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A novel methodology to accelerate annulation reactions leading to condensed selenium heterocycles was developed. The reactions of selenium dihalides with methyleugenol, allyl thymyl ether, allyl 1-naphthyl and 1-naphthyl propargyl ethers were carried out in the presence of alcohols, which considerably accelerated the annulation reactions. In solvent systems CH2Cl2/MeOH or CHCl3/MeOH, the reactions proceeded as annulation–methoxylation affording condensed methoxylated heterocycles. In the presence of isopropanol, the reactions were not accompanied by alkoxylation giving condensed halogen-containing products. The annulation reaction of selenium dihalides with 1-naphthyl propargyl ether included stereoselective anti-addition to the triple bond. The efficient selective synthesis of the first representatives of novel families of condensed selenium heterocycles with promising biological activity was developed. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]