Acetyl-2-phenylacetylene reacts with thiocarbohydrazide under mild conditions to afford exclusively N 2 -(Z-s-trans), N 3 -(Z-s-cis)bis(1-methyl-3-phenyl-2-propynylidene)carbonothioic dihydrazide in high yield (up to 92%); the structure of the compound has been confirmed by IR and NMR spectroscopy and X-ray analysis.
The reactions of thiocarbohydrazide and thiocarbohydrazones with bielectrophilic aryl ethynyl ketones give acyclic adducts due to the addition of nitrogen or sulfur atoms of the nucleophile to the acetylene bond, 1 as well as heterocyclic compounds due to double nucleophilic addition through the acetylene bond 2 or addition-cyclization at the acetylene bond and carbonyl moiety. 3 We found that 1-acetyl-2-phenylacetylene 1 reacts with thiocarbohydrazide 2 in (i) DMSO or (ii) AcOH at room temperature only through the carbonyl moiety to furnish N 2 -(Z-s-trans), N 3 -(Z-s-cis)-bis(1-methyl-3-phenyl-2-propynylidene)carbonothioic dihydrazide 3 in 76 or 92% yield, respectively (Scheme 1). Compound 3 was also prepared in system aqueous ethanol at 45-50 °C (in 56% yield).
The structure of compound 3 was determined by IR, 1 H, 13 C, 15 N NMR spectroscopy (in solution) † and X-ray analysis (in crystals). ‡ The experimental data are indicative of the same structure of 3 in solid state and in solution.
The IR spectra of diacetylenic dihydrazone 3 showed that the stretching vibrations of NH groups correspond to the double band ν NH with maxima at 3240, 3310 cm -1 (KBr) and 3265, 3320 cm -1 (CHCl 3 , c » 10 -2 -10 -4 mmol dm -3 ), respectively. The 1 H, 13 C and 15 N NMR spectra (CDCl 3 ) of dihydrazone 3 are characterised by the presence of doubled signals for all structural units of the molecule except for the carbon atom of the thiocarbonyl moiety. The analysis of 2D HSQC, HMBC ( 13 C-1 H) ( 15 N-1 H) spectra allowed us to assign signals to different N 2 and N 3 fragments in diacetylenic dihydrazone 3.
The IR and NMR spectra reflect the spatial asymmetry of two chemically equivalent moieties in compound 3, while significant difference in the spin-spin coupling constants 1 J N-H [(d 9.49 ppm,