112245-13-3Relevant articles and documents
An Iridium(I) N-Heterocyclic Carbene Complex Catalyzes Asymmetric Intramolecular Allylic Amination Reactions
Ye, Ke-Yin,Cheng, Qiang,Zhuo, Chun-Xiang,Dai, Li-Xin,You, Shu-Li
, p. 8113 - 8116 (2016)
A chiral iridium(I) N-heterocyclic carbene complex was reported for the first time as the catalyst in the highly enantioselective intramolecular allylic amination reaction. The current method provides facile access to biologically important enantioenriched indolopiperazinones and piperazinones in good yields (74–91 %) and excellent enantioselectivities (92–99 % ee). Preliminary mechanistic investigations reveal that the C?H activation occurs at the position ortho to the N-aryl group of the ligand.
Iron-Catalyzed Diastereoselective Synthesis of Unnatural Chiral Amino Acid Derivatives
Zhang, Hao,Li, Haifang,Yang, Haijun,Fu, Hua
, p. 3362 - 3365 (2016)
An iron-catalyzed diastereoselective synthesis of unnatural chiral (S)-α-amino acids with γ-quaternary carbon centers has been developed. The protocol uses inexpensive iron salt as the catalyst, readily available 2-phthaloyl acrylamide and alkenes as the starting materials, and phenylsilane as the reductant, and the reactions were performed well in mixed solvent of 1,2-dichloroethane and ethylene glycol at room temperature. The method shows some advantages including simple and wide substrates, mild conditions, high diastereoselectivity, and easy workup procedures.
Highly Selective Asymmetric Acetate Aldol Reactions of an N-Acetyl Thiazolidinethione Reagent
Zhang, Yingchao,Phillips, Andrew J.,Sammakia, Tarek
, p. 23 - 25 (2004)
(Equation presented) A highly diastereoselective acetate aldol reaction that uses a tert-leucine-derived thiazolidinethione auxiliary and dichlorophenylborane has been developed. The reaction proceeds in excellent yields and with high diastereoselectivities (drs range from 9.5:1 to >100:1).
Novel 1,3,2-diazaphospholidines with pseudodipeptide substituents
Chuchelkin,Gavrilov,Firsin,Zimarev,Novikov,Maksimova,Shiryaev,Zheglov,Tafeenko,Chernyshev,Gavrilov
, p. 493 - 496 (2019)
Chiral 1,3,2-diazaphospholidine with pseudodipeptide substituents was prepared. This asymmetric inducer provided up to 84% ee in the Pd-catalyzed asymmetric allylic alkylation of (E)-1,3-diphenylallyl acetate with dimethyl malonate, and up to 53% ee in the Rh-catalyzed asymmetric hydrogenation of (Z)-methyl 2-acetamido-3-phenylacrylate.
A scalable synthesis of the (S)-4-(tert-butyl)-2-(pyridin-2-yl)-4,5- dihydrooxazole ((S)-t-BuPyOx) ligand
Shimizu, Hideki,Holder, Jeffrey C.,Stoltz, Brian M.
, p. 1637 - 1642 (2013)
An efficient method for the synthesis of the (S)-4-(tert-butyl)-2-(pyridin- 2-yl)-4,5-dihydrooxazole ((S)-t-BuPyOx) ligand has been developed. Inconsistent yields and tedious purification in known routes to (S)-t-BuPyOx suggested the need for an efficient, dependable, and scalable synthetic route. Furthermore, a route suitable for the synthesis of PyOx derivatives is desirable. Herein, we describe the development of a three-step route from inexpensive and commercially available picolinic acid. This short procedure is amenable to multi-gram scale synthesis and provides the target ligand in 64% overall yield.
Asymmetric hetero-Diels-Alder Reaction of trans-1-Methoxy-3-trimethylsilyloxy-buta-1,3-diene Catalyzed by Zinc Complexes
Buda, Szymon,Mlynarski, Jacek,Stefaniak, Matylda
, (2020)
Asymmetric hetero-Diels-Alder reactions of Danishefsky's diene and glyoxylate/pyruvate esters catalyzed by readily available zinc triflate complex with BOX ligand afforded the corresponding adduct which upon treatment with trifluoroacetic acid furnished the hetero-Diels-Alder product in 91 % enantiomeric excess and 87 % isolated yield. This reaction was applied to the concise synthesis of six-membered ulosonic acid C-glycoside.
Acetylene - Dicobaltcarbonyl complexes with chiral phosphinooxazoline ligands: Synthesis, structural characterization, and application to enantioselective intermolecular Pauson-Khand reactions
Castro, Jaume,Moyano, Albert,Pericas, Miquel A.,Riera, Antoni,Alvarez-Larena, Angel,Piniella, Joan F.
, p. 7944 - 7952 (2000)
The reaction of the phenylacetylene - dicobalthexacarbonyl complex (2) with the 4-R-2-(2-diphenylphosphinophenyl)oxazolines 1 (R = Ph) and 4 (R = CH2CH2SCH3) leads to the selective formation of the chelated complexes 3 and 5, respectively. On the other hand, the tert-butyl-substituted phosphinooxazoline 6 acts as a monodentate ligand, and its reaction with several 1-alkyne-derived complexes (2,7 - 10) affords readily separable mixtures of the diastereomer nonchelated complexes 11a,b - 15a,b. The interconversion rate between diastereomeric pairs is dependent on the steric bulk of the alkyne substituent, and neither 3 nor 5 epimerize at room temperature. The structures of both kinds of complexes have been ascertained by a combination of spectroscopical (IR, NMR), X-ray diffraction, and chiroptical methods; this has allowed the development of a practical procedure for the establishment of the absolute configuration of the chiral alkyne - dicobaltcarbonyl complexes obtained by the selective substitution of a carbon monoxide on one of the diastereotopic cobalt atoms. The intermolecular Pauson - Khand reaction of the chelated complexes 3 and 5 with norbornadiene respectively affords the (+) and (-) enantiomers of expected enone adduct 25, but in low enantiomeric excesses. Contrary to that, the tertiary amine N-oxide-promoted intermolecular Pauson - Khand reactions of nonchelated complexes 11a,b - 13a,b give the corresponding norbornadiene- or norbornene-derived adducts both in high yields (85-99%) and enantioselectivities (93-97% enantiomeric excess), in what constitutes a substantial improvement over preexisting procedures for this reaction. The possibility of achieving chiral induction in the Pauson - Khand reaction of symmetrical alkynes (via the corresponding dicobaltpentacarbonyl complexes with ligand 6) has been demonstrated for the first time. An enantioselectivity mnemonic rule and a mechanistic model that explains the observed asymmetric sense of induction have been developed, and have been found to be in agreement with the results of model semiempirical molecular orbital calculations.
Chiral auxiliary control of tacticity in free radical polymerization
Porter, Ned A.,Allen, Timothy R.,Breyer, Robert A.
, p. 7676 - 7683 (1992)
Chiral oxazolidine acrylamides undergo stereocontrolled free radical polymerization. Remarkably high degrees of tacticity have been demonstrated in the polymerization of acrylamides with these chiral auxiliaries that are derived from valine, phenylglycine, and tert-leucine. The polyacrylamides formed in these polymerizations can be converted to poly(acrylic acid), P(AA), and poly(methyl acrylate), P(MA), by hydrolysis and esterification. Tacticities as high as 92% have been measured for P(AA) and P(MA) resulting from these reactions. NMR studies of the microstructure of the polymers formed using chiral auxiliaries to control the stereochemistry of the reaction showed that the distribution of stereochemical sequences could be predicted by a statistical analysis based upon the mechanism of stereoselection. Specifically, these studies confirm that the stereocontrol is the result of facial selectivity in the addition of the monomer to the growing polymer radical. This face selectivity is thought to be the result of steric hindrance to approach of the monomer to one face of the radical caused by the chiral auxiliary. Further NMR studies were used to propose an analysis of the stereochemistry of P(MA) at the hexad level. Using HETCOR techniques, eight of the twenty hexads were conclusively identified, and a further six were narrowed to two possible choices.
Synthesis of chiral polydentate ligands and the use of their titanium complexes as pre-catalysts for the asymmetric trimethylsilylcyanation of benzaldehyde
Belokon,Chusov,Skrupskaya,Bor'Kin,Yashkina,Lyssenko,Il'In,Strelkova,Timofeeva,Peregudov,North
, p. 1981 - 1988 (2008)
A number of polydentate ligands based on enantiomerically pure binaphthol have been synthesized. The ligand complexes with titanium isopropoxide were used as catalysts for the asymmetric addition of trimethylsilyl cyanide to benzaldehyde. A fragment with axial chirality is responsible for the configuration of O-trimethylsilyl cyanohydrin product. In the case of the optimum ligand based on (R)-binaphthol and (S)-leucinol, an enantiomeric excess of 86% and quantitative yield were achieved in 4 h.
Total Synthesis of the Alleged Structure of Crenarchaeol Enables Structure Revision**
Cunha, Ana V.,Havenith, Remco W. A.,Holzheimer, Mira,Minnaard, Adriaan J.,Schouten, Stefan,Sinninghe Damsté, Jaap S.
supporting information, p. 17504 - 17513 (2021/07/06)
Crenarchaeol is a glycerol dialkyl glycerol tetraether lipid produced exclusively in Archaea of the phylum Thaumarchaeota. This membrane-spanning lipid is undoubtedly the structurally most sophisticated of all known archaeal lipids and an iconic molecule in organic geochemistry. The 66-membered macrocycle possesses a unique chemical structure featuring 22 mostly remote stereocenters, and a cyclohexane ring connected by a single bond to a cyclopentane ring. Herein we report the first total synthesis of the proposed structure of crenarchaeol. Comparison with natural crenarchaeol allowed us to propose a revised structure of crenarchaeol, wherein one of the 22 stereocenters is inverted.
