Phenylacetyl isothiocyanate (1) was reacted with benzoyl hydrazine (2a) in acetonitrile to give thiosemicarbazide derivative 3 which was cyclized by polyphosphoric acid to give 1,2,4-triazoline-5-thione derivative 4. Treatment of 1 with thiosemicarbazide (2b) yielded another 1,2,4-triazoline-5-thione derivative 5. Similar treatment of 1 with phenyl hydrazine (2c) in acetonitrile gave a differently substituted 1,2,4-triazoline-5-thione derivative 6 in one pot-reaction. On the other hand, when the reaction was carried out in acetone, a mixture of 6 and thiadiazolidine derivative 7 was obtained. However, reaction of 1 with hydrazine hydrate (2d) gave hydrazine derivative 8. Reaction of isothiocyanate 1 with anthranilic acid (9) gave benzo [d] [1,3,6]oxazin-1-one derivative 10. Treatment of 1 with 2-aminothiophenol (11a), 2-aminophenol (11b) or o-phenylenediamine (11c) produced benzothiazole derivative 12a, benzoxazole derivative 12b and benzimidazole derivative 12c, respectively. The structures of all the products were confirmed by micro-analytical and spectral data.

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A series of 5,5‐diarylhydantoin (Dilantin) 3, 4, and 7, imidazole 1, 2, 5, 6, 8, and 9, thiazole 10–12, triazinthione 13, 15, 16, and 17, and thiadiazine 14 derivatives, containing diverse hydrophobic groups, were green synthesized through one‐pot stepwise reaction of aromatic aldehydes, vitamin B1, and nitrogen nucleophiles, for example, urea, thiourea, and thiosemicarbazide using grinding technique as well as conventional thermal methods. Such synthesized compounds have potent insecticidal activities; for example, compounds 4, 6, and 17 exhibited the highest insecticidal activity against both Plutella xylostella and Helicoverpa armigera with minimum inhibitory concentration values at 500 μg/mL and LD50 activities at 50 μg/mL. The density functional theory was then applied to explore the structural and electronic characteristics of these compounds. All the synthesized compounds have been characterized based on their elemental analyses and spectral data.

The reaction of lauroyl isothiocyanate and 2-amino-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carbonitrile was used to synthesize the title compound 2. Compound 2 could serve as the main building block in the synthesis of many target heterocyclic systems. Various fused pyrimidines were synthesized in the reactions of compound 2 with sodium ethoxide, hydrazine hydrate, phenyl hydrazine, ethyl carbazate, thiourea, and/ or 2-aminothiophenol. The structures of the synthesized compounds were confirmed by microanalytical and spectral data.Key words lauroyl isothiocyanate; pyrimidine derivative; fused system; 2-amino-4,5,6,7-tetrahydrobenzo[b]-thiophene-3-carbonitrile Pyrimidine and fused heterocyclic pyrimidine derivatives have received significant attention over the past few years owing to their therapeutic and pharmacological properties.

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