- Synthesis of the reported structure of the bisbenzoquinone lanciaquinone, isolated from Maesa lanceolata
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(Chemical Equation Presented) Lanciaquinone, isolated from Maesa lanceolate, was originally assigned as a bisbenzoquinone with a C 14-chain linking the two quinone rings. A synthesis of the reported structure, in which the key step is a double Clalsen rearrangement, suggests that the structure of the natural product needs to be revised.
- Guillonneau, Loic,Taddei, David,Moody, Christopher J.
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supporting information; experimental part
p. 4505 - 4508
(2009/05/27)
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- PROCESS FOR PREPARATION OF ESCULETIN COMPOUNDS, ESCULETIN COMPOUNDS AND INTERMEDIATES THEREOF, AND USE OF BOTH
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An esculetin compound, an intermediate thereof, a process for manufacturing an esculetin compound, and an antifungal composition for agriculture and horticulture and an herbicide comprising an esculetin compound or an intermediate thereof are provided. The process for manufacturing an esculetin compound is a low-cost, high-yield, and industrially practicable process, and comprises the following step.A process for manufacturing an esculetin compound of the formula (2): characterized by cyclizing a trihydroxybenzaldehyde compound of the formula (1): in an aprotic polar solvent in the presence of a weak base, with acetic anhydride or the like.
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Page/Page column 14
(2010/01/31)
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- Regioselective synthesis of substituted pterocarpans and pterocarpenes. Lewis acid Ti(IV) promoted formal (3 + 2) cycloaddition reactions
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A synthesis of novel pterocarpans (8a-3, 10a-c and 11a-e) and pterocarpenes (7a-d and 9a-c) has been carried out. This method involves the Lewis acid Ti(IV) promoted formal (3 + 2) cycloaddition reaction of 2-alkoxy-1,4-benzoquinones (6a-c) with appropriately substituted 2H-chromenes (1a-b, 2a-b and 5) at -78°C.
- Murugesh,Subburaj,Trivedi
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p. 2217 - 2228
(2007/10/03)
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- Stereospecific Lewis Acid-Promoted Reactions of Styrenyl Systems with 2-Alkoxy-(6-alkyl)-1,4-benzoquinones: Scope, Limitations, and Synthetic Applications
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Titanium(IV)-promoted reactions of various (E)-1-propenylbenzenes with 2-methoxy- and 2-methoxy-6-methyl-1,4-benzoquinones produce trans 2-aryl-6-methoxy-3-(and 4-di)methyl-2,3-dihydro-5-benzofuranols (10-12), rel-(1S,6R,7R,8R)-3-methoxy-8-aryl-7-(and 1-di)methylbicyclooct-3-ene-2,5-diones (2 + 2 cycloadducts, 13-15) and/or rel-(1R,5R,6R,7R)-7-aryl-3-hydroxy-6-(and 4)-methylbicyclooct-3-ene-2,8-diones (5 + 2 cycloadducts, 16/17).In many cases, each of the three products can be obtained selectively in good yield by control of reaction conditions and/or by choice of substituents on the quinone or the propenylbenzene.The dihydrobenzofurans are formed stereoselectively, whereas the formation of the bicyclo systems are stereospecific processes.Thus, reactions of (Z)-1-propenylbenzenes afford rel-(1R,6S,7R,8R)-8-aryl-3-methoxy-7-methylbicyclooct-3-ene-2,5-diones (24, 25).No bicyclosystems are found in reactions of the (Z)-propenylbenzenes.The products all apparently result from a thermally allowed 2? + 4? (2 + 5) cycloaddition of the propenylbenzene with a 2-methoxy-4-oxo-2,5-cyclohexadienyl carbocation intermediate (26) formed by coordination of the Ti(IV) to the C-1 carbonyl oxygen of the quinone.In the cycloaddition, the aryl ring of the propenylbenzene occupies an endo position with respect to the pentadienyl carbocation moiety of 26 and the bicyclo carbocation product of the cycloaddition (28/29) either undergoes dealkylation or rearrangement to yield the observed products.Treatment of the bicylo systems with protic acid effects their rearrangement to the dihydrobenzofuranols.Reactions of 2-propenylbenzenes and arylcycloalkenes with the quinones regioselectively give dihydrobenzofuranols 43-45 and 49-54, respectively; a 2 + 2 cycloadduct is found in low yield in only one case.The 7-aryl-3-hydroxy-6-methylbicyclooct-3-ene-2,8-diones are produced exclusively in reactions of 2-((4-methoxybenzyl)oxy)-1,4-benzoquinones with various propenylbenzenes.Application of these reactions to the synthesis of (+/-)-obtusafuran, (+/-)-liliflol-B, (+/-)-kadsurenone, and (+/-) denudatin are reported.
- Engler, Thomas A.,Combrink, Keith D.,Letavic, Michael A.,Lynch, Kenneth O.,Ray, James E.
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p. 6567 - 6587
(2007/10/02)
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