Oxidation of Furans with 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone(DDQ)

Sayama, Shinsei; Inamura, Yutaka

doi:10.3987/com-96-7456

Cited by 18 publications

(3 citation statements)

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“…26 Prior to our investigations, DDQ in wet dichloromethane had been used as a reagent for the oxidation of 2,5-diaryl-substituted 3-alkoxyfurans 14 to 1,4-diketones 15 (Scheme 7, transformation 1). 38 When 2,5-dihydrofuran 4a was reacted under the same conditions, g-keto aldehyde 5a and unconsumed starting material 4a were obtained in a ratio of approximately 1:1. This experiment showed that the presumed intermediate furan species 11 is too short-lived to be isolated.…”

Section: Methodsmentioning

confidence: 99%

3-Alkoxy-2,5-dihydrofurans by Gold-Catalyzed Allenyl Cyclizations and Their Transformation into 1,4-Dicarbonyl Compounds, Cyclopentenones, and Butenolides

Brasholz¹,

Dugovic²,

Reißig³

2010

Synthesis

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The addition of lithiated alkoxyallenes to carbonyl compounds furnishes allenyl alcohols, which undergo a highly efficient and chemoselective 5-endo-trig cyclization to 3-alkoxy-2,5-dihydrofurans catalyzed by gold(I) chloride. The dihydrofurans produced can be either oxidized to b-alkoxy butenolides by a manganese(III) acetate catalyzed radical oxidation with tert-butyl hydroperoxide, or transformed into a,b-unsaturated g-keto aldehydes by an oxidative ring cleavage using DDQ in the presence of water. Treatment of the g-keto aldehydes with sodium methoxide in methanol promotes a diastereoselective intramolecular aldol addition furnishing alkoxy-substituted cyclopentenone derivatives in good yield.

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Section: Methodsmentioning

confidence: 99%

3-Alkoxy-2,5-dihydrofurans by Gold-Catalyzed Allenyl Cyclizations and Their Transformation into 1,4-Dicarbonyl Compounds, Cyclopentenones, and Butenolides

Brasholz¹,

Dugovic²,

Reißig³

2010

Synthesis

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“…As shown in Scheme , when treated with the same oxidative and acidic reagents, 4-aryl-2-α-acetoxyalkyl furan 45 was transformed into product 50 having a cis -enedione skeleton, in contrast to the trans -enedione skeleton formed from the (otherwise identical) 4-hydrido derivative 34 (see 34 → 37 , Scheme ) . The selective formation of products having a cis -enedione skeleton proved to be general for a series of 4-aryl-2-α-acetoxyalkyl furans similar to 45 that were synthesized and tested.…”

Section: Generating Skeletal Diversity Combinatoriallymentioning

confidence: 95%

A Synthesis Strategy Yielding Skeletally Diverse Small Molecules Combinatorially

2004

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The efficient synthesis of small molecules having many molecular skeletons is an unsolved problem in diversity-oriented synthesis (DOS). We describe the development and application of a synthesis strategy that uses common reaction conditions to transform a collection of similar substrates into a collection of products having distinct molecular skeletons. The substrates have different appendages that pre-encode skeletal information, called sigma-elements. This approach is analogous to the natural process of protein folding in which different primary sequences of amino acids are transformed into macromolecules having distinct three-dimensional structures under common folding conditions. Like sigma-elements, the amino acid sequences pre-encode structural information. An advantage of using folding processes to generate skeletal diversity in DOS is that skeletal information can be pre-encoded into substrates in a combinatorial fashion, similar to the way protein structural information is pre-encoded combinatorially in polypeptide sequences, thus making it possible to generate skeletal diversity in an efficient manner. This efficiency was realized in the context of a fully encoded, split-pool synthesis of approximately 1260 compounds potentially representing all possible combinations of building block, stereochemical, and skeletal diversity elements.

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“…Although the projected DIBAL reaction can be performed at this stage of the synthesis, this step was delayed until after the deprotection of the methoxybenzyl group because of the known sensitivity of furan to oxidative methoxybenzyl-deprotection conditions [26]. Consequently, the methoxybenzyl group in 24 and 25 was deprotected with DDQ in wet CH 2 Cl 2 [27] to furnish a mixture of alcohols 26 and 27 in a 3 : 2 ratio.…”

mentioning

confidence: 99%

Chromium‐Mediated Dearomatization: Application to the Synthesis of Racemic 15‐Acetoxytubipofuran and Asymmetric Synthesis of Both Enantiomers

Kündig

Laxmisha

Cannas

et al. 2005

Helvetica Chimica Acta

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An efficient dearomatization process of [Cr(arene)(CO) 3 ] complexes initiated by a nucleophilic acetaldehyde equivalent is detailed. It generates in a one-pot reaction three CÀC bonds and two stereogenic centers. This process allowed a rapid assembly of a cis-decalin ring system incorporating a homoannular diene unit in just two steps starting from aromatic precursors (Scheme 2). The method was applied to the total synthesis of the eudesmane-type marine furanosesquiterpene (AE)-15-acetoxytubipofuran (2). Two routes were successfully used to synthesize the g-lactone precursor of the furan ring. The key step in the first approach was a Pd-catalyzed allylic substitution (Scheme 3), while in the second approach, an Eschenmoser ± Claisen rearrangement was highly successful (Scheme 4). The Pd-catalyzed allylic substitution could be directed to give either the (normal) product with overall retention as major diastereoisomer or the unusual product with inversion of configuration (see Table). For the synthesis of the (À)-enantiomer (R,R)-2 of 15-acetoxytubipofuran, an enantioselective dearomatization in the presence of a chiral diether ligand was implemented (Scheme 7), while the ()-enantiomer (S,S)-2 was obtained via a diastereoselective dearomatization of an arene-bound chiral imine auxiliary (Scheme 8). Chiroptical data suggest that a revision of the previously assigned absolute configuration of the natural product is required.Introduction. ± Tricarbonylchromium-mediated dearomatization provides an efficient access to polysubstituted cyclohexadienes [1]. Up to three C-substituents can be added across an arene double bond in a one-pot procedure in a regio-and stereoselective manner by a sequential nucleophilic/electrophilic addition or by a nucleophilic addition followed by an acylation/alkylation sequence [2]. This dearomatization method has seen considerable development, with recent efforts mainly directed towards asymmetric variants of this reaction to give enantiomerically enriched products. Four different asymmetric methods have been developed: asymmetric induction with complexes of arenes bearing a chiral auxiliary as substituent [3], use of arene complexes possessing planar chirality [4], use of prochiral complexes with chiral nucleophiles [5], and use of complexes containing a chiral ligand at the chromium atom [6]. Benchmark enantio-and diastereoselectivities have been obtained in dearomatizations with these methods. In all but the last method, asymmetric induction takes place during the nucleophilic addition step. The third method offers an enantioselective variant in that chirality can be centered on an external ligand rather than on the nucleophile itself, and first results of the use of substoichiometric quantities of chiral information have been realized [7].In all of the dearomatization processes mentioned above, the products possess a homoannular cyclohexadiene moiety. This subunit embedded in a cis-decalin ring

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Oxidation of Furans with 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone(DDQ)

Cited by 18 publications

References 0 publications

3-Alkoxy-2,5-dihydrofurans by Gold-Catalyzed Allenyl Cyclizations and Their Transformation into 1,4-Dicarbonyl Compounds, Cyclopentenones, and Butenolides

3-Alkoxy-2,5-dihydrofurans by Gold-Catalyzed Allenyl Cyclizations and Their Transformation into 1,4-Dicarbonyl Compounds, Cyclopentenones, and Butenolides

A Synthesis Strategy Yielding Skeletally Diverse Small Molecules Combinatorially

Chromium‐Mediated Dearomatization: Application to the Synthesis of Racemic 15‐Acetoxytubipofuran and Asymmetric Synthesis of Both Enantiomers

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