CFC- or HFC-Free Approach to α-Substituted β,γ,γ-Trifluoroallyl Alcohols by the Reaction of β-Fluoro-β-trifluoromethylated Enol Tosylate with Grignard Reagents

Funabiki, Kazumasa; Sawa, Ken‐ichi; Shibata, Katsuyoshi; Matsui, Masaki

doi:10.1055/s-2002-32607

Cited by 18 publications

(7 citation statements)

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“…Presumably, this isomerization was caused by a trace amount of bromine in the products. Alternatively, a similar isomerization was found to occur by photolysis at 254 nm for 1 h (Scheme ). − …”

Section: Synthesis Of Gem-dihalovinyl Systemsmentioning

confidence: 91%

“…Because of the high reactivity of trifluoromethylated alkenes, even those substituted in the α-position with groups such as NMe 2 (Scheme ) and OTs (Scheme ) undergo S N 2′ reactions with a variety Grignard reagents, although they need a higher temperature or longer reaction times as compared with CH 2 CH–CF 3 , CH 2 C(Ph)CF 3 , and CH 2 C(SiMe 2 Ph)CF 3 , presumably because of the steric hindrance at the reaction sites.…”

Section: Synthesis Of Gem-dihalovinyl Systemsmentioning

confidence: 99%

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Synthesis and Metal-Catalyzed Reactions of gem-Dihalovinyl Systems

2011

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Vinyl halides 24 and 25 were prepared from the tribromoromethyl carbinol 23, obtained in turn by reaction of benzo[b]thiophene-2-carboxaldehyde with the tribromomethane anion 43 generated in situ from 2,2,2-tribromoethanoic acid in DMSO (Scheme 24). 44 The intermediate 23 was treated with SOCl 2 or Et 2 NSF 3 to give the vinyl halides 24 (33% yield) or 25 (32% yield) through halogenation followed by dehydrobromination.2.1.3. Substitution Reactions. Although the most common source for gem-dibromoalkenes are carbonyl compounds, there are some examples in which alkene and alkyne derivatives have been used as starting materials. Reaction of longifolene 26 and camphene 29 with Hg(OAc) 2 /NaCl resulted in the isolation of vinylic dimercurichlorides 27 and 30, respectively (Scheme 25). These organometallics by treatment with Br 2 in pyridine afforded the related gem-dibromoalkenes 28 and 31 in very high yields. 45 Recently, 1,1-dibromo-2-arylethenes have been readily obtained in good yields (66À90%) via double ipso-bromo desilylation with N-bromosuccinimide (NBS) of 1,1-bis(trimethylsilyl)-2arylethenes, which were in turn easily obtained in high yields by Heck coupling of aryliodides with ethene-1,1-diylbis(trimethylsilane) (Scheme 26). 46 Interestingly, 1,1-bis(trimethylsilyl)-2-alkenylethenes, for example, 1,1-bis(trimethylsilyl)-4-phenylbuta-1,3-diene, under the same reaction conditions led to the selective formation of the dibrominated products containing 1,3-diene fragments.A variety of gem-dibromides were prepared from stannyl acetylenes (Scheme 27). These compounds by treatment with 1.4 equiv of Cp 2 Zr(H)Cl generated the related 1,1-heterobimetallic species of tin and zirconium, which by brominolysis with 2.5 equiv of Br 2 in CCl 4 or 3.0 equiv of N-bromosuccinimide at room temperature gave the corresponding dibromides in 53À83% yields. 47 2.1.4. Miscellaneous Reactions. Nenajdenko and co-workers reported an efficient one-pot transformation of a wide range of aldehydes and ketones into the corresponding dibromoalkenes via intermediate formation of the related hydrazones (Scheme 28). 48 Thus, these carbonyl compounds were treated with hydrazine hydrate, and when the starting materials disappeared, CBr 4 and catalytic CuCl were added to give the target products in 43À97% yields from aldehydes 48a and 43À97% yields from linear, cyclic, and caged ketones, 48a depending on the steric hindrance of the staring material. Analogously, a wide range of hydrazones of (hetero)aryl alkyl ketones (electron-rich and electron-poor) was converted into the related dibromoalkenes in 23À92% yields. 48b The proposed mechanism of the reaction starts from the oxidation of CuCl with CBr 4 to give a Cu(II) salt, which in turn oxidizes the hydrazone to the diazoalkane (Scheme 28). Decomposition of the diazoalkane generates a copperÀcarbene complex, which by interaction with CBr 4 finally leads to the dibromoalkene.

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Section: Synthesis Of Gem-dihalovinyl Systemsmentioning

confidence: 91%

Section: Synthesis Of Gem-dihalovinyl Systemsmentioning

confidence: 99%

Synthesis and Metal-Catalyzed Reactions of gem-Dihalovinyl Systems

2011

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“…Similarly, a mixture of 1-bromo-1-fluoro-2-(4-chlorophenyl)ethylene (0.24 g, 1.0 mmol, E/Z ) 88:12), NBu 3 (0.78 g, 1.14 mmol), and Cl2Pd(PPh3)2 (0.03 g, 0.04 mmol) in n-butanol (6 mL) was reacted with CO at room temperature for 134 h. When the reaction was completed, 19 F NMR analysis of the mixture showed that the Z/E ratio of the crude product was 99:1. Silica gel column chromatography (ethyl acetate/ hexanes ) 5:95, Rf ) 0.35) followed by recrystallization from hexanes gave white crystals: mp 63-65 °C; 0.20 g, yield 78% (conversion 89% based on the consumed (E)-1-bromo-1-fluoro-2-(4-chlorophenyl)ethylene), Z/E ) 100:0; 19 (29), 180 (55), 165 (9), 163 (10), 154 (16), 152 (16), 136 (7), 135 (10), 120 (80), 99 (23); HRMS calcd 256.0666 for C 13H14O2 35 ClF, obsd 256.0656. General Procedures for the Preparation of the Mixture of 4 and 7 from 1.…”

Section: Methodsmentioning

confidence: 99%

“…A variety of synthetic methods have been reported on the stereoselective synthesis of ( Z )-α-fluoro-α,β-unsaturated esters. Some examples include Cr(II)-mediated olefination of aldehydes with trifluoroacetates, Pommelet's method by Durst reaction from 3-hydroxy-2-fluoro-2-sulfinyl esters, the tandem reduction−olefination of α-fluoro-α-acylphosphonoesters, the Wittig reaction between aldehydes and trifluorinated ylides, the heteropoly acid-medicated ethanolysis of α-substituted β,γ,γ-trifluoroallyl alcohols, dehydroxylation of α-fluoro- β -hydroxy esters, thermal elimination reaction from α-fluorosulfoxide, the condensation reaction between 2-fluoro-3-oxo-succinnates and aldehydes, multistep preparation from trifluorovinyl compounds, the reaction between α-azoesters and phenylselenenyl fluoride equivalent, followed by oxidation by H 2 O 2 , Peterson olefination, one-pot reaction between aldehydes or ketones and diethyl chloromalonate in the “spray-dried” KF-sulfolane system, reductive coupling-elimination reaction between methyl dichlorofluoroacetate and carbonyl compounds in the presence of zinc(0)−copper(I) chloride, and reaction between β,β‘-dihydroxy carboxylic acid esters and vanadium(V) trichloride oxide …”

Section: Introductionmentioning

confidence: 99%

Highly Stereoselective Synthesis of (E)- and (Z)-α-Fluoro-α,β-unsaturated Esters and (E)- and (Z)-α-Fluoro-α,β-unsaturated Amides from 1-Bromo-1-fluoroalkenes via Palladium-Catalyzed Carbonylation Reactions

Burton

2005

J. Org. Chem.

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The highly stereoselective synthesis of (E)- and (Z)-alpha-fluoro-alpha,beta-unsaturated esters and (E)- and (Z)-alpha-fluoro-alpha,beta-unsaturated amides is described. 1-Bromo-1-fluoroalkenes (E/Z approximately 1:1), which are readily available starting materials, have been found to isomerize to high E/Z ratios after storage at -20 degrees C for 1 week or by photolysis at 254 nm. Since the (E)-isomers have been found to react faster than the corresponding (Z)-isomers at room temperature in Pd(0)-catalyzed reactions, the palladium-catalyzed carboalkoxylation of high E/Z 1-bromo-1-fluoroalkenes lead to a high Z/E (Z/E >/= 98:2) ratio of the alpha-fluoro-alpha,beta-unsaturated esters. When 1-bromo-1-fluoroalkenes (E/Z approximately 1:1) were reacted with HCOOH/NBu(3)/Pd(II)/DMF, the (E)-isomer was selectively reduced, and the remaining (Z)-1-bromo-1-fluoroalkenes were recovered in essentially pure isomeric form. The resulting mixture of (Z)-1-bromo-1-fluoroalkenes and the reduced products underwent similar palladium-catalyzed carboalkoxylation reactions at 70 degrees C, and the (E)-alpha-fluoro-alpha,beta-unsaturated esters were stereospecifically obtained. This methodology was also successfully applied for the stereospecific synthesis of (Z)- and (E)-alpha-fluoro-alpha,beta-unsaturated amides: the palladium-catalyzed carboamidation reaction of high E/Z and (Z)-1-bromo-1-fluoroalkenes lead to pure (Z)- and (E)-alpha-fluoro-alpha,beta-unsaturated amides, respectively.

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“…[8] In 2002, Matsui et al reported a method for synthesis of trifluoroallylic alcohols not by direct trifluorovinylation of aldehydes and ketones but by the reaction of 3,3,3,4-tetrafluoro-1-propenyl tosylate with arylmagnesium bromide. [9] In contrast to trifluoroallylic alcohols, there are only two reports on the syntheses of the corresponding silyl ethers mentioned in the literature. In 1985 and 1988, Hiyama et al showed that the reaction of benzaldehyde with triethyl-(trifluorovinyl)silane in the presence of a fluoride-ion source results in the formation of 3-triethylsiloxy-1,1,2-trifluoro-3-phenylpropene in low yield.…”

Section: Introductionmentioning

confidence: 99%

Insight into the Reactions of Trifluorovinylsilanes with Aromatic Aldehydes

et al. 2008

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The conditions for the selective addition of trialkyl(trifluorovinyl)silanes to the C=O bond of aromatic aldehydes in the presence of cesium fluoride to give the corresponding "silylated" alcohols in high yields was performed. The reactivity of the "silylated" alcohols in the presence of nucleophilic reagents and Brönsted acids was studied. On the basis of isolated compounds and of intermediates detected by NMR spectroscopic methods, several reaction pathways are proposed. Significant differences between the reaction be-

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CFC- or HFC-Free Approach to α-Substituted β,γ,γ-Trifluoroallyl Alcohols by the Reaction of β-Fluoro-β-trifluoromethylated Enol Tosylate with Grignard Reagents

Abstract: The reaction of b-fluoro-b-trifluoromethylated enol tosylate with Grignard reagents giving the corresponding b,g,g-trifluoroallyl alcohols as well as heteropoly acid-mediated ethanolysis of the allyl alcohols affording (Z)-b-substituted a-fluoro-a,b-unsaturated esters is described.

Cited by 18 publications

References 1 publication

Synthesis and Metal-Catalyzed Reactions of gem-Dihalovinyl Systems

Synthesis and Metal-Catalyzed Reactions of gem-Dihalovinyl Systems

Highly Stereoselective Synthesis of (E)- and (Z)-α-Fluoro-α,β-unsaturated Esters and (E)- and (Z)-α-Fluoro-α,β-unsaturated Amides from 1-Bromo-1-fluoroalkenes via Palladium-Catalyzed Carbonylation Reactions

Insight into the Reactions of Trifluorovinylsilanes with Aromatic Aldehydes

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