- Bi(cyclopentyl)diol-Derived Boronates in Highly Enantioselective Chiral Phosphoric Acid-Catalyzed Allylation, Propargylation, and Crotylation of Aldehydes
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In this study, we disclose the catalytic addition of bi(cyclopentyl)diol-derived boronates to aldehydes promoted by chiral phosphoric acids, allowing for the formation of enantioenriched homoallylic, propargylic, and crotylic alcohols (up to >99% enantiom
- Yuan, Jinping,Jain, Pankaj,Antilla, Jon C.
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p. 12988 - 13003
(2020/11/23)
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- Design and synthesis of new alkyl-based chiral phosphoric acid catalysts
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Using chiral BINOL-derived phosphoric acids (PA's) to activate substrates for enhanced reactivity is now regarded as a powerful strategy to control enantioselectivity in asymmetric synthesis. Generally, most substituents at the 3,3′-positions of BINOL PA'
- Tang, Xiaoxue,He, Hualing,Fang, Xiantao,Chang, Zexu,Antilla, Jon C.
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supporting information
p. 592 - 602
(2019/06/24)
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- Enantioselective 1,2-Anionotropic Rearrangement of Acylsilane through a Bisguanidinium Silicate Ion Pair
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Highly enantioselective bisguanidinium-catalyzed tandem rearrangements of acylsilanes are reported. The acylsilanes were activated via an addition of fluoride on the silicon to form a penta-coordinate anionic silicate intermediate. The silicate then underwent alkyl or aryl group migration from the silicon atom to the neighboring carbonyl carbon atom (1,2-anionotropic rearrangement), followed by [1,2]-Brook rearrangement to provide the secondary alcohols in high yields with excellent enantioselectivities (up to 95% ee). The isolation of an α-silylcarbinol intermediate as well as DFT calculations revealed that the 1,2-anionotropic rearrangement occurred via a bisguanidinium silicate ion pair, which is the stereodetermining step. The chiral center formed is then retained without inversion through the subsequent [1,2]-Brook rearrangement. Crotyl acylsilanes were smoothly transformed into homoallylic linear crotyl alcohols with retention of E/Z geometry, and no branched alcohols were detected. This clearly suggested that the 1,2-anionotropic rearrangement occurred through a three-membered instead of a five-membered transition state.
- Cao, Weidi,Tan, Davin,Lee, Richmond,Tan, Choon-Hong
-
supporting information
p. 1952 - 1955
(2018/02/17)
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- Enantioselective Allyl-, and Allenylboration of Aldehydes Catalyzed by Chiral Hydroxyl Carboxylic Acid
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Asymmetric allylboration of aldehydes with allylboronic acid pinacol ester catalyzed by chiral hydroxyl carboxylic acid is described. This reaction provides synthetically useful homoallyl alcohols in high yield with good to high enantioselectivity. The pr
- Ota, Yuya,Kawato, Yuji,Egami, Hiromichi,Hamashima, Yoshitaka
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supporting information
p. 976 - 980
(2017/05/05)
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- Asymmetric Allylation of Carbonyl Compounds Catalyzed by a Chiral Phosphine–Silver Complex
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A catalytic, asymmetric allylation reaction of aldehydes or ketones with allyltrimethoxysilane was achieved by using a BINAP·AgBF4 [BINAP = 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl] complex as the chiral precatalyst and triethylamine as the
- Yanagisawa, Akira,Yang, Nan,Bamba, Kentaro
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supporting information
p. 6614 - 6618
(2017/12/15)
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- A chiral bipyridyl alcohol for catalytic enantioselective Nozaki-Hiyama-Kishi allylation of aldehydes and ketones
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A class of bipyridyl alcohol ligands has been developed. A catalyst synthesized using a chromium(II)-ligand promotes the enantioselective Nozaki-Hiyama-Kishi (NHK) allylation of aldehydes and ketones with allylic halides. The allylation of various aromati
- Chen, Rui-Yu,Dhondge, Attrimuni P.,Lee, Gene-Hsian,Chen, Chinpiao
-
supporting information
p. 961 - 966
(2015/03/30)
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- Protecting-group-free diastereoselective C-C coupling of 1,3-glycols and allyl acetate through site-selective primary alcohol dehydrogenation
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Safe from protection! A pronounced kinetic preference for primary alcohol dehydrogenation enables the site-selective iridium catalyzed C-C coupling of polyols with allyl acetate in the absence of protecting groups, premetallated reagents, chiral auxiliaries, and discrete alcohol-to-aldehyde oxidation.
- Dechert-Schmitt, Anne-Marie R.,Schmitt, Daniel C.,Krische, Michael J.
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supporting information
p. 3195 - 3198
(2013/04/24)
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- Br?nsted acid-catalyzed asymmetric allylation and propargylation of aldehydes
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A method synthesizing homoallylic or homopropargylic alcohols was developed to react aldehydes with allyl boronates, such as allylboronic acid pinacol ester, or allenylborates in the presence of a catalytic amount of a chiral binaphthyl-derived chiral pho
- -
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Page/Page column 8; 21; 22
(2013/08/28)
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- Conformationally rigid chiral pyridine N-oxides as organocatalyst: Asymmetric allylation of aldehydes
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A pyridine unit with a conformationally rigid chiral backbone has been designed and synthesized in an enantiomerically pure form to utilize in the Lewis base-catalyzed Sakurai-Hosomi-Denmark-type allylation reaction. The chiral pyridine N-oxide in 1:1 mix
- Gnanamani, Elumalai,Someshwar, Nagamalla,Ramanathan, Chinnasamy Ramaraj
-
supporting information
p. 2101 - 2106
(2012/11/07)
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- Chiral biscarboline N,N′-dioxide derivatives: Highly enantioselective addition of allyltrichlorosilane to aldehydes
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The allylation of aromatic and aliphatic aldehydes with allyltrichlorosilanes has been catalyzed with a new Lewis base organocatalyst, 1,1′-biscarboline N,N′-dioxide with high enantioselectivities of up to 99% for 4-methoxybenzaldehyde and 97% ee for cycl
- Bai, Bing,Shen, Lan,Ren, Jie,Zhu, Hua Jie
-
supporting information; experimental part
p. 354 - 358
(2012/04/10)
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- Structure influence of chiral 1,1′-biscarboline-N,N′-dioxide on the enantioselective allylation of aldehydes with allyltrichlorosilanes
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A series of new axially chiral 1,1′-biscarboline-N,N′-dioxide Lewis base organocatalysts were examined in the asymmetric allylation of aldehydes with allyltrichlorosilane. The chiral catalysts (R)-1a-e bearing ester groups in 3,3′ position provided good y
- Bai, Bing,Zhu, Hua-Jie,Pan, Wei
-
experimental part
p. 6829 - 6836
(2012/08/28)
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- A pineno-salen type catalyst for the enantioselective Nozaki-Hiyama-Kishi reaction
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A new class of pineno-salen type ligands 10, 11, 17, 20, 23, and 24 has been developed. The catalyst formed from chromium(II)-10 promotes the enantioselective Nozaki-Hiyama-Kishi allylation of alkyl and aryl aldehydes using allyl bromide. Notably, the asymmetric addition of vinyl halide to benzaldehyde was achieved with 24% ee.
- Dhondge, Attrimuni P.,Shaikh, Ajam C.,Chen, Chinpiao
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p. 723 - 733
(2012/08/29)
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- Asymmetric allylboration of aldehydes with pinacol allylboronates catalyzed by 1,1′-spirobiindane-7,7′-diol (SPINOL) based phosphoric acids
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The asymmetric allylboration of aldehydes with pinacolallylboronates catalyzed by 1,1′-spirobiindane-7,7′-diol (SPINOL) based phosphoric acids is described. 6,6′-Bis(2,4,6-triisopropylphenyl)SPINOL-based phosphoric acid was found to be a general, highly e
- Xing, Chun-Hui,Liao, Yuan-Xi,Zhang, Yimei,Sabarova, Darya,Bassous, Monica,Hu, Qiao-Sheng
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supporting information; experimental part
p. 1115 - 1118
(2012/04/10)
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- C2-symmetrical bipyridyldiols as promising enantioselective catalysts in Nozaki-Hiyama allylation
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Several new chiral bipyridyldiol ligands that promote the chromium-catalyzed enantioselective addition of allylic halides to aldehydes in up to 99% ee were synthesized. The chromium-catalyzed allylation of aldehydes using ligands 4 and 4a in the presence
- Huang, Xin-Ren,Pan, Xin-Hong,Lee, Gene-Hsian,Chen, Chinpiao
-
supporting information; experimental part
p. 1949 - 1954
(2011/10/13)
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- Synthesis of (-)-viriditoxin: A 6,6′-binaphthopyran-2-one that targets the bacterial cell division protein FtsZ
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(Chemical Equation Presented) Remote control: Vanadium catalysts provide the key to synthesizing the bacteria-fighting natural product viriditoxin. An achiral catalyst shows modest levels of remote diastereocontrol induced by the lactone stereogenic center and chiral catalysts can be used to enhance or reverse this inherent selectivity.
- Park, Young Sam,Grove, Charles I.,Gonzalez-Lopez, Marcos,Urgaonkar, Sameer,Fettinger, James C.,Shaw, Jared T.
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supporting information; experimental part
p. 3730 - 3733
(2011/05/15)
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- Indium-mediated asymmetric Barbier-type allylations: Additions to aldehydes and ketones and mechanistic investigation of the organoindium reagents
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(Chemical Equation Presented) We report a simple, efficient, and general method for the indium-mediated enantioselective allylation of aromatic and aliphatic aldehydes and ketones under Barbier-type conditions in a one-pot synthesis affording the corresponding chiral alcohol products in very good yield (up to 99%) and enantiomeric excess (up to 93%). Our method is able to tolerate various functional groups, such as esters, nitriles, and phenols. Additionally, more substituted allyl bromides, such as crotyl and cinnamyl bromide, can be used providing moderate enantioselectivity (72% and 56%, respectively) and excellent diastereoselectivity when employing cinnamyl bromide (95/5 anti/syn). However, the distereoselectivity when using crotyl bromide was poor and other functionalized allyl bromides under our method afforded low enantioselectivities for the alcohol products. In these types of indium-mediated additions, solvent plays a major role in determining the nature of the organoindium intermediate and we observed the susceptibility of some allylindium intermediates to hydrolysis in protic solvents. Under our reaction conditions using a polar aprotic solvent, we suggest that an allylindium(III) species is the active allylating intermediate. In addition, we have observed the presence of a shiny, indium(0) nugget throughout the reaction, irrespective of the stoichiometry, indicating disproportionation of indium halide byproduct formed during the reaction.
- Haddad, Terra D.,Hirayama, Lacie C.,Singaram, Bakthan
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supporting information; experimental part
p. 642 - 649
(2010/04/29)
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- Chiral bronsted acid-catalyzed allylboration of aldehydes
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The catalytic enantioselective allylation of aldehydes is a long-standing problem of considerable interest to the chemical community. We disclose a new high-yielding and highly enantioselective chiral Bronsted acid-catalyzed allylboration of aldehydes. Th
- Jain, Pankaj,Antilla, Jon C.
-
supporting information; experimental part
p. 11884 - 11886
(2010/11/17)
-
- Simple and fast synthesis of new axially chiral bipyridine N, N'-dioxides for highly enantioselective allylation of aldehydes
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Unsymmetrically 3,3'-substituted axially chiral bis(tetrahydroisoquinoline) N,N'-dioxides can be prepared in just three steps. They exhibit unique catalytic activity (turnover frequency, enantioselectivity, substrate scope) in the asymmetric allylation of
- Kadlcikova, Aneta,Hrdina, Radim,Valterova, Irena,Kotora, Martin
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supporting information; experimental part
p. 1279 - 1283
(2009/12/22)
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- Catalytic asymmetric allylation of aliphatic aldehydes by chiral bipyridine N,N′-dioxides
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A new class of axially chiral bipyridine N,N′-oxides with bis(tetrahydroisoquinoline) framework were tested as catalysts in the reaction of aliphatic aldehydes with allyl(trichloro)silane to afford homoallylic alcohols. The course of the reaction, that is
- Hrdina, Radim,Boyd, Thomas,Valterová, Irena,Hoda?ová, Jana,Kotora, Martin
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experimental part
p. 3141 - 3144
(2009/06/17)
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- Catalytic enantioselective allyl- and crotylboration of aldehydes using chiral diol·SnCl4 complexes. Optimization, substrate scope and mechanistic investigations
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We report a novel class of C2-symmetric chiral diols derived from the hydrobenzoin skeleton. The combination of these diols with SnCl 4 under Yamamoto's concept of Lewis acid assisted Bronsted acidity (LBA catalysis) leads to high levels of asymmetric induction in the allylboration of aldehydes by commercially available allylboronic acid pinacol ester 1a. The corresponding homoallylic alcohol products of synthetically useful aliphatic aldehydes are obtained in excellent yields with up to 98:2 er. This combined acid manifold is also efficient in catalyzing the diastereo- and enantioselective crotylboration of aldehydes, thus providing the propionate units in >95:5 dr and up to 98:2 er. The X-ray crystal structure of the optimal diol·SnCl4 complex, Vivol (4m)·SnCl 4, unambiguously shows the Bronsted acidic character of this LBA catalyst and its highly dissymmetrical environment. Further controls have ruled out a possible boron transesterification mechanism with the chiral diol and point to LBA catalyst-derived activation of the pinacol allylic boronates 1. Due to slow dissociation of the diol·SnCl4 complex, a small excess of diol is required in order to suppress a competing racemic cycle catalyzed by free SnCl4.
- Rauniyar, Vivek,Zhai, Huimin,Hall, Dennis G.
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supporting information; scheme or table
p. 8481 - 8490
(2009/02/02)
-
- STABLE BORANE REAGENTS AND METHODS FOR THEIR USE
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The invention provides methods for storing boranes (e.g. B-allyldiisopinocampheylborane). The invention also provides stable compositions comprising boranes, as well as methods for carrying out allylboration at high temperature and/or in the presence of w
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Page/Page column 4
(2008/12/09)
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- Asymmetric allylation of aldehydes with allyltrichlorosilane using aza-paracyclophane-oxazoline-N-oxide catalysts
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Novel aza-paracyclophane-oxazoline catalysts 4, 5 were produced from V?gtle's Rp-2-cyano-aza-paraclycophane and amino alcohols reacted with zinc chloride followed by m-chloroperbenzoic acid. 4′-Benzyl and tert-butyl-S and R-oxazoline variants w
- Chai, Qiang,Song, Chun,Sun, Zhijun,Ma, Yudao,Ma, Chanqin,Dai, Yong,Andrus, Merritt B.
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p. 8611 - 8615
(2007/10/03)
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- Catalytic enantioselective and catalyst-controlled diastereofacial- selective additions of allyl- and crotylboronates to aldehydes using chiral Bronsted acids
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(Chemical Equation Presented) Towards the ideal: A chiral diol-SnCl 4 complex is applied to the allylboration of aldehydes (see scheme). This approach highlights the use of chiral Bronsted acid catalysis in the development of an ideal method for the allylation of aldehydes which would display high diastereo- and enantioselectivity, wide substrate scope, and high practicality (ease of use, low cost, and low environmental impact).
- Rauniyar, Vivek,Hall, Dennis G.
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p. 2426 - 2428
(2007/10/03)
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- Application of tridentate bis(oxazoline) ligands in catalytic asymmetric Nozaki-Hiyama allylation and crotylation: An example of high enantioselection with a non-symmetric bis(oxazoline) ligand
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A series of both symmetric and non-symmetric bis(oxazoline) ligands was applied in the Nozaki-Hiyama allylation and crotylation of benzaldehyde. It was found that both the magnitude and sense of the asymmetric induction depended strongly on the nature and
- McManus, Helen A.,Cozzi, Pier Giorgio,Guiry, Patrick J.
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p. 551 - 558
(2007/10/03)
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- Catalytic asymmetric allylation of aldehydes using the chiral (salen)chromium(III) complexes
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The enantioselective addition of allylstannanes to glyoxylates and glyoxals, as well as simple aromatic and aliphatic aldehydes, catalyzed by chiral (salen)Cr(III) complexes, has been studied. The reaction proceeded smoothly for the reactive 2-oxoaldehydes and allyltributyltin in the presence of small amounts (1-2 mol %) of (salen)Cr(III)BF4 (1b) under mild, undemanding conditions. However, in the case of other simple aldehydes, the use of high-pressure conditions is required to obtain good yields. Classic chromium catalyst 1b, easily prepared from the commercially available chloride complex 1a, affords homoallylic alcohols usually in good yield and with enantiomeric purity of 50-79% ee. The stereochemical results are rationalized on the basis of the proposed model.
- Kwiatkowski, Piotr,Cha?adaj, Wojciech,Jurczak, Janusz
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p. 5116 - 5125
(2007/10/03)
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- Catalytic enantioselective Nozaki-Hiyama allylation reaction with tethered bis(8-quinolinolato) (TBOx) chromium complex
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The utility of the new class of chiral ligand, tethered bis(8-quinolinol) (TBOxH), is further explored. Its chromium complex, TBOxCr(III)Cl, effectively catalyzes the Nozaki-Hiyama allylation reactions of various aldehydes at room temperature with high yield (up to 95%) and high enantioselectivity (up to 99% ee). The scope of the present method is shown to be wide, and this method represents an efficient access to chiral homoallylic alcohols. Copyright
- Xia, Guoyao,Yamamoto, Hisashi
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p. 2554 - 2555
(2007/10/03)
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- Indium-mediated Barbier-type allylation of aldehydes as a convenient method for the highly enantioselective synthesis of homoallylic alcohols
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We report a general method for the indium-mediated Barbier-type enantioselective allylation of both aromatic and aliphatic aldehydes using commercially available (1S,2R)-(+)-2-amino-1,2-diphenylethanol as a chiral auxiliary. Using only two equivalents of allyl bromide, excellent yields and very good to excellent enantioselectivities are obtained. To our knowledge, the enantioselectivities reported herein are the highest obtained for indium-promoted allylations of carbonyl compounds.
- Hirayama, Lacie C.,Gamsey, Soya,Knueppel, Daniel,Steiner, Derek,Delatorre, Kelly,Singaram, Bakthan
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p. 2315 - 2318
(2007/10/03)
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- Stereochemical diversity in chiral ligand design: Discovery and optimization of catalysts for the enantioselective addition of allylic halides to aldehydes
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(Chemical Equation Presented) We have identified a new set of stereochemically diverse oxazoline ligands derived from simple amino acids that promote the Cr-catalyzed enantioselective addition of allylic halides to aldehydes in up to 95% ee. The Cr-cataly
- Lee, Jae-Young,Miller, Jeremie J.,Hamilton, Steven S.,Sigman, Matthew S.
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p. 1837 - 1839
(2007/10/03)
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- High-pressure enantioselective allylation of aldehydes catalyzed by (salen)chromium(III) complexes
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The enantioselective addition of allyltributyltin to simple aldehydes (2a-1), catalyzed by chiral (salen)Cr(III) complexes 1, has been studied. The reaction proceeds smoothly with low loading (1-2 mol%) of (salen)Cr(III)BF 4 (1a) and allyltribu
- Kwiatkowski, Piotr,Jurczak, Janusz
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p. 227 - 230
(2007/10/03)
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- A sterically modified (salen)chromium(III) complex - An efficient catalyst for high-pressure asymmetric allylation of aldehydes
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A novel (salen)chromium(III) catalyst with a modified salen ligand was synthesised in a simple way starting from readily available precursors. High-pressure allylation reaction of aromatic and aliphatic aldehydes with allyltributyltin upon application of
- Kwiatkowski, Piotr,Cha?adaj, Wojciech,Jurczak, Janusz
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p. 2301 - 2304
(2007/10/03)
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- Catalytic asymmetric allylation of aldehydes via a chiral indium(III) complex
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A chiral indium complex has been discovered to effect high enantioselectivities in the addition of allyltributyl stannanes to aldehydes. The allylation of a variety of aromatic, α,β-unsaturated and aliphatic aldehydes resulted in good yields and high enantioselectivities (90-96% ee). The Royal Society of Chemistry 2005.
- Teo, Yong-Chua,Tan, Kui-Thong,Loh, Teck-Peng
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p. 1318 - 1320
(2008/09/16)
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- A highly efficient and practical new allylboronate tartramide for the asymmetric allylboration of achiral aldehydes
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Chiral homoallylic alcohols can be prepared from aldehydes upon reaction with two optically pure allylboronate tartramides. The enantiomeric excess is 10-15% higher for the allylation of benzaldehyde when using N,N'-dibenzyl-tartramide auxiliary 5b than when using N,N'-diphenyl-tartramide (5a). 2-Allyl-N,N'-dibenzyl-1,3,2-dioxaborolane-4,5-dicarbamide (2b) affords homoallylic alcohols with 90-99% ee upon reaction with some representative aldehydes. The derivatised chiral auxiliaries can be recovered by simple recrystallization, in 85% yield, without any loss of specific rotation. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.
- Chen, Wansuo,Liu, Yanzhu,Chen, Zhirong
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p. 1665 - 1668
(2007/10/03)
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- Asymmetric allylboration of aldehydes and ketones using 3,3′-disubstitutedbinaphthol-modified boronates
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Allylboronates derived from 3,3′-disubstituted 2,2′-binaphthols react with aldehydes and ketones to give the expected allylated products with up to >99:1 er. Highest selectivities were observed for aromatic ketones. The bis(trifluoromethyl) derivative is particularly outstanding in terms of reactivity, selectivity, and robustness.
- Wu, T. Robert,Shen, Lixin,Chong, J. Michael
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p. 2701 - 2704
(2007/10/03)
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- Scope and limitations of the scandium-catalyzed enantioselective addition of chiral allylboronates to aldehydes
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Scandium triflate catalyzes the addition of camphor-derived allyl-, methallyl-, and crotylboronates to aldehydes to provide homoallylic alcohols with excellent diastereo- and enantioselectivity. Aromatic, aliphatic, and propargylic aldehydes can be used successfully in this system. Additional advantages of the camphor-diol allylboronates are their ease of synthesis, their availability in both enantiomeric forms, and their stability towards silica gel chromatography. The usefulness of this methodology is further demonstrated by the gram-scale synthesis of various homoallylic alcohols of high enantiomeric excess and by the concise synthesis of the pheromone (4S)-2-methyloctan-4-ol. 1 Introduction 2 Results and Discussion 2.1 Optimization 2.2 Substrate Scope 2.3 Synthetic Applications 2.4 Mechanistic Considerations 3 Conclusion.
- Gravel, Michel,Lachance, Hugo,Lu, Xiaosong,Hall, Dennis G.
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p. 1290 - 1302
(2007/10/03)
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- A highly enantioselective allyl-transfer through suppression of epimerization
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A highly enantioselective allyl transfer method was successfully developed, producing terminal homoallylic alcohols in moderate to high yields. In all cases, reactions were carried out under mild acid conditions; reducing the reaction temperature suppressed racemization.
- Lee, Cheng-Hsia Angeline,Loh, Teck-Peng
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p. 5819 - 5822
(2007/10/03)
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- Novel Lewis acid-assisted chiral Lewis acid (LLA) system: Development of boroxin-Ti-BINOL-catalyzed asymmetric allylation of aldehydes
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The formation of hetero multimetallic complex having B-O-Ti bond could increase the Lewis acidity of titanium. A novel LLA system made up of Ti-BINOL and 4-(trifluoromethyl)phenyl-boroxin dramatically accelerated the allylation reaction of aldehyde with h
- Xia, Guoyao,Shibatomi, Kazutaka,Yamamoto, Hisashi
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p. 2437 - 2439
(2007/10/03)
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- Asymmetric catalysis of Nozaki-Hiyama allylation and methallylation with a new tridentate bis(oxazolinyl)carbazole ligand
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This work describes the development of a new tridentate ligand effective for the asymmetric catalysis of Nozaki-Hiyama allylation and methallylation. Various aldehydes were allylated or methallylated with good enantioselectivity (86-96%), and a key interm
- Inoue, Masahiro,Suzuki, Takahiro,Nakada, Masahisa
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p. 1140 - 1141
(2007/10/03)
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- BINAP/AgOTf/KF/18-crown-6 as new bifunctional catalysts for asymmetric Sakurai-Hosomi allylation and Mukaiyama aldol reaction
-
A catalytic amount of KF·18-crown-6 complex is effective as a soluble fluoride source to activate an asymmetric Sakurai-Hosomi allylation with BINAP and silver(I) triflate catalyst. The allylation of a variety of aromatic, α,β-unsaturated and aliphatic al
- Wadamoto, Manabu,Ozasa, Nobuko,Yanagisawa, Akira,Yamamoto, Hisashi
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p. 5593 - 5601
(2007/10/03)
-
- A highly practical and enantioselective reagent for the allylation of aldehydes
-
Strain at silicon is the key to success of reagent 1 since this strain, which is induced by the diazasilacyclopentane ring, determines its reactivity. This practical and general new reagent for the highly enantioselective allylation of aldehydes is easily prepared as an air-stable solid and may be stored without significant decomposition.
- Kubota, Katsumi,Leighton, James L.
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p. 946 - 948
(2007/10/03)
-
- Strained silacycles in organic synthesis: A new reagent for the enantioselective allylation of aldehydes
-
A new reagent for the enantioselective allylation of aliphatic aldehydes has been developed. The reagent is easily prepared in a single step from commercially available materials and may be stored without significant decomposition. The reactivity of the r
- Kinnaird, James W. A.,Ng, Pui Yee,Kubota, Katsumi,Wang, Xiaolun,Leighton, James L.
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p. 7920 - 7921
(2007/10/03)
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- Optically pure α-(trimethylsilyl)benzyl alcohol: A practical chiral auxiliary for oxocarbenium ion reactions
-
(matrix presented) Enantiopure (S)-α-(trimethylsilyl)benzyl alcohol (98% ee) was prepared by Noyori's transfer hydrogenation of benzoyltrimethylsilane. The corresponding trimethylsilyl ether was subjected to Marko's silyl modified Sakurai conditions with
- Cossrow, Jennifer,Rychnovsky, Scott D.
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p. 147 - 150
(2007/10/03)
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- A one-pot conversion of carboxylic acids into homoallylic alcohols
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A one-pot procedure for the conversion of carboxylic acids into homoallylic alcohols under remarkably mild and selective conditions is described. The triethylammonium salts of alkanoic acids are treated with Bu3P/PhSeCl to afford the correspond
- Ollivier,Panchaud,Renaud
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p. 1573 - 1578
(2007/10/03)
-
- Enantioselective catalytic addition of allyl organometallic reagents to aldehydes promoted by [Cr(Salen)]: The hidden role played by weak Lewis acids in metallo-Salen promoted reactions
-
In this paper, we present the data obtained from kinetic analysis and from NLE study in the [Cr(Salen)] catalysed addition of allyl halides to aldehydes. The results show the key role played by weak Lewis acids in the catalytic system. Weak Lewis acids such as manganese salts and the [Cr(Salen)X] complex drive the stereochemistry of the reaction toward a high level of diastero- and enantioselectivity. Therefore, the Lewis acids and their properties must be taken into account in the rational design of metallo-Salen mediated processes.
- Bandini, Marco,Cozzi, Pier Giorgio,Umani-Ronchi, Achille
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p. 835 - 843
(2007/10/03)
-
- Synthesis and characterization of new enantiopure 7,7'-disubstituted 2,2'-dihydroxy-1,1'-binaphthyls: Useful ligands for the asymmetric allylation reaction of aldehydes
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As an extension of our interest in developing new enantioselective reactions based on the binaphthol privileged ligand, we report a simple approach to the synthesis of 7,7'-disubstituted binaphthols. The commercially available 1,7-dihydroxynaphthalene (1) was used as starting material for the preparation of the bromoderivatives 2, which were oxidatively coupled to afford 3, a key intermediate for the preparation of a variety of enantiopure substituted binaphthols (8, 10). The absolute configuration of the new compounds was established by chiroptical analysis and by cholesteric induction. The optically active catalysts derived from the ligands 3, 8, 10, 16 and 17, complexed with Ti(OiPr)2Cl2, Zr(OiPr)4 and ZrCl4(THF)2, were employed for the enantioselective addition of allyltributyltin to aldehydes. Finally, the influence of the substituent of the binaphthyl core on the transmission of the chiral information was also investigated.
- Bandin, Marco,Casolari, Sonia,Cozzi, Pier Giorgio,Proni, Gloria,Schmohelz, Erick,Spada, Gian Piero,Tagliavini, Emilio,Umani-Ronchi, Achille
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p. 491 - 497
(2007/10/03)
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- The first catalytic enantioselective Nozaki-Hiyama reaction
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The Nozaki-Hiyama reaction can be performed in an enantioselective catalytic way! The catalytic system utilizes 10 mol % of an inexpensive chiral [Cr(salen)] complex. The [Cr(salen)]/Mn/Me3SiCl system effectively promotes the enantioselective addition of allyl chloride to aliphatic and aromatic aldehydes at room temperature (65-89% ee, 40-60% yield).
- Bandini, Marco,Cozzi, Pier Giorgio,Melchiorre, Paolo,Umani-Ronchi, Achille
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p. 3357 - 3359
(2007/10/03)
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- Asymmetric allylation with chiral formamide catalysts
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The successful example of chiral formamides that function as asymmetric catalysts is described. (S,S)-N,N-Bis(α-methylbenzyl)formamide mediates the enantioselective addition of allyl- and crotyltrichlorosilanes to aliphatic aldehydes with the assistance of hexamethylphosphoramide (HMPA) to afford the corresponding homoallylic alcohols in up to 98% enantiomeric excess.
- Iseki, Katsuhiko,Mizuno, Shin,Kuroki, Yoshichika,Kobayashi, Yoshiro
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p. 977 - 988
(2007/10/03)
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- Application of 1,2:5,6-di-O-cyclohexylidene-D-mannitol as the chiral director in Matteson's asymmetric homologation
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1,2:5,6-Di-O-cyclohexylidene-D-mannitol is the good chiral director in Matteson's asymmetric homologation as indicated by the high enantiomeric excesses (ee's) of the secondary alcohols produced by treatment of the homologation products with alkyllithium
- Li, Guisheng,Kabalka, George W.
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- Enantioselective and Diastereoselective Additions of Allylic Stannanes to Aldehydes Promoted by a Chiral (Acyloxy)borane Catalyst
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A modified Yamamoto Lewis acid (CAB), prepared from the 2,6-dimethoxybenzoic ester of (R,R)- tartaric acid, and 1.5 equiv of BH3-THF was employed in additions of crotyltributyltin (6) and allyltributyltin (9) to representative achiral aldehydes in the presence of 2 equiv of (CF3CO)2O. The crotyltin additions proceeded with good to excellent diastereoselectivity and enantioselectivity affording the syn adducts 7a-e of 70-90% ee as major products (78:22-92:8). Addition of allylstannane 9 to cyclohexanecarboxaldehyde (1a) afforded the (R)-adduct of only 55% ee. In contrast, the use of Keek's BINOL catalyst gave 10, the allyl adduct of 1a, of 87% ee. However, addition of the crotylstannane to 1a with this catalyst led to a 65:35 mixture of syn and anti adducts 7a and 8a of 95% and 49% ee. Additions of crotylstannane 6 to (R)- and (S)-2-methyl-3-ODPS- propanal [(R)-11 and (S)-11] promoted by the modified CAB Lewis acid afforded the syn,syn and syn,anti products 12 and 14 in large predominance (98:2 and 90:10), indicative of effective complex control in the transition state. The results are consistent with the Corey H-bonded aldehyde transition-state proposal.
- Marshall, James A.,Palovich, Michael R.
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p. 4381 - 4384
(2007/10/03)
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- A chiral formamide: Design and application to catalytic asymmetric synthesis
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(S,S)-N,N-Bis(-α-methylbenzyl) formamide is the first example of chiral formamides that function as Lewis base catalysts to effectively serve catalytic asymmetric synthesis. The chiral formamide in combination with an additive, HMPA, catalyzes allylations
- Iseki, Katsuhiko,Mizuno, Shin,Kuroki, Yoshichika,Kobayashi, Yoshiro
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p. 2767 - 2770
(2007/10/03)
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