Efficient synthesis of vinyl ethers of spiroquinol ketals and their high-yield photochemical oxygen-to-carbon [1,3]-shift to spiro-fused 2,5-cyclohexadienones

Swenton, John S.; Callinan, A.; Wang, Shaopeng

doi:10.1021/jo00027a017

Cited by 30 publications

(5 citation statements)

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“…To a round-bottom flask under argon were added 1-(6-bromobenzo[ d ][1,3]dioxol-5-yl)ethanol (2.90 g, 11.83 mmol), DBU (0.18 mL, 1.18 mmol), and DCM (39 mL). The reaction mixture was stirred at room temperature for 15 min and then cooled to 0 °C in an ice/water bath.…”

Section: Methodsmentioning

confidence: 99%

Alkylation of Sulfonamides with Trichloroacetimidates under Thermal Conditions

Wallach

Chisholm

2016

J. Org. Chem.

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An intermolecular alkylation of sulfonamides with trichloroacetimidates is reported. This transformation does not require an exogenous acid, base, or transition metal catalyst, instead the addition occurs in refluxing toluene without additives. The sulfonamide alkylation partner appears to be only limited by sterics, with unsubstituted sulfonamides providing better yields than more encumbered N-alkyl sulfonamides. The trichloroacetimidate alkylating agent must be a stable cation precursor for the substitution reaction to proceed under these conditions. Graphical abstractThe sulfonamide functional group has played an important role in the development of numerous pharmaceuticals. While best known as antibiotics, sulfonamide scaffolds provide a diverse range of biological activity including antitumor, antiviral, diuretic, antiinflammatory and anti-hypertensive properties. 1 Summaries of the top selling pharmaceuticals clearly demonstrate that sulfonamides are well represented in these valuable structures. 2 Data on recently approved pharmaceuticals indicate that sulfonamides continue to be popular in drug discovery, 3 with recent publications in the medicinal chemistry field corroborating that the investigation of sulfonamide-containing structures is ongoing. 4 Sulfonamides also have proven useful in agricultural and insecticidal applications. 5

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Section: Methodsmentioning

confidence: 99%

Alkylation of Sulfonamides with Trichloroacetimidates under Thermal Conditions

Wallach

Chisholm

2016

J. Org. Chem.

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“…The solution was filtered and concentrated in vacuo. Extractive workup with Et 2 O (40 mL) gave an oily tan solid which was chromatographed on Florisil [2 × 15 cm column, PE (200 mL), 5% EtOAc/PE (100 mL), 10% EtOAc (250 mL) as eluants] to give the dione 26 (0.058 g, 72%) identical with the known compound 17a…”

Section: Methodsmentioning

confidence: 99%

“…If this effect were general, the requirement of having an α-substituent on the double bond for a good yield of spiro dienone would be circumvented. With general routes to 4-(2-alkenylaryl)phenols now available, this chemistry complements photochemical17a and thermal routes 17b to these spiro dieneone ring systems.…”

mentioning

confidence: 99%

Intramolecular Anodic Carbon−Carbon Bond Formation from Oxidized Phenol Intermediates. Effect of Oxygenated Substituents on the Yields of Spiro Dienones in Electrochemical and Iodobenzene Diacetate Oxidations

et al. 1996

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The single-cell, constant-current anodic oxidation of a series of 4-(2-alkenylaryl)phenols was studied in which the aryl substituents were 2-vinyl-4,5-dimethoxy, 6a; 2-propenyl-4,5-dimethoxy, 9a; 2-vinyl-4,5-methylenedioxy, 6b; 2-propenyl-4,5-methylenedioxy, 9b; 2-vinyl-4-methoxy, 6c; 2-propenyl-4-methoxy, 9c; 2-vinyl-5-methoxy, 6d; and 2-propenyl-5-methoxy, 9d. Two compounds having methoxyl groups on the phenolic ring were also studied: 4-(2‘-propenylphenyl)-2-methoxyphenol, 9e, and 4-(2‘-propenylphenyl)-3-methoxyphenol, 9f. A novel synthetic route to the methoxy compounds 6c, 9c, 6d, and 9d was developed. This involved as a key step the MAD, bis(2,6-di-tert-butyl-4-methylphenoxide)methylaluminum, mediated addition of organolithium and Grignard reagents to functionalize quinol ether derivatives. Anodic oxidation of compounds 6a, 9a, 9b, 6c, 9c, and 9d gave good yields of spiro dienones arising from trapping of the phenoxonium ion by the alkenyl side chain followed by reaction of the resulting cation with methanol. The products from the electrochemical oxidation of these 4-(2‘-alkenylaryl)phenols were compared with those obtained from the iodobenzene diacetate oxidations. In general, the compounds that gave good yields of spiro dienones from electrochemical oxidation gave good yields from iodobenzene diacetate oxidations. However, there were two cases in which the results of the two oxidations did not parallel each other. Whereas anodic oxidation of 9f gave a low yield of spiro dienone, the iodobenzene diacetate route gave a 74% yield of this product. In the case of 9d, the opposite effect was noted: the electrochemical route gave a higher yield than did the iodobenzene diacetate oxidation.

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“…Swenton has extensively investigated the 1,2-addition of organolithium reagents to dialkoxy p -benzoquinone ketals, such as 7 , , and monosilyloxy ketals, such as 294 (Figure ) . Compound 294 is prepared by selective hydrolysis of the corresponding bis-ketal formed by electrolysis of a 4-trialkylsiloxyanisole in methanol .…”

Section: 2 Reactionsmentioning

confidence: 99%

Cyclohexadienone Ketals and Quinols: Four Building Blocks Potentially Useful for Enantioselective Synthesis

2004

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Efficient synthesis of vinyl ethers of spiroquinol ketals and their high-yield photochemical oxygen-to-carbon [1,3]-shift to spiro-fused 2,5-cyclohexadienones

Abstract: IN 47415, is thanked for the X-ray structure determination of compounds 14 and 36.

Cited by 30 publications

References 0 publications

Alkylation of Sulfonamides with Trichloroacetimidates under Thermal Conditions

Alkylation of Sulfonamides with Trichloroacetimidates under Thermal Conditions

Intramolecular Anodic Carbon−Carbon Bond Formation from Oxidized Phenol Intermediates. Effect of Oxygenated Substituents on the Yields of Spiro Dienones in Electrochemical and Iodobenzene Diacetate Oxidations

Cyclohexadienone Ketals and Quinols: Four Building Blocks Potentially Useful for Enantioselective Synthesis

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