55514-48-2Relevant academic research and scientific papers
Asymmetric synthesis of α,β-substituted γ-amino acids via conjugate addition
Sabala, Rocío,Assad, Salomon,Mendoza, ángel,Jiménez, Jacqueline,Sansinenea, Estibaliz,Ortiz, Aurelio
, p. 1741 - 1744 (2019)
The first conjugate addition reaction of organocuprates to N-enoyl oxazolidinone where a N-protected γ-nitrogen atom and an α-methyl group are present into α, β-unsaturated system is described. This reaction gave anti-products in moderate yields and high diastereomeric ratios. The anti-products have two contiguous stereogenic centers, one formed by the conjugate addition reaction and the other by a diastereoselective protonation reaction. The removal of chiral oxazolidinone moiety and N-deprotection of amino group furnished chiral α, β-disubstituted γ-amino acids.
Catalytic Asymmetric Vinylogous Mukaiyama-Aldol (CAVM) reactions: The enolate activation
Bluet,Campagne
, p. 4293 - 4298 (2001)
The Catalytic Asymmetric Vinylogous Mukaiyama (CAVM) reactions of various aldehydes with dienolate 1 using different enolate activations (CuF·(S)-TolBinap, t-BuOCu·(S)-Tol-Binap, and various chiral nonracemic ammonium fluorides derived from cinchona alkal
Olefination via Cu-Mediated Dehydroacylation of Unstrained Ketones
Dong, Guangbin,Xu, Yan,Zhou, Xukai
supporting information, p. 20042 - 20048 (2021/12/03)
The dehydroacylation of ketones to olefins is realized under mild conditions, which exhibits a unique reaction pathway involving aromatization-driven C-C cleavage to remove the acyl moiety, followed by Cu-mediated oxidative elimination to form an alkene between the α and β carbons. The newly adopted N′-methylpicolinohydrazonamide (MPHA) reagent is key to enable efficient cleavage of ketone C-C bonds at room temperature. Diverse alkyl- and aryl-substituted olefins, dienes, and special alkenes are generated with broad functional group tolerance. Strategic applications of this method are also demonstrated.
Highly Enantioselective Iridium-Catalyzed Hydrogenation of Conjugated Trisubstituted Enones
Peters, Bram B. C.,Jongcharoenkamol, Jira,Krajangsri, Suppachai,Andersson, Pher G.
supporting information, p. 242 - 246 (2021/01/13)
Asymmetric hydrogenation of conjugated enones is one of the most efficient and straightforward methods to prepare optically active ketones. In this study, chiral bidentate Ir-N,P complexes were utilized to access these scaffolds for ketones bearing the stereogenic center at both the α- and β-positions. Excellent enantiomeric excesses, of up to 99%, were obtained, accompanied with good to high isolated yields. Challenging dialkyl substituted substrates, which are difficult to hydrogenate with satisfactory chiral induction, were hydrogenated in a highly enantioselective fashion.
Asymmetric Aza-Wacker-Type Cyclization of N-Ts Hydrazine-Tethered Tetrasubstituted Olefins: Synthesis of Pyrazolines Bearing One Quaternary or Two Vicinal Stereocenters
Kou, Xuezhen,Shao, Qihang,Ye, Chenghao,Yang, Guoqiang,Zhang, Wanbin
, p. 7587 - 7597 (2018/06/04)
We have developed an asymmetric aza-Wacker-type cyclization of N-Ts hydrazine-tethered tetrasubstituted olefins, affording optically active pyrazolines bearing chiral tetrasubstituted carbon stereocenters. This reaction is tolerant to a broad range of substrates under mild reaction conditions, giving the desired chiral products with high enantioselectivities. Generation of two vicinal stereocenters on the C=C double bonds was also achieved with high selectivities, a process which has been rarely studied for Wacker-type reactions. A mechanistic study revealed that this aza-Wacker-type cyclization undergoes a syn-aminopalladation process. It was also found that for substrates bearing two linear alkyl substituents on the outer carbon atom of the olefin, both of which are larger than a methyl group, the alkyl substituent that is cis to the intranucleophilic group participates more readily in β-hydride elimination. When one of the two alkyl substituents on the outer carbon atom of the olefin is a methyl group, β-hydride elimination proceeds selectively at the methylene side, thus both diastereomers can be prepared via switching the configuration of the olefin. Furthermore, the product can be converted to a pharmaceutical compound in high yields over three steps.
2-alkyl substituted crotonic acid and ester synthesis method thereof
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Paragraph 0057; 0058, (2017/02/17)
The invention provides a 2-alkyl substituted crotonic acid and an ester synthesis method thereof.The ester synthesis methodincludes the following steps that 2-alkyl butyric acid, a first catalyst and halogen are used as raw materials to synthesize 2-halogeneated-alkyln-butyric acid; the 2-halogeneated-alkyln-butyric acid, a solvent and inorganic base are used as raw materials to synthesize 2-alkyl crotonic acid; the 2-alkyl crotonic acid, a second catalyst and alcohol are used as raw materials to synthesize 2-alkyl crotonic acid ester. The 2-alkyl substituted crotonic acid and the ester synthesis method have the advantages that the solvents used in all reaction steps are recyclable, a water phase is recycled after finished product filtering, no wastewater is discharged, and a byproduct haloid acid (particularly referring to hydrobromic acid and hydrochloric acid) is obtained after halogen hydridetail gas is absorbed.
Highly enantioselective iridium-catalyzed hydrogenation of α,β-unsaturated esters
Li, Jia-Qi,Quan, Xu,Andersson, Pher G.
supporting information, p. 10609 - 10616 (2012/11/07)
α,β-Unsaturated esters have been employed as substrates in iridium-catalyzed asymmetric hydrogenation. Full conversions and good to excellent enantioselectivities (up to 99 % ee) were obtained for a broad range of substrates with both aromatic- and aliphatic substituents on the prochiral carbon. The hydrogenated products are highly useful as building blocks in the synthesis of a variety of natural products and pharmaceuticals. Asymmetric hydrogenation: A variety of α,β-unsaturated esters were hydrogenated with high enantioselectivities (see scheme). The hydrogenated products have been used in synthetic transformations as well as in formal total syntheses. Copyright
Rh-catalyzed asymmetric hydroformylation of functionalized 1,1-disubstituted olefins
Wang, Xiao,Buchwald, Stephen L.
supporting information; experimental part, p. 19080 - 19083 (2012/01/05)
The first method for the highly enantioselective rhodium-catalyzed hydroformylation of 1,1-disubstituted olefins has been developed. By employing either of the P-chirogenic phosphine ligands BenzP* and QuinoxP*, linear aldehydes with β-chirality can be prepared in a highly enantioselective fashion with good chemo- and regioselectivities.
Efficient preparation of α,α-dialkyl-α-(phenylselanyl) acetates and α,β-unsaturated esters from the corresponding α,α-dialkyl-α-cyanoacetates by a lithium naphthalenide induced reductive selenenylation process
Ko, Yen-Chun,Zhu, Jia-Liang
, p. 3659 - 3665 (2008/09/19)
An array of α,α-dialkyl-α-(phenylselanyl)acetates has been synthesized very efficiently from readily available α,α- dialkyl-α-cyanoacetates, by use of lithium naphthalenide induced reductive α-selenenylation as a key operation. Moreover, the selanyl esters thus generated in situ could be converted further, in a one-pot treatment with hydrogen peroxide and acetic acid, into the corresponding α,β- unsaturated esters in moderate to high yields. The C=C bond formation was highly regio- and/or diastereoselective in some cases. Georg Thieme Verlag Stuttgart.
Synthesis and resolution of 2-methyl analogues of GABA
Duke, Rujee K.,Chebib, Mary,Hibbs, David E.,Mewett, Kenneth N.,Johnston, Graham A.R.
, p. 1745 - 1751 (2007/10/03)
E-4-Amino-2-methylbut-2-enoic acid, (±)-4-amino-2-methylbutanoic acid, (+)-(S)- and (-)-(R)-4-amino-2-methylbutanoic acid, which are analogues of the inhibitory neurotransmitter GABA (γ-aminobutyric acid, 4-aminobutanoic acid), were synthesised from ethyl 2-methyl-4-phthalimidobut-2- enoate, ethyl 2-methyl-4-phthalimidobutanoate, (+)-[(2R-(3,3-dimethylbutyro-1,4- lactonyl)]-(2S)-methyl-4-phthalimidobutanoate and (-)-[(2R-(3,3-dimethylbutyro- 1,4-lactonyl)]-(2R)-methyl-4-phthalimidobutanoate, respectively. The assignment of the absolute configuration of (+)-(S)- and (-)-(R)-4-amino-2-methylbutanoic acid was based on the X-ray crystallographic structure of the (+)-(R,S)-diastereoisomer, and direct comparison of specific rotations with the published data for (-)-(R)-4-amino-2-methylbutanoic acid.
