The synthesis of a series of 5,6-diarylpyridazinones is described. Some members of this series display an antihypertensive effect in both the spontaneously hypertensive rat (SHR) model and the deoxycorticosteroid (DOCA) model of hypertension. The most potent compounds in the series have halogen substituents on the 5,6-diphenyl rings, a beta-substituted alkyl group at the 2 position of the ring, and acetyl or cyano substituent at the 4 position.

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A number of phenyl‐substituted nitrogen heterocycles and the corresponding 2,6‐diethylphenyl derivatives were examined by 13C nmr in order to verify that the heterocyclic ring system was the same in both series. The heterocyclic ring carbon shifts did not differ substantially between the phenyl and 2,6‐diethylphenyl derivatives for all systems except one, where substantial differences were also seen in the 15N chemical shifts. Acetylated derivatives were prepared to confirm the cyclization mode in this latter case.

The detection, isolation, and identification of the impurities in the technical grade of the insecticide thiofanox are described. A 13C NMR method was employed to detect impurities at about the 0.1% level or greater. The 13C spectrum of very high signal-to-noise ratio of an impurity concentrate was used to guide subsequent separation and identification work. The sensitivity and reliability of this approach are discussed. Preparative and semipreparative high performance liquid chromatography was employed to isolate 39 nonvolatile components. These were identified on the basis of spectral data and by comparisons with authentic samples which were synthesized when necessary. Some stereochemical assignments are made on the basis of NMR chemical shifts. An additional 30 volatile components were isolated and identified by vacuum distillation and gas chromatography/ mass spectrometry.

A simple and convenient synthesis of a radiolabeled antihypertensive pyridazinone was developed. The product was purified chromatographically, and the chemical and radiochemical purities of the sample were determined.