy individual will experience long-term health effects from open-air exposures to CS or CR, although contamination with CR is less easy to remove.
A concise synthesis of a series of novel dibenzoxepino[4,5-d]pyrazoles was accomplished by implementation of an intramolecular Ullmann-ether reaction on o,o'-halohydroxy-4,5-diarylpyrazoles mediated by CuBr.DMS. An alternative useful approach based on the palladium-catalyzed biaryl-ether linkage formation (Buchwald-Hartwig reaction) was also successfully applied, offering limitations with regard to the steric demand of the substituents. The synthesis of the key o,o'-halohydroxy-4,5-diarylpyrazole intermediates proceeds through the construction of the heterocyclic ring by a tandem amine-exchange/heterocyclization sequence of 3-N,N-(dimethylamino)-1,2-diarylpropenones with phenylhydrazine followed by basic hydrolysis for deprotection. The enamino ketone precursors were conveniently prepared from the corresponding O-sulfonyloxy and O-benzoyloxy ortho-substituted 1,2-diarylethanones, starting from inexpensive salicylaldehyde or phenylacetic derivatives. Preliminary binding affinity experiments against peripheral and central nervous system receptors have been done with negative results.