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1.
Knapp S Yang C Pabbaraja S Rempel B Reid S Withers SG 《The Journal of organic chemistry》2005,70(19):7715-7720
[reaction: see text] An efficient 10-step preparation from 4-methoxypyridine of (2R,3R,4R)-2-acetamido-3,4-dihydroxypiperidine ("XylNAc-isofagomine") in optically active form is described. Key steps include an enantioselective reduction with catecholborane/(S)-2-methyl-CBS-oxazaborolidine, and a stereoselective pseudo-glycosylation of lithium azide by a cyclic sulfite ester. The title compound showed a Ki = 21 microM when evaluated against the N-acetyl-beta-hexosaminidase from Streptomyces plicatus. 相似文献
2.
《Tetrahedron: Asymmetry》1998,9(19):3365-3369
Some aromatic ketones have been reduced by borane or by catecholborane using oxazaborolidine as a catalyst. It has been found that, when borane is used, the enantiomeric excess of alcohol produced decreases as the substitution on the ortho position of benzene ring increases. However, for ketones with 2,6-disubstituted aryl substituents the enantiomeric excess increases when catecholborane is used. 相似文献
3.
4.
A convenient synthesis of immunosuppressive agent FTY720 (1) using the Petasis reaction was developed. 4-Octylbenzaldehyde (9) was converted into 1-ethenyl-4-octylbenzene (11) by two-step synthesis. Hydroboration of 11 using catecholborane and hydrolysis gave (E)-2-(4-octylphenyl)vinylboronic acid (4). The Petasis reaction of 4, dihydroxyacetone (3), and benzylamine following catalytic hydrogenation afforded FTY720 (1). 相似文献
5.
The first nickel complex bearing a boryl moiety, (PNP)Ni[B(catechol)](PNP = N[2-P(CHMe(2))(2)-4-methylphenyl](2)(-)), has been prepared, structurally characterized, and analyzed by DFT; this rare species is shown to be a recyclable reagent for the borylation of bromobenzene, via an unusual cycle, by applying the ingredients catecholborane and NaBH(4). 相似文献
6.
[formula: see text] The cross-coupling reaction of 2-(1-alkenyl)-1,3,2-benzodioxaboroles, obtained from alkynes and catecholborane, and other boron derivatives with a lactam-derived N-Boc enol triflate occurred under very mild conditions in a THF-water medium employing (Ph3P)2PdCl2 as a catalyst, providing the corresponding 6-substituted N-Boc 3,4-dihydro-2H-pyridines in high yields. 相似文献
7.
[reaction: see text] Reaction of enyne 1 with catecholborane catalyzed by a 1:1 mixture of [Rh(COD)(2)](+)SbF(6)(-) and (S)-BINAP (5 mol %) followed by Pd-catalyzed arylation with p-IC(6)H(4)CF(3) gave benzylidenecyclopentane 5 in 65% yield with 88% ee. Rhodium-catalyzed asymmetric cyclization/hydroboration followed either by Pd-catalyzed arylation or by oxidation was applied to the synthesis of a number of chiral, nonracemic carbocycles and heterocycles. 相似文献
8.
A general method is described for asymmetric synthesis of both syn- and anti-1,3-amino alcohols. The first application of metalloenamines derived from N-sulfinyl imines is reported for the highly diastereoselective addition to aldehydes. The reduction of the product beta-hydroxy N-sulfinyl imines 2 with catecholborane and LiBHEt(3) provides syn- and anti-1,3-amino alcohols with very high diastereomeric ratios. This method was found to be effective for a variety of substrates incorporating either aromatic or various aliphatic substituents. The convergent and efficient asymmetric syntheses of the two natural products, (-)-8-epihalosaline and (-)-halosaline, were also accomplished. 相似文献
9.
Intramolecular Cyclopropanation of 1,4‐Dienes through Hydroboration–Homologation: Easy Access to Bicyclo[3.1.0]hexanes 下载免费PDF全文
Dr. Gong Xu Prof. Philippe Renaud 《Angewandte Chemie (International ed. in English)》2016,55(11):3657-3661
An intramolecular cyclopropanation reaction involving B‐(1‐chloroalkyl)catecholborane intermediates generated from 1,4‐dienes through hydroboration with catecholborane and Matteson homologation was developed. This sequential procedure leading to bicyclo[3.1.0]hexanes involves the formation of three new sigma C?C bonds at the same carbon atom. A mechanistic study supports the involvement of carbocationic intermediates. 相似文献
10.
Segarra AM Daura-Oller E Claver C Poblet JM Bo C Fernández E 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(24):6456-6467
This study attempts to rationalise the unpredictable performance of transition metal catalysed asymmetric hydroboration of vinylarenes on varying the precursor of the catalyst from cationic to neutral species, [M(cod)(L-L)]BF4, [M(mu-Cl)(cod)]2/(L-L), the metal (M=Rh and Ir), and the hydroborating reagent (catecholborane, pinacolborane). The approaches are based on the agreement between experimental data provided by (R)-Binap and (R)-Quinap modified catalytic systems and computational data evidenced by DFT calculations and QM/MM strategies. Unprecedentedly high enantiomeric excesses in the hydroboration/oxidation of vinylarenes with both electron-withdrawing substituents ((R)-(+)-1-p-F-phenylethanol, ee up to 92 %) and electron-releasing substituents ((R)-(+)-1-p-MeO-phenylethanol, ee up to 98 %), can be attributed to a rhodium halide key intermediate. 相似文献
11.
Andrei Korostylev Ilya Gridnev John M. Brown 《Journal of organometallic chemistry》2003,680(1-2):329-334
A novel triarylphosphite ligand has been prepared directly from both enantiomers of BINOL and a single enantiomer of 1′-(isoquinolyl)-2-naphthol. In one of the two cases cationic Rh complex proved to be reasonably effective in the asymmetric hydroboration of electron-poor styrenes. It was possible to identify binuclear reactive intermediates when the hydroboration pre-catalyst was examined in the presence of catecholborane at low temperatures. 相似文献
12.
Kato Y Niiyama K Jona H Okada S Akao A Hiraga S Tsuchiya Y Tomimoto K Mase T 《Chemical & pharmaceutical bulletin》2002,50(8):1066-1072
An asymmetric synthesis of a selective endothelin A receptor antagonist 1b is described. Asymmetric conjugate addition of aryllithium derived from 18 to the chiral oxazoline 17 followed by hydrolysis afforded 15 in 96% ee via purification as (S)-(-)-1-phenylethylamine salt. Pd(OAc)(2)/dppf (1,1'-bis(diphenylphosphino)ferrocene) catalyzed carbonylation followed by chemoselective addition of aryllithium derived from 23 which gave ketone 24. Diastereoselective reduction of the ketone with catecholborane followed by concomitant activation of the resulting alcohol and cyclization gave the late intermediate 26. Introduction of amino moiety on the pyridine ring by imidoyl rearrangement followed by deprotection and purification by crystallization furnished the enantiomerically pure target molecule 1b in 8% overall yield from 16. 相似文献
13.
Dr. Franck Ulm Dr. Yann Cornaton Dr. Jean-Pierre Djukic Prof. Michael J. Chetcuti Prof. Vincent Ritleng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(41):8916-8925
The pentamethylcyclopentadienyl N-heterocyclic carbene nickel complex [Ni(η5-C5Me5)Cl(IMes)] (IMes=1,3-dimesitylimidazol-2-ylidene) efficiently catalyses the anti-Markovnikov hydroboration of alkenes with catecholborane in the presence of a catalytic amount of potassium tert-butoxide, and joins the very exclusive club of nickel catalysts for this important transformation. Interestingly, the regioselectivity can be reversed in some cases by using pinacolborane instead of catecholborane. Mechanistic investigations involving control experiments, 1H and 11B NMR spectroscopy, cyclic voltammetry, piezometric measurements and DFT calculations suggest an initial reduction of the NiII precursor to a NiI active species with the concomitant release of H2. The crucial role of the alkoxo-catecholato-borohydride species resulting from the reaction of potassium tert-butoxide with catecholborane in the formation of an intermediate nickel-hydride species that would then be reduced to the NiI active species, is highlighted. 相似文献
14.
The hydroboration of terminal alkylselenoacetylenes 1 in the presence of 3 mol% of Pd (PPh3)4 with catecholborane 2 followed by hydrolysis, undergo a rapid reaction with iodine under the influence of sodium hydroxide at-10°C in THF to afford a novel method for the regio-and stereospecific synthesis of (E)-2-alkylseleno-1-vinyl iodides 4. 相似文献
15.
[reaction: see text] Two simple TADDOL-derived monodentate ligands, the (1R,2S)-2-phenylcyclohexanol-derived phosphite and the N,N-(phenylbenzyl)phosphoramidite, give comparably high levels of enantioselectivity (90-96% ee) in the rhodium-catalyzed hydroborations of substituted styrenes bearing either electron-donating or electron-withdrawing substituents. Rhodium(I) chloride and tetrafluoroborate catalyst precursors give comparable results. Pinacolborane is superior to catecholborane in these reactions. 相似文献
16.
Kapat A König A Montermini F Renaud P 《Journal of the American Chemical Society》2011,133(35):13890-13893
A one-pot procedure for the efficient hydroazidation of alkenes involving hydroboration with catecholborane followed by reaction with benzenesulfonyl azide in the presence of a radical initiator is described. The regioselectivity is controlled by the hydroboration step and corresponds in most cases to an anti-Markovnikov regioselectivity. This procedure is applicable to a wide range of alkenes and gives excellent results with 1,2-disubstituted and trisubstituted alkenes. 相似文献
17.
the chemoselective conversion of allyl and prop-2-ynyl acetals as well as ketals by reductive cleavage with catecholborane into the corresponding allyl and prop-2-ynyl ethers is described. 相似文献
18.
Blake AJ Cunningham A Ford A Teat SJ Woodward S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(19):3586-3594
LiGaH4, in combination with the S,O-chelate 2-hydroxy-2'-mercapto-1,1'-binaphthyl (MTBH2), forms an active catalyst for the asymmetric reduction of prochiral ketones, with catecholborane as the hydride source. Enantioface differentiation is on the basis of the steric requirements of the ketone substituents. Aryl/ n-alkyl ketones are reduced in 90-93% ee and RC(O)Me (e.g. R = iPr, cycloC6H11, tBu) in 60-72% ee. Other borane sources and alternative catalyst structures based on indium do not form enantioselective catalysts. 相似文献
19.
The scope of substrate-controlled diastereoselective hydroborations can be considerably enhanced by a boron-zinc exchange reaction, providing organozinc derivatives that react with a broad range of electrophiles. Even normally unreactive boronic esters, obtained by Rh-catalyzed hydroboration with catecholborane, react readily with iPr2Zn providing the corresponding zinc reagents in high diastereoselectivity. 相似文献
20.
Exposure of monoenone monoketones to catecholborane in THF at ambient temperature results in tandem 1,4-reduction-aldol cyclization. For aromatic and heteroaromatic enones, six-membered cyclic aldol products are formed in excellent yield with high levels of syn diastereoselectivity. Five-membered ring formation proceeds less readily, but the yield of cyclized product is improved through introduction of Rh(I) salts. 相似文献