- Photoinduced Diverse Reactivity of Diazo Compounds with Nitrosoarenes
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A diverse reactivity of diazo compounds with nitrosoarene in an oxygen-transfer process and a formal [2 + 2] cycloaddition is reported. Nitosoarene has been exploited as a mild oxygen source to oxidize an in situ generated carbene intermediate under visible-light irradiation. UV-light-mediated in situ generated ketenes react with nitosoarenes to deliver oxazetidine derivatives. These operationally simple processes exemplify a transition-metal-free and catalyst-free protocol to give structurally diverse α-ketoesters or oxazetidines.
- Roy, Sourav,Kumar, Gourav,Chatterjee, Indranil
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p. 6709 - 6713
(2021/09/08)
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- PRO-PERFUME COMPOSITIONS
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The present invention relates to a perfuming composition comprising at least two properfume compounds selected from the group consisting of a pro-perfume compound releasing a perfume compound upon exposure to light, a pro-perfume compound releasing a perf
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Page/Page column 46; 70
(2021/06/26)
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- Selective Formation of Functionalized α-Quaternary Malononitriles toward 5,5-Disubstituted Pyrrolopyrimidinones
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A modular, selective approach to complex α-tertiary substituted malononitriles is reported. The method takes advantage of β-ester-substituted α,α-dinitrile alkenes as highly reactive, chemoselective electrophiles for 1,4-additions with organometallic nucleophiles to produce functionally and sterically dense all-carbon quaternary centers. In the presence of a chiral ester auxiliary bearing an aromatic ring, the 1,4-addition occurs with good to excellent selectivity due to favorable cation-π interactions. The highly functionalized malononitriles represent versatile building blocks and can be applied toward efficient, highly selective syntheses of 5,5-disubstituted pyrrolopyrimidinones.
- Whitehead, Alan,Zhang, Yong,McCabe Dunn, Jamie,Sherer, Edward C.,Lam, Yu-Hong,Stelmach, John,Sun, Aaron,Shiroda, Melisa,Orr, Robert K.,Waddell, Sherman T.,Raghavan, Subharekha
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supporting information
p. 4448 - 4451
(2017/09/11)
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- The stereoselective synthesis of 2-aryl-2-hydroxybutanoic acid via menthyl chiral auxiliaries
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In the presence of titanium(IV) tetraethoxide ((EtO)4Ti), menthyl arylglyoxylates are prepared by transesterification of ethyl arylglyoxylates and natural (-)-(1R,2S,5R)-menthol. Using menthyl as a chiral auxiliary, the corresponding novel (R)-menthyl 2-aryl-2-hydroxybutanoates are synthesized by the addition of Et2Zn with menthyl arylglyoxylates. The structures of the products are characterized by IR and 1H- and 13C-NMR spectroscopy, mass spectrometry, and elemental analysis. The diastereoselectivities are analyzed by HPLC. The addition reactions are completed with good yields and high diastereoisomeric excess (de up to 95%), and, after hydrolysis, the (R)-2-aryl-2-hydroxybutanoic acids are obtained with high optical purities.
- Xiang, Ji-Ming,Li, Bao-Lin
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experimental part
p. 2015 - 2022
(2010/12/25)
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- Asymmetric synthesis of chiral α-keto esters via Grignard addition to oxalates
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While enroute to an asymmetric synthesis of the chlorine containing metabolite (-)-cryptosporiopsin an efficient and reliable asymmetric synthesis of chiral α-keto esters was required. These compounds can be conveniently generated in 51-84% yields via Gri
- MaGee, David I.,Mallais, Tammy C.,Eic, Marijanna
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p. 3177 - 3181
(2007/10/03)
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- Dimethylzinc-mediated addition of alkenylzirconocenes to α-keto and α-imino esters
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(Matrix presented) Hydrozirconation of alkynes followed by in situ transmetalation to dimethylzinc and 1,2-addition to activated ketones and N-diphenylphosphinoylimines leads to tertiary allylic alcohols and amines in high overall yield. With 8-phenylmenthol as the chiral auxiliary, si-face attack proceeds in good to excellent diastereoselectivities.
- Wipf, Peter,Stephenson, Corey R. J.
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p. 2449 - 2452
(2007/10/03)
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- Diatereoselectivity in the O-H Insertion Reactions of Rhodium Carbenoids Derived from Phenyldiazoacetates of Chiral Alcohols. Preparation of α-Hydroxy and α-Alkoxy Esters
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A series of phenyldiazoacetates 3 derived from enantiomerically pure alcohols ((-)-borneol, (+)-menthol, (-)-menthol, (-)-8-phenylmenthol, (-)-trans-2-phenylcyclohexanol, (+)-trans-2-phenyl-cyclohexanol, and (-)-10-(dicyclohexylsulfamoyl)-D-isoborneol) were prepared from the corresponding α-keto esters 1 by way of the tosylhydrazones 2.Rhodium(II)-catalyzed decomposition of the diazoacetates 3 in the presence of water or alcohols resulted in carbenoid O-H insertion reactions to give the corresponding 2-hydroxy- or 2-alkoxyphenylacetates in good yield, but with varying degrees of diastereoselectivity.A range of rhodium(II) and other metal catalysts were investigated, with rhodium(II) acetate and rhodium(II) acetamide giving the best results.The stereochemistry of the major diastereomer was proved in most cases by independent synthesis from a mandelic acid derivative of known configuration.Possible mechanisms are discussed.
- Aller, Enrique,Brown, David S.,Cox, Geoffrey G.,Miller, David J.,Moody, Christopher J.
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p. 4449 - 4460
(2007/10/02)
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- ELECTROCATALYTIC TRANSESTERIFICATION
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Transesterification took place electrocatalytically at mild conditions in cathodic compartment, on glassy carbon electrode, in acetonitrile solution of the mixture of ester and alcohol.
- Masumizu, Tatsuya,Nozawa, Koohei,Kawai, Ken-ichi,Nakajima, Shoichi
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- Chiral Induction in Photochemical Reactions, II - Regio- and Diastereoselectivity in the Oxetane Formation of Chiral Phenylglyoxylates with Electron Rich Olefins
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In the photochemical oxetane formation of chiral phenylglyoxylates with 3 high diastereoselectivities and lower regioselectivities are achieved with 1a and 1d.The lower regio- and diastereoselectivities observed with 1c, 1e, and 1g can be rationalized by the influence of the chiral alcohol on the conformation of the keto ester and on the different steric hindrances of the cis (face-position) or trans (edge-position) diradicals 5 or 7.In agreement with this model the differences of activation parameters obtained for the regio- and diastereoselectivities of 5b and 7b are discussed.By variation of the starting olefins we observed an increase of the diastereoselectivity of oxetane formation in the sequence 8 ca. 7 5 4, caused by increasing control of the cis-diradical (face-position).
- Koch, Hartmut,Scharf, Hans-Dieter,Runsink, Jan,Leismann, Hans
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p. 1485 - 1503
(2007/10/02)
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