M. S. Chauhan

Carbon-13 nuclear magnetic resonance spectra of N-, O-, and S-methylated uracil and thiouracil derivatives

13C nmr chemical shifts have been recorded for a number of uracil, thiouracil, and pyrimidine derivatives. These data are discussed in relation to what is known of the lactam–lactim tautomerism in such systems and possible correlations of chemical shifts with normal aromatic substituent chemical shift parameters. The chemical shifts for the CH3 groups in simple methylated derivatives of uracil are very characteristic of the site of methylation and should prove useful as a tool for assigning structures to alkylated derivatives of this general type.

Some Reactions of Isothiazoline-3- and -5-thiones

Reactions of certain 3-bromothio-1,2–dithiolium bromides with primary amines produce isothiazoline-5-thiones. These compounds form adducts of varying stability with acetylenic reagents. Comparison of their reactivity with the isomeric isothiazoline-3-thiones indicates that while the former react rapidly to form only monoadducts, the latter react more slowly to form monoadducts which react more rapidly to form diadducts.

The preparation and properties of some thioacylmethylenethiazolines and isothiazolines

Thiazoline-2-thiones and isothiazoline-3-thiones are converted into the 2- or 3-thiophenacylidene derivatives, respectively, by reaction with phenacyl bromide, treatment with pyridine, and thionation. The former compounds react with dimethyl acetylenedicarboxylate to form mono- and diadducts as well as some decomposition products. Attempts to demonstrate valency isomerism in the 3-thiophenacylideneisothiazoline derivatives were unsuccessful.