The generation of the dianion of 3‐mercaptopyridin‐2(1H)‐thione with triethylamine in N,N‐dimethylform‐amide followed by reaction in the presence of 2‐chloronitrobenzene fails to give 1‐azathianthrene which is formed in good yield when sodium hydride was employed as the base. The principle product isolated from the reaction was instead 1,6‐diazathianthrene. Mechanistic considerations are discussed.

SUMMARY Multiple birefringent rhomboidal crystals seen on histological examination of a resected oesophagus were subsequently found to contain elemental barium and sulphur on energy dispersive x ray (EDX) analysis. Scanning electron microscopy and EDX analysis of readily available commercial barium sulphate suspensions suggested that the two forms of barium sulphate previously described in tissue sections may be a result of the method of preparation of the commerical suspension used.With increased use of barium sulphate prepared by crushing the natural compound, birefringent rhomboidal crystals should be found with increasing frequency in endoscopic biopsy samples and resected specimens.In histological sections, barium sulphate classically appears as green, finely granular material which is not birefringent.' Larger, birefringent rhomboidal crystals of barium sulphate may also occur, but these are usually in association with the classic green, granular forms.In the case described in this report, multiple rhomboidal crystals were found on histological examination of a resected oesophagus. No classic green, granular barium sulphate was seen histologically, and attention was focused on other possible sources for the rhomboidal crystals. The nature of these crystals was eventually determined by energy dispersive x ray (EDX) analysis, which showed elemental barium and sulphur, consistent with the patient having undergone several preoperative barium contrast studies. Between the time that he swallowed the ammonia solution and his oesophagectomy, the patient underwent three barium sulphate oesophageal studies. In each study the commercial brand of barium sulphate used was not recorded.After the operation the anastamosis healed without appreciable stricture formation. The patient is currently in good physical health, on a normal diet, and has been discharged for psychiatric assessment.

Treatment of 2‐pivaloyl‐1,3‐indandione with hydroxylamine leads to the formation of a pair of isomeric indenoisoxazoles, the product formed dependent upon the cyclization conditions. Under acidic conditions, 8‐t‐butylindeno[1,2‐c]isoxazol‐7‐one (5) is formed while under neutral or basic conditions, an oxime, 2, is generated which may then be cyclized under acidic conditions to give 3‐t‐butylindeno[1,2‐c]isoxazol‐4‐one (4). Although these isomeric indenoisoxazoles may be discriminated by chemical means, we were interested in developing an unequivocal method for distinguishing these and potentially other isomeric pairs by spectroscopic means. A 13C‐nmr based method for the discrimination of these isomers which is based on the utilization of chemical shift arguments and spin‐lattice relaxation data is thus presented.

The isolation of l-N,N-dimethylamino-2,3-diazaphenoxathiin and its molecular structure as determined by X-ray crystallography are described. The existence of a potential non-bonded interaction between the lone pair of electrons of the dimethylamino group nitrogen and sulfur atom are also discussed.

The reaction of 5-methoxy-3,4-dichloropyridazine with the disodium salt of o-mercaptophenol leads to the formation of l-methoxy-3,4-diazaphenoxathiin as the sole product of the reaction. The structure of the isolated product was confirmed by 13C-nmr spectroscopy, with the development of arguments to discriminate the isolated compound from 4methoxy-l,2-diazaphenoxathiin, the other product possible in this reaction. Mechanistic considerations in the formation of the isolated product are discussed.