- First Thia-Diels–Alder reactions of thiochalcones with 1,4-quinones
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Aryl and hetaryl thiochalcones react smoothly with 1,4-quinones in THF solution at 60 °C yielding the corresponding fused 4H-thiopyrans after spontaneous dehydrogenation of the initially formed [4 + 2] cycloadducts. In general, the yields of the isolated products were high. With 5-chloro-10-hydroxy-1,4-anthraquinone, the thia-Diels–Alder reaction occurred with complete regioselectivity. In the case of the reaction of vitamin K3 (menadione) with diphenylthiochalcone, the initial cycloadduct was isolated in 37% yield.
- Mlostoń, Grzegorz,Urbaniak, Katarzyna,Urbaniak, Pawe?,Marko, Anna,Linden, Anthony,Heimgartner, Heinz
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- Diastereoselective Synthesis of Anthracyclinone Precursors
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Cycloaddition of various dienes such as 1-acetoxy-1,3-butadienes 4a, b or 1-phenylethoxy-1,3-butadienes 4c-g with 1,4-anthraquinones 3 affords tetracyclic precursors of anthracyclinone.Using the chiral substituted 1,3-butadienes 4 cycloadducts with d.e. >98percent are obtained.The high stereoselectivity is explained by ? stacking.Key Words: Anthracyclinones / Diels-Alder reactions, asymmetric / 1,4-Anthraquinone / Isoprenyl ethers / 1-Phenylethanol
- Flock, Markus,Nieger, Martin,Breitmaier, Eberhard
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p. 451 - 456
(2007/10/02)
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- Chemistry of Quinones. Part 7. Synthesis of Anthracyclinone Analogues via Diels-Alder Reactions of 1,4-Anthraquinones
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Diels-Alder adducts were formed by reaction of 1,4-anthraquinone with buta-1,3-diene, with 1-acetoxy-, 1-methyl-, 2-methyl-, and 2,3-dimethyl-buta-1,3-diene, and with cyclohexa-1,3-diene.Adducts were also prepared by reaction of 9-chloro-10-hydroxy-1,4-anthraquinone with buta-1,3-diene and with 2-methylbuta-1,3-diene.Some of the linear tetracyclic adducts were transformed to 1,2,3,4-tetrahydro-1,5,12-trihydroxynaphthacene-6,11-quinone (21) and 2-acetyl-1,2,3,4-tetrahydro-2,5,12-trihydroxynaphthacene-6,11-quinone (7).The latter has been converted by other workers into 4-demethoxydaunomycinone (48) and 4-demethoxydaunomycin (8).
- Gupta, Dharmendra N.,Hodge, Philip,Khan, Naeem
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p. 689 - 696
(2007/10/02)
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