- Keto ethers. IV. Products formed on reaction of dihydro-2,2,5,5-tetramethyl-3(2H)-furanone with strong acids
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Reaction of tetrahydro-2,2,5,5-tetramethyl-3(2H)-furanone (1) with 96 or ca. 100percent sulfuric acid or hot polyphosphoric acid followed by aqueous quenching gave the following products: 2-hydroxy-2,5-dimethyl-4-hexen-3-one (3), 2,4,4-trimethyl-2-cyclopenten-1-one (7), 3,5,5-trimethyl-2-cyclopenten-1-one (8), tetrahydro-2,3,5,5-tetramethylfuran-2,3-diol (11), 2,5-dihydro-3,5,5-trimethyl-2-methylenefuran (17) and its dimer 20, 2,5-dihydro-2,3,5,5-tetramethyl-2-furanol (18), 4-hydroxy-2,4-dimethyl-2-pentenoic acid γ-lactone (22), 2,3,5-trimethyl-2-cyclopenten-1-one (23), and tetramethylfuran (25).In 96percent sulfuric acid the products arise by ring opening, ring opening followed by reclosure to carbocyclic products, methyl migration from C-2 to C-3 to give rearranged furan derivatives, and oxidation.In ca. 100percent sulfuric acid or hot polyphosphoric acid further methyl migrations can occur to give 23 and 25.
- Yates, Peter,Burke, Patrick Michael
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p. 1695 - 1704
(2007/10/02)
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- Regiocontrolled Formation of 4,5-Dihydro-3(2H)-furanones from 2-Butyne-1,4-diol Derivatives. Synthesis of Bullatenone and Geiparvarin
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Two new methods for selective hydration of 1,1,4-trisubstituted 2-butyne-1,4-diols (1) to give 4,5-dihydro-3(2H)-furanone derivatives are reported.The first involves selective monoacetylation of the less hindered hydroxyl group of 1 followed by Ag(I)-cata
- Saimoto, Hiroyuki,Hiyama, Tamejiro,Nozaki, Hitosi
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p. 3078 - 3087
(2007/10/02)
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- Solvation effects on stereochemistry of reduction of 3,3,5-trimethylcyclohexanone with lithium aluminum tri-t-butoxyhydride
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Specific solvation effects on stereoselectivity in the reduction of a cyclohexanone by lithium aluminum tri-t-butoxyhydride have been studied by adding measured quantities of diethyl ether, tetrahydrofuran (THF) and methyl-substituted tetrahydrofurans to benzene solvent, and various amounts of THF to diethyl ether solvent. A steric hindrance effect in the case of bulky addends was observed, and a significant increase in stereoselectivity for less bulky addends was found. The results have been explained in terms of complexing, or steric hindrance to complexing, of the lithium cation.
- Haubenstock,Hong
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p. 2445 - 2447
(2007/10/07)
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