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The reaction of thebaine with 2-bromo-6-methyl-1,4-benzoquinone regioselectively afforded 6,18- endo-etheno-9-methyldihydrothebainehydroquinone. Iodination of 6,18- endo-ethenodihydrothebainehydroquinones with N-iodosuccinimide in trifluoroacetic acid was also selective, and the corresponding 1-iodo derivatives were formed. The main reaction pathway in the halogenation of 6,18- endo-ethenodihydrothebainehydroquinone with iodine chloride was chlorination of the fused hydroquinone fragment. The Sonogashira reaction of 1-iodo-6,18- endo-ethenodihydrothebainehydroquinones with trimethylsilylacetylene and subsequent desilylation gave 1-ethynyl-6,18- endo-ethenodihydrothebainehydroquinones. 1-[3-(4-R-Piperazin-1-yl)-propynyl]- and 1-{3-[2-(pyridin-3-yl)piperidin-1-yl]propynyl}-6,18- endo-ethenodihydrothebainehydroquinones were synthesized by the Mannich reaction of acetylenic derivatives of dihydrothebainehydroquinone with piperazine and anabasine in the presence of formaldehyde, catalyzed by copper(I) compounds. The reaction of 1-iodo-6,18- endo-ethenodihydrothebainehydroquinone with N-methylpiperazine and formaldehyde was accompanied by copper-catalyzed oxidative homocoupling. [ABSTRACT FROM AUTHOR]