- Photochemical Deracemization at sp3-Hybridized Carbon Centers via a Reversible Hydrogen Atom Transfer
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A photochemical deracemization of 5-substituted 3-phenylimidazolidine-2,4-diones (hydantoins) is reported (27 examples, 69%-quant., 80–99% ee). The reaction is catalyzed by a chiral diarylketone which displays a two-point hydrogen bonding site. Mechanistic evidence (DFT calculations, radical clock experiments, H/D labeling) suggests the reaction to occur by selective hydrogen atom transfer (HAT). Upon hydrogen binding, one substrate enantiomer displays the hydrogen atom at the stereogenic center to the photoexcited catalyst allowing for a HAT from the substrate and eventually for its conversion into the product enantiomer. The product enantiomer is not processed by the catalyst and is thus enriched in the photostationary state.
- Bach, Thorsten,Breitenlechner, Stefan,Gro?kopf, Johannes,Plaza, Manuel,Seitz, Antonia,Storch, Golo
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supporting information
p. 21241 - 21245
(2021/12/27)
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- Synthesizing Molecules with Linear Tricyclic 5/5/5 and 6/5/5 Skeletons via [5 + 2 + 1]/Ene Strategy
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Report here is the development of a [5 + 2 + 1]/ene strategy for the synthesis of molecules with linear tricyclic 5/5/5 and 6/5/5 skeletons widely found in natural products. The first step of this strategy is applying a Rh-catalyzed [5 + 2 + 1] reaction o
- Liu, Jing,Zhou, Yi,Zhu, Jiaqi,Yu, Zhi-Xiang
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supporting information
p. 7566 - 7570
(2021/10/02)
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- Nitrile Synthesis by Aerobic Oxidation of Primary Amines and in situ Generated Imines from Aldehydes and Ammonium Salt with Grubbs Catalyst
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Herein, a Grubbs-catalyzed route for the synthesis of nitriles via the aerobic oxidation of primary amines is reported. This reaction accommodates a variety of substrates, including simple primary amines, sterically hindered β,β-disubstituted amines, allylamine, benzylamines, and α-amino esters. Reaction compatibility with various functionalities is also noted, particularly with alkenes, alkynes, halogens, esters, silyl ethers, and free hydroxyl groups. The nitriles were also synthesized via the oxidation of imines generated from aldehydes and NH4OAc in situ. (Figure presented.).
- Utsumi, Tatsuki,Noda, Kenta,Kawauchi, Daichi,Ueda, Hirofumi,Tokuyama, Hidetoshi
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supporting information
p. 3583 - 3588
(2020/08/05)
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- Bromomethyl Silicate: A Robust Methylene Transfer Reagent for Radical-Polar Crossover Cyclopropanation of Alkenes
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A general protocol for visible-light-induced cyclopropanation of alkenes was developed with bromomethyl silicate as a methylene transfer reagent, offering a robust tool for accessing highly valuable cyclopropanes. In addition to α-aryl or methyl-substituted Michael acceptors and styrene derivatives, the unactivated 1,1-dialkyl ethylenes were also shown to be viable substrates. Apart from realizing the cyclopropanation of terminal alkenes, the methyl transfer reaction has been further demonstrated to be amenable to the internal olefins. The photocatalytic cyclopropanation of 1,3-bis(1-arylethenyl)benzenes was also achieved, giving polycyclopropane derivatives in excellent yields. With late-stage cyclopropanation as the key strategy, the synthetic utility of this transformation was also demonstrated by the total synthesis of LG100268.
- Luo, Wenping,Fang, Yewen,Zhang, Li,Xu, Tianhang,Liu, Yongjun,Li, Yan,Jin, Xiaoping,Bao, Jiakan,Wu, Xiaodong,Zhang, Zongyong
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supporting information
p. 1778 - 1781
(2020/03/11)
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- Synthesis of 1-hydrocarbon substituted cyclopropyl silyl ketones
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The synthesis of cyclopropyl silyl ketones possessing a hydrocarbon group at 1-position of three-membered ring was investigated. The reaction of sulfoxonium ylide with α,β-unsaturated acylsilanes derived from α,β-unsaturated aldehydes did not afford the desired acylsilane derivatives. Instead, the corresponding silyl enol ethers were yielded exclusively. On the other hand, the Corey-Chaykovsky cyclopropanation of α-substituted α,β-unsaturated aldehydes proceeded well to give 1-substituted cyclopropyl aldehydes. The silyl substitution of formyl proton in the obtained aldehydes via umpolung of carbonyl group afforded the target acylsilanes.
- Honda, Mitsunori,Sasaki, Sho,Nishimoto, Tsuyoshi,Koshiro, Hiromoto,Kunimoto, Ko-Ki,Segi, Masahito
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p. 3777 - 3781
(2018/09/21)
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- Olefin-Migrative Cleavage of Cyclopropane Rings through the Nickel-Catalyzed Hydrocyanation of Allenes and Alkenes
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A nickel-catalyzed hydrocyanation triggered by hydronickelation of the carbon-carbon double bonds of allenes followed by cyclopropane cleavage is described. The observed regio- and stereochemistries in the products are strongly influenced by the initial hydronickelation step, and allenyl- and methylenecyclopropanes reacted smoothly to promote the cleavage of cyclopropane. In contrast, this cleavage was not observed with vinylidenecyclopropanes, because the initial hydronickelation does not give a suitable intermediate for cleavage of the cyclopropanes. (Figure presented.).
- Hori, Hiroto,Arai, Shigeru,Nishida, Atsushi
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p. 1170 - 1176
(2017/04/13)
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- Design of Potent and Druglike Nonphenolic Inhibitors for Catechol O-Methyltransferase Derived from a Fragment Screening Approach Targeting the S-Adenosyl- l -methionine Pocket
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A fragment screening approach designed to target specifically the S-adenosyl-l-methionine pocket of catechol O-methyl transferase allowed the identification of structurally related fragments of high ligand efficiency and with activity on the described orthogonal assays. By use of a reliable enzymatic assay together with X-ray crystallography as guidance, a series of fragment modifications revealed an SAR and, after several expansions, potent lead compounds could be obtained. For the first time nonphenolic and small low nanomolar potent, SAM competitive COMT inhibitors are reported. These compounds represent a novel series of potent COMT inhibitors that might be further optimized to new drugs useful for the treatment of Parkinson's disease, as adjuncts in levodopa based therapy, or for the treatment of schizophrenia.
- Lerner, Christian,Jakob-Roetne, Roland,Buettelmann, Bernd,Ehler, Andreas,Rudolph, Markus,Sarmiento, Rosa María Rodríguez
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p. 10163 - 10175
(2016/12/07)
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- Biarylphosphonite gold(I) complexes as superior catalysts for oxidative cyclization of propynyl arenes into indan-2-ones
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Striking gold: A series of variously functionalized propynyl arenes was smoothly converted into indan-2-ones by a new gold(I)-catalyzed oxidative cyclization process. [LAu]NTf2 (Tf=trifluoromethanesulfonyl) is a superior catalyst both in terms of yield and kinetics for the present transformation. Copyright
- Henrion, Guilhem,Chavas, Thomas E. J.,Le Goff, Xavier,Gagosz, Fabien
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supporting information
p. 6277 - 6282
(2013/07/11)
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- INHIBITORS OF HEPATITIS C VIRUS POLYMERASE
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The present invention provides, among other things, compounds represented by the general Formula (I) and pharmaceutically acceptable salts thereof, wherein X, Y, R1A, R1B, R2, and R3 are as defined in classes and subclasses herein and compositions (e.g., pharmaceutical compositions) comprising such compounds, which compounds are useful as inhibitors of hepatitis C virus polymerase, and thus are useful, for example, as medicaments for the treatment of HCV infection.
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- A convenient ring formation of 3-aryl-2,2-dialkyl-2,3-dihydrobenzofurans from phenols and 2-aryl-2,2-dialkylacetaldehydes
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A new and simple route for the preparation of 3-aryl-2,2-dialkyl-2,3- dihydrobenzofurans from phenols is described. In the presence of an acid catalyst phenols react with 2-aryl-2,2-dialkylacetaldehydes, prepared in good yield from 2-arylacetonitriles in 2 steps, to give 3-aryl-2,2-dialkyl-2,3- dihydrobenzofurans. Electron-donating substituents were required on the phenols in order to give 3-aryl-2,2-dialkyl-2,3-dihydrobenzofurans in good yield.
- Yamashita, Makoto,Ono, Yujirou,Tawada, Hiroyuki
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p. 2843 - 2849
(2007/10/03)
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- Deamination Reactions, 42. Addition of Diazocyclopropanes to Carbonyl Compounds
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Diazocyclopropanes (6, 38, 57) were generated in equilibrium with cyclopropanediazonium ions by base-induced cleavage of the analogous nitrosoureas in methanol.Efficient trapping of the diazocyclopropanes occurred in dilute solution with a slight excess of carbonyl compounds.The reactivity of the resulting 1-(α-hydroxyalkyl)cyclopropanediazonium ions (10) depended strongly on the α-substituents.Pinacol rearrangements predominated with aldehyde adducts, the migratory aptitudes being H > Ph > CH3.These 1,2-shifts are thought to proceed with inversion at the terminus - the preferred exo-attack of acetaldehyde at 7-diazonorcarane (38) led to the endo-ketone 40.The major product derived from the acetone adduct 22 was the epoxide 26 whose reaction(s) with metanol were also examined.The intramolecular addition of 8-diazobicyclooctan-4-one (57) gave rise to 6-methoxybicyclooct-4-en-1-ol (60).Due to steric constraints, the intermediate 58 underwent exclusive cyclopropyl-allyl transformations (otherwise a minor reaction).
- Kirmse, Wolfgang,Hellwig, Georg,Chiem, Pham van
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p. 1511 - 1524
(2007/10/02)
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- Chemistry of gem-Dihalocyclopropanes. XVII. Cyclopropylidene Incertion. Formation and Ring Opening of Bicyclobutan-2-olate
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Reactions of gem-dibromocyclopropanemethanol derivatives 3a-3e with methyllithium lead to allenic alcohols 4a-4h and products which derive from ring opening of an intermediate bicyclobutan-2-olate (17).The latter is formed by insertion of the respective cyclopropylidene into a C-H bond.Evidence for 17 was obtained from deuterium labelling experiments.This ring opening generally occurs by a carbanion mechanism, but in the case of 3d the intermediate bicyclobutanolate rearranged to the acyclic aldehyde 10, apparently by a thermal mechanism.The secondary alcohols 3f-3h reacted with methyllithium to give the corresponding allenes exclusively, which was also the case with ethers 3i-3l derived from the primary alcohols.
- Nilsen, Nils O.,Skattebol, Lars,Sydnes, Leiv K.
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p. 587 - 592
(2007/10/02)
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- Conformational Analysis of the Cyclopropylacyl, Oxiranylacyl, and Aziridinylacyl Radicals by Electron Spin Resonance Spectroscopy
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A series of ring-substituted cyclopropylacyl, oxiran-2-ylacyl, and aziridin-2-ylacyl radicals have been prepared principally by the reaction of photolytically generated t-butoxyl radicals with the corresponding aldehydes.The e.s.r. spectra show that the cyclopropylacyl ?-radicals exist in s-cis- and s-trans-conformations of approximately equal stability, in which the plane of the acyl group bisects the ring (as it does in the parent aldehyde), and simulation of the spectra through the region of intermediate rates of exchange show that the barrier to rotation is ca. 17.5 kJ*mol-1.The behaviour of the trans-2-ethoxycarbonylcyclopropylacyl and 2,2-dimethylcyclopropylacyl radicals is similar.The oxiranylacyl and trans-3-methyloxiranylacyl radicals exist in the same two conformations with a rather lower barrier, and the N-alkylaziridinylacyl radicals appear to have a lower barrier still.
- Davies, Alwyn G.,Sutcliffe, Roger
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p. 1483 - 1488
(2007/10/02)
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- Synthesis of Some Substituted Pyrrolidines from Cyclopropyl Carbonyl Compounds
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A series of alkyl and aryl cyclopropyl carbonyl compounds, when refluxed in N-methylformamide in the presence of magnesium chloride, gave variously substituted pyrrolidines.
- Blake, Keith W.,Gillies, Iain,Denney, Ronald C.
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p. 700 - 702
(2007/10/02)
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