Aryne reaction with trifluoromethyl ketones in three modes: C–C bond cleavage, [2+2] cycloaddition and O-arylation

Yoshida, Hiroto; Ito, Yu; Yoshikawa, Yunito; Ohshita, Joji; Takaki, Ken

doi:10.1039/c1cc12820e

Cited by 45 publications

(16 citation statements)

References 22 publications

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“…Thus, treatment of arynes with 9-fluorenyl ketones leads to facile insertion into the C(methine)-C(carbonyl) bond to give the acylfluorenylation products, 169 where formation of the key carbanionic species is facilitated by its aromatic stabilization (Scheme 49), and furthermore arynes are also inserted into various benzyl trifluoromethyl ketones (Scheme 50). 170 The reaction with trifluoromethyl mesitylmethyl ketone gives (Z)-O-arylation product 51 solely, which is attributable to stereoselective formation of enolate 50, and exclusive production of benzocyclobutenol 52 by use of trifluoromethyl phenethyl ketone suggests concerted nature of [2 þ 2] cycloaddition (see Section 4.09.3.2.5).…”

Section: 2 Addition Of R-bondsmentioning

confidence: 97%

4.09 Nucleophilic Coupling with Arynes

Yoshida

2014

Comprehensive Organic Synthesis II

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Section: 2 Addition Of R-bondsmentioning

confidence: 97%

4.09 Nucleophilic Coupling with Arynes

Yoshida

2014

Comprehensive Organic Synthesis II

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“…Yoshida reported an analogous acyl-alkylation method to ours, but using trifluoromethyl ketones (2, Scheme 1). 6 The trifluoromethyl group is required because it enhances the acidity of the a-keto C-H bonds. The authors note that the presence of bulky R groups on the aryl system of 2 results in competitive O-addition of the enolate intermediate.…”

Section: Tmsmentioning

confidence: 99%

Discussion Addendum for: The Direct Acyl-Alkylation of Arynes. Preparation of Methyl 2-(2-acetylphenyl)acetate

Wright¹

2019

Org. Synth.

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“…(2-Cyclopropyl-4-hydroxyphenyl)(phenyl)methanone (17) Aq K 2 CO 3 (5%, 5 mL) was added in one portion to a solution of 16 (60 mg, 0.14 mmol) in CHCl 3 (5 mL). The mixture was stirred for 16…”

Section: Special Topic Syn Thesismentioning

confidence: 99%

“…Cyclobutenes could also be obtained by addition of arynes to cyclic enol ethers 15 or the enolates of trifluoromethyl ketones. 16 A characteristic property of cyclobutenes is their tendency to undergo a thermally induced electrocyclic ringopening reaction, resulting in the formation of isomeric 1,3-butadienes. 17 For monocyclic cyclobutenes, the conrotatory stereochemical course of the concerted process can usually be achieved without steric constraints and the acti-vation energy is rather low.…”

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confidence: 99%

Cycloaddition Reactions of Propyne Iminium Salts and Enol Ethers

2015

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Acetylenic iminium salts (propyne iminium salts) react with cyclic enol ethers in a thermal [2+2] cycloaddition reaction to afford condensed cyclobutene iminium salts. With acyclic enol ethers, a cycloaddition/electrocyclic ring-opening sequence occurs to give (1-alkoxybuta-1,3-dien-2-yl)methane iminium salts as mixtures of diastereoisomers. An analogous scenario is observed with 5-phenyl-2-vinylfuran as the nucleophilic olefinic component. With 1-methoxy-3-trimethylsilyloxy-1,3-butadiene, propyne iminium salts undergo a [4+2] cycloaddition. For all reactions, traces of acid must be quenched with solid K 2 CO 3 or CaO to avoid immediate polymerization of the enol ether.The [2+2] cycloaddition strategy appears to provide an obvious route to carbocyclic four-membered rings from two substrates containing carbon-carbon π bonds, and, indeed, this approach has been used to prepare a variety of substituted cyclobutanes 1 and cyclobutenes. 2 However, as the thermally induced concerted [ π 2 s + π 2 s ] cycloaddition is not allowed based on orbital symmetry conservation, 3 and the allowed [ π 2 s + π 2 a ] geometry is usually prohibited for steric reasons, the scope of this reaction type is limited to certain types of alkenes and alkynes; in particular, those that stabilize radical or zwitterionic reaction intermediates. 1a Thus, it is well known that electrophilic and nucleophilic alkenes combine to form cyclobutanes with rather moderate activation energies. Mechanistic investigations and product analyses by Huisgen and co-workers on the reaction of enol ethers with the extremely electron-poor olefins tetracyanoethene 4 and 1,2-bis(trifluoromethyl)ethene-1,2-dicarbonitrile 5 have provided compelling evidence for the two-step reaction course via 1,4-zwitterions. The synthetically useful synthesis of donor/acceptor-substituted cyclobutanes from silyl enol ethers (or dihydrofuran) and α,β-unsaturated esters was performed effectively under catalysis by Lewis acids or bis(triflyl)amide. 6,7

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Aryne reaction with trifluoromethyl ketones in three modes: C–C bond cleavage, [2+2] cycloaddition and O-arylation

Abstract: Trifluoromethyl ketones were found to be coupled with arynes in three modes depending upon their substitution patterns, namely C-C bond cleavage, [2+2] cycloaddition and O-arylation.

Cited by 45 publications

References 22 publications

4.09 Nucleophilic Coupling with Arynes

4.09 Nucleophilic Coupling with Arynes

Discussion Addendum for: The Direct Acyl-Alkylation of Arynes. Preparation of Methyl 2-(2-acetylphenyl)acetate

Cycloaddition Reactions of Propyne Iminium Salts and Enol Ethers

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