- Titanium(IV) Chloride-Catalyzed Photoalkylation via C(sp3)-H Bond Activation of Alkanes
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Despite the sophistication of C-H functionalization as one of the most powerful tools in organic synthesis, methodology for performing hydrogen-atom transfer of unactivated alkanes remains rather scarce. Herein, we describe chlorine radical-catalyzed C(sp3)-H photoalkylation using titanium(IV) chloride via a ligand-to-metal charge transfer process. Enabled by the unique properties of this abundant metal salt, the reaction not only effected the coupling of various alkanes with radical acceptors but also was shown to be applicable to direct photoalkylation of aromatic ketones.
- Yamane, Mina,Kanzaki, Yamato,Mitsunuma, Harunobu,Kanai, Motomu
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supporting information
p. 1486 - 1490
(2022/03/01)
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- Development of a Scalable Lanthanide Halide/Quaternary Ammonium Salt System for the Nucleophilic Addition of Grignard Reagents to Carbonyl Groups and Application to the Synthesis of a Remdesivir Intermediate
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This manuscript describes the development and implementation of a scalable additive system, consisting of a lanthanide salt and a solubilizing quaternary ammonium salt, to improve the yield and robustness of the addition of an organomagnesium reagent to a
- Brak, Katrien,Bremner, W. Stacy,Brown, Angela M.,Chtchemelinine, Andrei,Heumann, Lars,Kerschen, James A.,Stevens, Andrew C.,Subotkowski, Witold,Vieira, Tiago,Wolfe, Lydia C.,Xu, Boran,Yu, Chia-Yun
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- Regiodivergent Hydroborative Ring Opening of Epoxides via Selective C-O Bond Activation
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A magnesium-catalyzed regiodivergent C-O bond cleavage protocol is presented. Readily available magnesium catalysts achieve the selective hydroboration of a wide range of epoxides and oxetanes yielding secondary and tertiary alcohols in excellent yields and regioselectivities. Experimental mechanistic investigations and DFT calculations provide insight into the unexpected regiodivergence and explain the different mechanisms of the C-O bond activation and product formation.
- Magre, Marc,Paffenholz, Eva,Maity, Bholanath,Cavallo, Luigi,Rueping, Magnus
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supporting information
p. 14286 - 14294
(2020/09/15)
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- Light-Mediated Formal Radical Deoxyfluorination of Tertiary Alcohols through Selective Single-Electron Oxidation with TEDA2+.
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The synthesis of tertiary alkyl fluorides through a formal radical deoxyfluorination process is described herein. This light-mediated, catalyst-free methodology is fast and broadly applicable allowing for the preparation of C?F bonds from (hetero)benzylic, propargylic, and non-activated tertiary alcohol derivatives. Preliminary mechanistic studies support that the key step of the reaction is the single-electron oxidation of cesium oxalates—which are readily available from the corresponding tertiary alcohols—with in situ generated TEDA2+. (TEDA: N-(chloromethyl)triethylenediamine), a radical cation derived from Selectfluor.
- Aguilar Troyano, Francisco José,Ballaschk, Frederic,Jaschinski, Marcel,?zkaya, Yasemin,Gómez-Suárez, Adrián
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supporting information
p. 14054 - 14058
(2019/11/11)
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- Triphosgene and DMAP as Mild Reagents for Chemoselective Dehydration of Tertiary Alcohols
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The utility of triphosgene and DMAP as mild reagents for chemoselective dehydration of tertiary alcohols is reported. Performed in dichloromethane at room temperature, this reaction is readily tolerated by a broad scope of substrates, yielding alkenes preferentially with the (E)-geometry. While formation of the Hofmann products is generally favored, a dramatic change in alkene selectivity toward the Zaitzev products is observed when the reaction is carried out in dichloroethane at reflux.
- Ganiu, Moshood O.,Cleveland, Alexander H.,Paul, Jarrod L.,Kartika, Rendy
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supporting information
p. 5611 - 5615
(2019/08/01)
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- On the effect of backbone modifications in 3,3-dimethyl-1-(trifluoromethyl)-3H-1λ3,2-benziodaoxole
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We report on the effect of small side-chain modifications to the structure of 3,3-dimethyl-1-(trifluoromethyl)-3H-1λ3,2-benziodaoxole (1b) on its reactivity, as expressed by the initial rate v0 in a model reaction, and show how the latter can be successfully correlated to an easily determined physical parameter p, a 13C NMR chemical shift. The relationship v0~ p is already present in the simplest starting material devoid of the hypervalent bond and the iodine core and, therefore, presents an interesting approach towards the future scaffold-optimization of this class of reagents. The reactivity of hypervalent-iodine-based trifluoromethylating agents, as expressed by the initial rate v0 in a model reaction, correlates to an easily determined physical parameter p, a 13C NMR chemical shift.
- Santschi, Nico,Matthey, Coraline,Schwenk, Rino,Otth, Elisabeth,Togni, Antonio
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supporting information
p. 1925 - 1931
(2015/03/18)
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- Radical pairs with rotational fluidity in the photochemical reaction of acetophenone and cyclohexane in the zeolite NAY: A 13C CPMAS NMR and product analysis study
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The photochemical reaction of acetophenone and cyclohexane in the zeolite NaY occurs by combination of the geminate radical pairs to give products that reveal a significant amount of rotational fluidity, which was also documented by intermolecular nuclear dipolar interaction measurements using cross polarization 13C NMR (CPMAS) experiments. The Royal Society of Chemistry 2009.
- Amboya, Ammee,Nguyen, Tina,Huynh, Hien T.,Brown, Ashley,Ratliff, Gretchen,Yonutas, Heather,Cizmeciyan, Deniz,Natarajan, Arunkumar,Garcia Garibay, Miguel A.
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experimental part
p. 2322 - 2326
(2009/09/26)
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- A new aspect of magnesium bromide-promoted enantio-selective aryl additions of triaryl(tetrahydrofuran)aluminum to ketones catalyzed by a titanium(IV) catalyst of trans-1,2-bis(hydroxycamphorsulfonylamino)cyclohexane
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A novel aspect of MgBr2-promoted asymmetric triarylaluminum- tetrahydrofuran [AlAr3 (THF)] additions to ketones catalyzed by a titanium catalyst of 20 mol% trans-1,2-bis(hydroxycamphorsulfonylamino) cyclohexane (2) is reported. The catalytic system works excellently for aromatic ketones with either an electron-withdrawing or an electrondonating substituent on the aromatic ring at the 2′-, 3′-, or 4′-positions, affording tertiary alcohols in excellent enantioselectivities of ≥90% ee, except for the cases of phenyl addition to 2′-methoxyacetophenone and 4-trimethylsilylphenyl (4-TMSC6H4) addition to acetopheneone.
- Chen, Chien-An,Wu, Kuo-Hui,Gau, Han-Mou
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scheme or table
p. 1626 - 1634
(2009/07/01)
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- Kinetic resolution of hydroperoxides with enantiopure phosphines: Preparation of enantioenriched tertiary hydroperoxides
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An efficient reductive kinetic resolution strategy capable of accessing optically active tertiary hydroperoxides is reported. Readily accessible tertiary hydroperoxides are resolved with commercially available (R)- or (S)-xylyl-PHANEPHOS with selectivity factors as large as 37. The resulting bis(phosphine oxide) can be recycled in high yields. The isolated mono(phosphine oxide) intermediate resolved hydroperoxides with the same selectivity as the parent bisphosphine. Copyright
- Driver, Tom G.,Harris, Jason R.,Woerpel
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p. 3836 - 3837
(2008/02/13)
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- Semisynthetic enzymes in asymmetric synthesis: Enantioselective reduction of racemic hydroperoxides catalyzed by seleno-subtilisin
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The serine protease subtilisin was chemically converted into the peroxidase-active seleno-subtilisin. This semisynthetic enzyme catalyzes the enantioselective reduction of racemic hydroperoxides in the presence of thiophenols to yield optically active hydroperoxides and alcohols on the semipreparative scale. The kinetic parameters and enantioselectivities of seleno-subtilisin-catalyzed reduction of various chiral hydroperoxides were determined. The catalytic efficiency of this semisynthetic enzyme is comparable to that of the native horseradish peroxidase. The sense in the enantioselectivity of the seleno-subtilisin is opposite to the natural enzymes previously used in the synthesis of optically active hydroperoxides. Consequently, the semisynthetic enzyme selenosubtilisin complements the naturally available peroxidases for the asymmetric synthesis of both enantiomers.
- Haering, Dietmar,Schueler, Ellen,Adam, Waldemar,Saha-Moeller, Chantu R.,Schreier, Peter
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p. 832 - 835
(2007/10/03)
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- [(3-dimethylamino)propyl]dimethylaluminum: A convenient reagent for methylation and ethynylation of carbonyl compounds
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At 60-80°C the title compound methylates a variety of mono- and diketones. Aromatic aldehydes undergo simple methylation by the reagent only after initial treatment with an equivalent amount of AlCl3. Upon reaction of Me2Al(CH2)3NMe2 with terminal acetylenes the aluminum complex is converted into a carbonyl-alkynylation reagent.
- Baidossi, Wael,Rosenfeld, Ayelet,Wassermann, Brigit C.,Schutte, Stefan,Schumann, Herbert,Blum, Jochanan
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p. 1127 - 1130
(2007/10/03)
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- Samarium(II) triflate as a new reagent for the grignard-type carbonyl addition reaction
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On treatment of a THF solution of Sm(OTf)3 with 1 equiv of an organolithium or organomagnesium reagent at ambient temperature, the purple or deep green solution of the divalent samarium triflate [Sm(OTf)2] was readily obtained. For this preparation, s-BuLi was the most effective as was evidenced by the reduction of 2-phenylethyl iodide in the presence of HMPA. The Sm(OTf)2 reagent mediated the Grignard-type reaction effectively in THF/HMPA; alkylation and allylation of ketones or aldehydes with alkyl, allyl, or benzyl halides proceeded via organosamarium intermediates. Diastereoselectivity of the samarium-Grignard reaction was examined using 2-methylcyclohexanone, 4-tert-butylcyclohexanone, and 2-phenylpropanal and was found to be higher in each case than that with SmI2. With 2-methylcyclohexanone, for example, Sm(OTf)2 gave the greatest ratio of axial alcohol:equatorial alcohol = 99:1, and SmI2 gave a ratio of 91:9. Halides containing an ester or a silyl group were reactive in the Reformatsky- or Peterson-type reaction, respectively, using the Sm(OTf)2 reagent.
- Fukuzawa, Shin-Ichi,Mutoh, Keisuke,Tsuchimoto, Teruhisa,Hiyama, Tamejiro
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p. 5400 - 5405
(2007/10/03)
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- The samarium grignard reaction. In situ formation and reactions of primary and secondary alkylsamarium(III) reagents
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This work shows that primary and secondary radicals are rapidly reduced in THF/HMPA to form primary- and secondary-alkylsamarium reagents. The primary- and secondary-radicals can be formed either by direct SmI2 reduction of primary- and secondary-halides or by a previous rapid radical cyclization. The samarium reagents have moderate stability in solution, and they react with a variety of typical electrophiles, including aldehydes and ketones. The work further shows that organosamarium intermediates can be involved in the traditional samarium Barbier reaction of aldehydes and ketones conducted in THF/HMPA. A new procedure called the "samarium Grignard" method is introduced, and it is suggested that this new procedure will have considerably more scope and generality than the samarium Barbier reaction.
- Curran, Dennis P.,Totleben, Michael J.
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p. 6050 - 6058
(2007/10/02)
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- Substituent Effect on the Enantioface-Differentiating Reaction of (R)- with m- or p-Substituted Acetophenones
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When lithiomethyl p-tolyl sulfoxide derived from (R)-(+)- was allowed to react with acetophenones which have a variety of m- or p-substituents, the corresponding diastereomeric mixture of β-hydroxy sulfoxides (RSSC and RSRC) was produced.The degree of enantioselectivity was affected by the nature of the substituent on benzene ring.The logarithms of RSSC/RSRC values thus obtained gave a good correlation with Hammett's ? values, affording a negative straight line.The results have been discussed in view of the stereochemical course of the reaction.
- Kunieda, Norio,Nokami, Junzo,Kinoshita, Masayoshi
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p. 526 - 529
(2007/10/02)
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- AZO ANIONS IN SYNTHESIS. USE OF TRITYL- AND DIPHENYL-4-PYRIDYLMETHYLHYDRAZONES FOR REDUCTIVE C-C BOND FORMATION.
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The lithium salts of trityl- and diphenyl-4-pyridylmethyl-hydrazones of both aldehydes and ketones react with electrophiles (alkyl halides, aldehydes, ketones, crotonates) at low temperature to form C-trapped azo compounds; these intermediates decompose homolytically with loss of nitrogen below room temperature and can be diverted in a synthetically useful way to alkanes, alkenes, alcohols or saturated esters.
- Baldwin, Jack E.,Adlington, Robert M.,Bottaro, Jeffrey C.,Kolhe, Jayant N.,Newington, Ian M.,Perry, Matthew W. D.
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p. 4235 - 4246
(2007/10/02)
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- Sulfoximine-Mediated Syntheses of Optically Active Alcohols
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Optically active β-hydroxy sulfoximines were prepared, as diastereomeric pairs, by the addition the lithium derivative of optically active N,S-dimethyl-S-phenylsulfoximine to prochiral ketones and aldehydes.The ketone adducts after separation by medium-pr
- Johnson, Carl R.,Stark, Charles J.
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p. 1193 - 1196
(2007/10/02)
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