A novel methodology for accelerating the annulation was developed based on the reactions of selenium dihalides in the presence of alcohols.

The electronic and geometric structural changes of acetone upon protonation are studied by 3C NMR spectroscopy and by molecular orbital (MO) calculations using the LORG (local orbital/local origin) method to calculate chemical shieldings and the CLOPPA (contributions for localized orbitals within the polarised propagator approach) analysis of the J coupling constants. In protonated acetone the 13C NMR spectrum has been resolved and two different methyl resonances (1.2 ppm apart) have been assigned. The one-bond C-C coupling constants

It has been found that both eugenol and isoeugenol derivatives reacted with 2-pyridinesulfenyl and 2-pyridineselenenyl halides in a regioselective mode affording products with opposite regiochemistry. Synthesis of new families of 2H,3H-[1,3]thia- and -selenazolo[3,2-a]pyridin-4-ium heterocycles has been developed by annulation reactions of 2-pyridinechalcogenyl halides with natural compounds (eugenol, isoeugenol, methyl eugenol, methyl isoeugenol, acetyl eugenol, trans-anethole) and their structural analogs. The influence of the substrate structure and the nature of halogen on the product yields are studied. The 2-pyridinesulfenyl and 2-pyridineselenenyl chlorides are more efficient reagents compared to corresponding bromides. The obtained condensed heterocycles are novel water-soluble functionalized compounds with promising biological activity.