Martin S. Gibson

Synthetic routes to 1,5-dihydro-5-oxo-4,1-benzoxazepines and to 5-oxooxazolo[3,2-a]quinolines

Abstract The literature concerning phenacyl anthranilate, N- phenacylanthranilic acid and phenacyl N-phenacylanthranilate is clarified. Phenacyl anthranilate is dehydrated to 1,5-dihydro-5-oxo-2-pheny 1-4,1-benzoxazepine by treatment with phosphoryl chloride; other examples of this reaction are described. A preparation of 4-methyl-5-oxo-2-phenyloxazolo[3,2-a]quinoline from N-phenacylanthranilic acid and propionic anhydride is reported.

Acylation of N′-arylbenzothiohydrazides and of their N′-acyl-derivatives; 2-acylalkylidene-3-aryl-5-phenyl-2H-1,3,4-thiadiazolenes and related compounds

Reactions of N′-arylbenzothiohydrazides and of their N-acyl-derivatives with carboxylic anhydrides under various sets of conditions are shown to lead to 2-acylalkylidene-3-aryl-5-phenyl-2H-1,3,4-thiadiazolenes. The probable mechanism of formation of these compounds via the corresponding 2-alkylidenethiadiazolene as intermediate is discussed.

DIMERIC AND MONOMERIC METHINE BASES IN THE 1,3,4-THIADIAZOLE SERIES

Abstract Treatment of 2-alkyl-3,5-diaryl-1,3,4-thiadiazolium perchlorates 1 with triethylamine leads to monomeric or dimeric methine bases, 2 or 3, depending on the extent of substitution (—CH2R) within the alkyl group; 1,3,4-thiadiazolium salts 7 bearing a 2-isopropyl substitutent give monomeric methine bases 8. Hydrolysis of methine bases 2 and 8 gives N′-alkanoyl-N′-arylbenzothiohydrazides 4 and 6 respectively. The first examples of isolation of monomeric methine bases 2 and their conversion to dimeric methine bases 3 in this series are provided where R = Cl.

Cleavage of halogenobenzophenones by potassamide in ammonia; new routes to xanthen- and thioxanthen-9-ones

Treatment with potassamide in ammonia cleaved 2-chloro-4′-methoxy- and -4′-methylthio-benzophenones to give 4-methoxy- and 4-methylthio-benzoic acids respectively, but 2-chloro-4′-hydroxybenzophenone was largely unchanged. Similar treatment of 2′-fluoro-2-hydroxy-5-methylbenzophenone gave mainly 2-methyl-xanthen-9-one; the 2′-chloro- and 2′-bromo-analogues gave the xanthenone and the corresponding 2′-aminobenzophenone. 3′-Fluoro-2-hydroxy-5-methylbenzophenone was largely unchanged under these conditions, but the 3′-chloro- and 3′-bromo-analogues gave 2-methylxanthen-9-one and the corresponding 3′-aminobenzophenone. 2-Methylthioxanthen-9-one was prepared by two routes: (i) from 2-chlorobenzoyl chloride, 4-methylthiotoluene, and aluminium chloride; and (ii) from 3′-chloro-5-methyl-2-methylthiobenzophenone and potassamide in ammonia.

Synthesis of 1H-4,1,2-benzothiadiazines from substituted N-acetyl-N-aryl-N′-thioaroylhydrazines

Treatment of N-acetyl-N-aryl-N′-thioaroylhydrazines, in which the N-aryl group is 2,4-disubstituted, with triethylamine in refluxing acetonitrile gives 6-substituted 1-acetyl-3-aryl-1H-4,1,2-benzothiadiazines in cases where the displaceable 2-substituent is bromine, fluorine, or iodine and the 4-substituent is electron-attracting; the synthesis fails when the 2-substituent is chlorine.

Synthesis of 10-benzoyl-9-acridone and 9-acridone from 2,2′- and 2,3′-disubstituted benzophenones

Procedures are described for preparation of 10-benzoyl-9-acridone from 2-benzamido-2′- and -3′-chlorobenzophenones, and of 9-acridone from 2-amino-2′- and -3′-chlorobenzophenones.

Reaction of an Aryl Thiocyanate with p-Nitrothiophenoxide Ion and with Thioacetate Ion; Consequences of Nucleophilic Displacement at Sulfur

Reaction of p-acetamidophenyl thiocyanate (Ar1SCN) with p-nitrothiophenol (Ar2SH) in presence of triethylamine gives the diaryl disulfides Ar1SSAr1, Ar1SSAr2, and Ar2SSAr2. Reaction of Ar1SCN with ...

Cyclization of Some 2,3,5,6-Tetrafluorophenylhydrazine Derivatives. Use of Nuclear Overhauser Effect Measurements in Structural Assignment

Treatment of N-(2,3,5,6-tetrafluorophenyl)-N′-thiobenzoylhydrazine and of N-benzoyl-N′-(2,3,5,6-tetrafluorophenyl)hydrazine with acetic anhydride and triethylamine proceed without rearrangement to ...

Routes to 3-aryl-5-phenyl-2-thioacylmethylene-2H-1,3,4-thiadiazolenes

Prospective routes to the above compounds include reaction of an N′-arylbenzothiohydrazide or of its N′-acetyl derivative with thioacetic acid, when the thioacyl and acyl derivatives are formed, as well as by reaction of the 2-acylmethylene-3-aryl-5-phenyl-2H-1,3,4-thiadiazolenes with phosphorus pentasulphide. The 1H n.m.r. and mass spectra of these compounds are discussed.

Substituent effects in synthesis of 4H-1,3,4-benzothiadiazines from hydrazonyl halides and thioacetate ion

The reactions of a number of new hydrazonyl halides, mainly of the type PhCBr:N·NH·C6H3BrZ(2,4-), with potassium thioacetate in boiling acetonitrile have been examined. 4-Acetyl-2-phenyl-7-Z-4H-1,3,4-benzothiadiazines were isolated where Z = CN or CF3, but apart from these and previously reported cases (Z = halogen), the synthesis seems not to be generally extendable to other substituents Z. Also described are 4-acetyl-2-phenyl-4H-1,3,4-benzothiadiazine (from PhCCl:NNHC6H4F-o) and 4-acetyl-9-bromo-2-phenyl-4H-naphtho[1,2-e][1,3,4]thiadiazine [from PhCBr:N·NH·C10H5Br2(2,4-)].