Synthesis of α-Trifluoromethylated Carboxylic Acid Esters

Kitazume, Tomoya; Ohnogi, Takeshi

doi:10.1055/s-1988-27653

Cited by 34 publications

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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%

“…Trifluoromethyl and bromodifluoromethyl alkene derivatives 62 with either electron-withdrawing or electron-donating substituents at the α-carbon smoothly underwent nucleophilic addition–elimination (via dehalogenation) reactions on reacting with carbon and heteroatom nucleophiles to give functionalized 1,1-difluoroalkenes 63 (Scheme ). Thus, S N 2′ reaction of organolithiums, Grignard reagents, − N-lithiated amines, lithium aluminum hydride, ester enolates, or silyl lithium reagents with trifluoromethyl-substituted alkenes afforded the corresponding gem -difluoroalkenes (Scheme ).…”

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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“…273 The 2-trifluoromethylpropenoate (176) reacts with RMCu to give (177) which can be converted into (178) by treatment with Bu,NF-TsOH followed by water. 274 The alane (179) reduces275 the alkynone (1 80) to the corresponding (S)-alcohol of 92 % e.e. Various 1,3- The alcohols (1 84) react280 in FS0,H-SO, to give the bicyclic ethers (185) which can be separated by preparative GC.…”

Section: Menthanesmentioning

confidence: 99%

“…Oxidation of camphene (228) using trioxoosmium(8) tbutylimide yields the aminoalcohol (270)331 and autoxidation of camphene in the presence of catalytic cobalt naphthenate gives332 the epoxide (271) together with some camphenilone (272). Treatment of camphene (228) with alcohols in the presence of a zeolite affords isobornyl alkyl Camphene (228) has been into the allene (273); camphor (229) has been converted via (274) into the analogous allene (275).…”

Section: Camphanes and Lsocamphanesmentioning

confidence: 99%

Monoterpenoids

Grayson¹

1992

Nat. Prod. Rep.

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Introduction 2 2,6-Dimethyloctanes 3 Irregular Monoterpenoids 4 Menthanes 5 Cineol Derivatives 6 Camphanes and Isocamphanes 7 Pinanes 8 Caranes 9 Fenchanes 10 Thujanes 11 Ionone Derivatives 12 Iridanes 13 Cannabinoids I4 References NATURAL PRODUCT REPORTS, 1992-D. H. GRAYSON 533 Table 1 Plant species Abies spp. Abies alba Achillea abrotanoides Ambrosia trcfida A r t em isia scoparia Bidens pilosa Buddleia sal vifolia Cestrum nocturnum Chaerophyllum bulbosum spp. Citrus aurantium var. Citrus limoniu var. Osbeck Comptonia peregrina Cymbopogon distans f. Drucocephalum moldavica Elettaria cardamomum Maton. Elsholtzia blanda E. pilosa E. polysracha E. stauntonii Eucalyptus Pscerta Feronia limonia Fil ipendula ulniar ia Fissistigma shangtzeense Gutierrezia surothrae Hyp t is pee tinu ta H . suaveolens Poit. Hyssopus oficinalis Illicium simonsii Juniperus recurvata var. Levisticum ojicinale Lomatium grayi Melaleuca alternjfolia Melissa oficinalis Mentha arvensis Mercurialis Ieiocarpa Micromeria teneriflae Benth. Momordica charantia Monodoru myristica Murraya spp. M . k wangsiensis Ocimum basilicum 0 lear ia p h logo pap pa Origanum mujorana 0. onites Picea abies Karst. Pinus cretacea Kollenicz. Piper nigrum Ribes nigrum Ribes nigrum Rosa cymosa Salvia lavandulaefolia sspp.

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Organocopper Reagents: Substitution, Conjugate Addition, Carbo/Metallocupration, and Other Reactions

1992

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Well over a decade ago, two reviews were contributed to the Organic Reactions series covering substitution and conjugate addition reactions in organocopper chemistry. Their appearance, which highlighted most of the early work in this field, served not only as a source of invaluable references to original literature reports, but also stimulated a vast number of subsequent studies on the properties and uses of organocopper complexes. The work cited in this chapter, which dates from ca. 1975, concerns in large measure uses of organocopper complexes originating from either catalytic or stoichiometric quantities of a copper(I) halide together with a Grignard (RMgX) or organolithium (RLi) reagent. These combinations form either neutral organocopper reagents RCu ( 1 ) or copper(I) monoanionic salts R 2 CuM (M = Li or MgX), commonly referred to as “lower‐order” species. The latter ate complexes with lithium as gegenion ( 2 ) are also known as “Gilman reagents” in recognition of their origins. Copper(I) cyanide is also an excellent precursor, affording homogeneous mixtures of lower order cyanocuprates RCu(CN)Li, ( 3 ), upon treatment with an equivalent of an organolithium. The strength of the CuCN linkage presumably accounts for direct cuprate formation with 1 equivalent of the organolithium, rather than the metathesis that occurs with copper(I) chloride, bromide, or iodide. While use of reagents ( 1 ), ( 2 ) and ( 3 ) alone can be aptly classified as broad‐based and intense, their importance has further encouraged extensive development of variations on these themes (i.e., their composition and reactivity profiles). Reagents ( 1–3 ) have been found to be unexpectedly compatible with certain electrophilic additives at low temperatures, which substantially alter their reactivity. Rather than forming ( 2 ) from 2 equivalents of the same RLi, different organolithiums can be utilized to give R T R R CuLi, ( 4 ), conserving potentially valuable RLi. This scenario raises the question of controlling the selectivity of transfer of the desired ligand R T rather than the anticipated residual (or “dummy”) group R R from copper to electrophilic carbon. Fortunately, many solutions to this problem now exist. Admixture of 2RLi (or R T Li + R R Li) with copper(I) cyanide proceeds beyond the stage of ( 3 ) to ultimately arrive at copper(I) dianionic complexes 5 , the so‐called “higher‐order” cyanocuprates. Undoubtedly it is the cyano ligand, with its π‐acidic nature, which enables copper to accept a third negatively charged ligand. Although reagents ( 5 ) do not yet share in all of the benefits offered by time in comparison with their lower‐order counterparts, they nicely complement prior art. Moreover, as with species ( 1–4 ), they continue to evolve, providing the synthetic community with alternatives for highly selective and efficient means of making key carbon–carbon bonds.

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Synthesis of α-Trifluoromethylated Carboxylic Acid Esters

Cited by 34 publications

References 0 publications

Synthesis and Metal-Catalyzed Reactions of gem-Dihalovinyl Systems

Synthesis and Metal-Catalyzed Reactions of gem-Dihalovinyl Systems

Monoterpenoids

Organocopper Reagents: Substitution, Conjugate Addition, Carbo/Metallocupration, and Other Reactions

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