4982-08-5Relevant academic research and scientific papers
Copper-Mediated Dichotomic Borylation of Alkyne Carbonates: Stereoselective Access to (E)-1,2-Diborylated 1,3-Dienes versus Traceless Monoborylation Affording α-Hydroxyallenes
Guo, Kun,Kleij, Arjan W.
supporting information, p. 4901 - 4906 (2021/01/21)
A mild copper-mediated protocol has been developed for borylation of alkynyl cyclic carbonates. Depending on the nature of the borylating reaction partner, either stereoselective diborylation of the propargylic surrogate takes place, providing convenient access to (E)-1,2-borylated 1,3-dienes, or traceless monoborylation occurs, which leads to α-hydroxyallenes as the principal product. The dichotomy in this borylation protocol has been scrutinized by several control experiments, illustrating that a relatively small change in the diboron(4) reagent allows for competitive alcohol-assisted protodemetalation to forge an α-hydroxyallene product under ambient conditions.
Enantioselective Access to Chiral Cyclic Sulfamidates Through Iridium-Catalyzed Asymmetric Hydrogenation
Liu, Yuanhua,Huang, Yi,Yi, Zhiyuan,Liu, Gongyi,Dong, Xiu-Qin,Zhang, Xumu
, p. 1582 - 1586 (2019/02/19)
The Iridium-catalyzed asymmetric hydrogenation of cyclic sulfamidate imines was successfully developed with N-methylated ZhaoPhos L2 as the ligand. A variety of chiral cyclic sulfamidates were obtained with excellent results (up to 99% yield, 99% ee). Furthermore, this asymmetric hydrogenation can be employed as the key reaction step to prepare the important intermediates in organic synthesis. (Figure presented.).
The Power of Triplet and Singlet Oxygen in Synthesis: 2-Oxindoles, 3-Hydroxy-2-oxindoles, and Isatins from Furans
Triantafyllakis, Myron,Sfakianaki, Kalliopi,Kalaitzakis, Dimitris,Vassilikogiannakis, Georgios
supporting information, p. 3631 - 3634 (2018/06/26)
A straightforward synthesis of substituted 2-oxindoles, 3-hydroxy-2-oxindoles, and isatins has been developed. Easily accessible furans were transformed into tetrahydropyranopyrrolones by a singlet oxygen initiated cascade reaction sequence. An acid-catal
Pd-Catalyzed Aerobic Oxidation Reactions: Strategies to Increase Catalyst Lifetimes
Ho, Wilson C.,Chung, Kevin,Ingram, Andrew J.,Waymouth, Robert M.
, p. 748 - 757 (2018/01/26)
The palladium complex [(neocuproine)Pd(μ-OAc)]2[OTf]2 (1, neocuproine = 2,9-dimethyl-1,10-phenanthroline) is an effective catalyst precursor for the selective oxidation of primary and secondary alcohols, vicinal diols, polyols, and carbohydrates. Both air and benzoquinone can be used as terminal oxidants, but aerobic oxidations are accompanied by oxidative degradation of the neocuproine ligand, thus necessitating high Pd loadings. Several strategies to improve aerobic catalyst lifetimes were devised, guided by mechanistic studies of catalyst deactivation. These studies implicate a radical autoxidation mechanism initiated by H atom abstraction from the neocuproine ligand. Ligand modifications designed to retard H atom abstractions as well as the addition of sacrificial H atom donors increase catalyst lifetimes and lead to higher turnover numbers (TON) under aerobic conditions. Additional investigations revealed that the addition of benzylic hydroperoxides or styrene leads to significant increases in TON as well. Mechanistic studies suggest that benzylic hydroperoxides function as H atom donors and that styrene is effective at intercepting Pd hydrides. These strategies enabled the selective aerobic oxidation of polyols on preparative scales using as little as 0.25 mol % of Pd, a major improvement over previous work.
Total synthesis of (+)-phenguignardic acid, a phytotoxic metabolite of Guignardia bidwellii
Stoye, Alexander,Kowalczyk, Danuta,Opatz, Till
, p. 5952 - 5960 (2013/09/23)
(+)-Phenguignardic acid, a phytotoxic metabolite of the grape black rot fungus Guignardia bidwellii was synthesized, as well as its enantiomer, in eight steps from (R)-phenyllactic acid and 3-phenylprop-2-yn-1-ol. The formation of the carboxylate at a late stage, to avoid enolization of the precursor used in the central acetalization step, proved to be crucial. The synthesis of the natural product allowed the unabiguous assignment of its hitherto unknown absolute configuration. (+)-Phenguignardic acid, a potent phytotoxic metabolite of Guignardia bidwellii, was synthesized, as well as its enantiomer, in eight steps from (R)-phenyllactic acid and 3-phenylprop-2-yn-1-ol. The absolute configuration of the natural product was determined to be S. Copyright
AuCl3/AgSbF6-catalyzed rapid epoxide to carbonyl rearrangement
Gudla, Vanajakshi,Balamurugan, Rengarajan
, p. 5243 - 5247 (2012/11/07)
An efficient epoxide to carbonyl rearrangement using catalytic AuCl 3/AgSbF6 has been presented. The reactions are fast and high yielding. β-Hydrogen migration takes place exclusively when hydrogen and methyl or substituted methyl groups are present at β-carbon of epoxide. When phenyl/acetyl/benzoyl and hydrogen are available at same carbon atom, migration of the former is preferred over the latter.
Microwave-assisted one-carbon chain extension in the preparation of terminal -hydroxy ketones
Vaismaa, Matti J. P.,Leskinen, Mikko V.,Lajunen, Marja K.
experimental part, p. 2042 - 2052 (2009/11/30)
The microwave-assisted synthesis of terminal -hydroxy ketones from acid chlorides and tris(trimethylsiloxy)ethylene in the presence of triethylamine is reported. The use of triethylamine had several advantages in the reaction: it increased the reactivity
TiCl4-promoted intramolecular cyclization of 4-methoxy-5-arylethyl-1,3-dioxolan-2-ones: an expedient method to prepare 2-tetralones
Hon, Yung-Son,Devulapally, Rammohan
experimental part, p. 2831 - 2834 (2009/09/30)
DABCO is a very effective catalyst in the formation of 4-methoxy-5-arylethyl-1,3-dioxolan-2-ones 12 from the corresponding α-carbonatoaldehyde. Intramolecular cyclization of cyclic carbonates 12 promoted by TiCl4 affords 2-tetralones 13 contain
A gold(I)-catalyzed intramolecular reaction of propargylic/homopropargylic alcohols with oxirane
Dai, Lun-Zhi,Shi, Min
supporting information; experimental part, p. 7011 - 7018 (2009/08/12)
The gold(I)-catalyzed cycloisomerization of epoxy alkynes in the presence of a nucleophile is an efficient protocol to provide ketal skeletons with high stereoselectivity. An intramolecular reaction of propargylic/homopropargylic alcohols with oxirane to produce ketal/spiroketals in moderate yields under mild conditions has been reported. Moreover, the mechanism of this kind of reaction has been discussed on the basis of a series of control and 18O tracer experiments.
Novel 3-aryl-2,5-dihydroxy-1,4-benzoquinone derivatives, their preparation method and pharmaceutical compositions containing same
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Page/Page column 4, (2008/06/13)
Compound of formula (I): wherein: R1 and R2, which may be identical or different, each represents hydrogen, acyl or alkyl, Ar represents aryl or heteroaryl, A represents a group selected from: R4 represents hydrogen or alk
