- Convenient Procedures for the Asymmetric Reduction of 1,4-Diphenylbutane-1, 4-dione and Synthesis of 2,5-Diphenylpyrrolidine Derivatives
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Asymmetric reduction of 1,4-diphenylbutane-1,4-dione (1) was carried out using the reducing agents NaBH4, BH3·THF, and PhNEt2·BH3 in combination with the chiral reagents (S)-(-)-α,α-diphenyl-2-pyrrolidinemethanol (4) or (S)-proline (5), in the presence of TMSCl or B(OMe)3 under various conditions to obtain the corresponding 1,4-diol 2 in 52% to 97% ee. The chiral 1,4-diol 2 was converted to various C2-symmetric (2S,5S)-2,5-diphenylpyrrolidine derivatives 3a-e (45 to 75% yield) via the corresponding dimesylate prepared using MsCl and Et3N.
- Periasamy, Mariappan,Seenivasaperumal, Muthu,Rao, Vutukuri Dharma
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- Transmetalation of organic groups from zirconacycles to haloboranes: A new route to borolane compounds
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The reaction of styrene and 'Cp2Zr' forms the trans-2,5-diphenylzirconacycle. Transmetalation of this zirconacyle with an equivalent of boron trichloride forms the 1-chloro-trans-2,5-diphenylborolane with retention of stereochemistry. This B-chloroborolane is converted into other boranes and can be oxidized to the diol.
- Cole, Thomas E.,Gonzalez, Tomas
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- Asymmetric hydrogenation of 1,4-diketones: facile synthesis of enantiopure 1,4-diarylbutane-1,4-diols
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Owing to the biological significance and great synthetic value of 1,4-diarylbutane-1,4-diols and their derivatives, increasingly considerable attention has been paid to developing effective synthetic methods for chiral 1,4-diarylbutane-1,4-diols. We herei
- Huang, Fanping,Shao, Pan-Lin,Song, Jingyuan,Wang, Jiang,Zhang, Xumu
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supporting information
p. 262 - 265
(2022/01/06)
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- Development of chiral bis-hydrazone ligands for the enantioselective cross-coupling reactions of aryldimethylsilanolates
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A palladium-catalyzed, enantioselective, aryl-aryl cross-coupling reaction using 1-naphthyldimethylsilanolates and chiral bis-hydrazone ligands has been developed. A family of glyoxal bis-hydrazone ligands containing various 2,5-diarylpyrrolidine groups was prepared to evaluate the influence of ligand structure on the rate and enantioselectivity of the cross-coupling. New synthetic routes to the 1-amino-2,5-diarylpyrrolidines were developed to enable the structure/reactivity-selectivity studies. Role reversal experiments of aryldimethylsilanolates and aryl bromides result in biaryl products with the same configuration and similar enantioselectivities implying that reductive elimination is the stereodetermining step. The origin of stereoselectivity is rationalized through computational modeling of diarylpalldium(II) complex which occurs through a conrotatory motion for the two aryl groups undergoing C-C bond formation.
- Denmark, Scott E.,Chang, Wen-Tau T.,Houk,Liu, Peng
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supporting information
p. 313 - 366
(2016/09/09)
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- Aerobic oxidative desymmetrization of meso-diols with bifunctional amidoiridium catalysts bearing chiral N-sulfonyldiamine ligands
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Asymmetric aerobic oxidation of a range of meso- and prochiral diols with chiral bifunctional Ir catalysts is described. A high level of chiral discrimination ability of Cpa? -Ir complexes derived from (S,S)-1,2-diphenylethylenediamine was successfully demonstrated by desymmetrization of secondary benzylic diols such as cis-indan-1,3-diol and cis-1,4-diphenylbutane-1,4-diol, providing the corresponding (R)-hydroxyl ketones with excellent chemo- and enantioselectivities. Enantiotopic group discrimination in oxidation of symmetrical primary 1,4- and 1,5-diols gave rise to chiral lactones with moderate ees under similar aerobic conditions.
- Moritani, Junki,Hasegawa, Yasuharu,Kayaki, Yoshihito,Ikariya, Takao
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supporting information
p. 1188 - 1191
(2014/02/14)
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- Efficient preparation of optically pure C2-symmetrical cyclic amines for chiral auxiliary
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Optically pure C2-symmetrical amines were efficiently synthesized from the corresponding diols obtained from the enantioselective borohydride reduction of the diketones catalyzed by the optically active β-ketoiminato cobalt(II) complex.
- Sato, Mitsuo,Gunji, Yasuhiko,Ikeno, Taketo,Yamada, Tohru
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p. 1434 - 1438
(2007/10/03)
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- Stereoselective Synthesis of anti-1,4-Diols by a BH3· THF-Mediated Rearrangement of 1,2-Disubstituted Cyclobutenes
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A new stereoselective rearrangement of cyclobutylboranes, obtained by the hydroboration of 1,2-disubstituted cyclobutenes, provides anti-1,4-diols with good-to-excellent diastereoselectivity. The mechanism of the rearrangement is discussed based on theoretical calculations.
- Knapp, Kolja M.,Goldfuss, Bernd,Knochel, Paul
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p. 5259 - 5265
(2007/10/03)
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- Facile reduction of aromatic aldehydes, ketones, diketones and oxo aldehydes to alcohols by an aqueous TiCl3/NH3 system: Selectivity and scope
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A simple and rapid procedure for the almost quantitative reduction of aromatic aldehydes, ketones, diketones and oxo aldehydes to alcohols by use of TiCl3/NH3 in aqueous methanol solution is reported. The reducing system distinguishes between different classes of aldehydes and/or ketones, and many functionalities that usually do not survive under reducing conditions are tolerated well. The concept of reversal of chemoselectivity has also been developed. A mechanism based on two sequential one-electron transfers from TiIII to the carbonyl carbon atom is proposed, the second SET becoming operative only in the presence of ammonium ion (either added or formed in situ). Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.
- Clerici, Angelo,Pastori, Nadia,Porta, Ombretta
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p. 3326 - 3335
(2007/10/03)
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- Stereoselective allylic C - H activation with tertiary alkylboranes: A new method for preparing cycloalkyl derivatives with three adjacent stereocenters
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A regio- and stereoselective migration takes place under mild conditions for tertiary organoboranes obtained by hydroboration of tetrasubstituted cyclic alkenes. A subsequent amination proceeds with perfect control of the stereo-chemistry. The scheme shows an example of this for the reaction of bicyclo[4.3.0]-non-1(6)-ene (1) to 2 via intermediates 3 and 4. Compound 2 is formed as the single diastereomer in 69% yield.
- Lhermitte, Frédéric,Knochel, Paul
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p. 2459 - 2461
(2007/10/03)
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- Oxazaborolidine-catalysed reduction of alk-2-ene-1,4-diones. A convenient access to chiral 1,4-diols
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An efficient method for the preparation of C2-symmetric, chiral alk-2- ene-1,4-diols (4) has been achieved, based on the borane-mediated reduction of symmetric alk-2-ene-1,4-diones (2) in the presence of oxazaborolidine (R)- 1. In general, the presence of the double bond in 2 has been beneficial (compared with the related saturated 1,4-diketones 3) not only as far as the stereoselectivity in the reduction step is concerned, but also because it allowed us to remove meso-4 by chomatography and/or to improve the stereochemical purity of several resulting mixtures of diols 4 by Sharpless' epoxidation. Enantioenricbed compounds 4 have been readily reduced to saturated diols with negligible loss of optical purity.
- Bach, Jordi,Berenguer, Ramon,Garcia, Jordi,Lopez, Marta,Manzanal, Judith,Vilarrasa, Jaume
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p. 14947 - 14962
(2007/10/03)
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- Asymmetric synthesis of trans-2,5-diphenylpyrrolidine: A C2-symmetric chiral amine
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(R,R)-2,5-Diphenylpyrrolidine of high enantiomeric purity (>98% e.e.) may be prepared from 1,4-diphenyl-1,4-butanedione in 4 steps and 64% overall yield. A key step is asymmetric reduction of the dione with Ipc2BCl.
- Chong,Clarke,Koch,Olbach,Taylor
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p. 409 - 418
(2007/10/02)
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- The Mechanism of Asymmetric Hydrogenation. Chiral Bis(diphenylphosphino)-α-phenylalkane Complexes in Catalytic and Structural Studies
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(R)-1,2-Bis(diphenylphosphino)phenylethane has been synthesised in good overall yield from (S)-mandelic acid ; its cationic rhodium(I) solvated complex has been shown to be effective in catalytic asymmetric hydrogenation with optical yields of up to 88percent having been observed.The n.m.r. spectra of complexes of this phosphine are discussed.Racemic (R*,R*)-1,3-bis(diphenylphosphino)-1,3-diphenylpropane and (R*,R*)-1,4-bis(diphenylphosphino)-1,4-diphenylbutane have been prepared.These form a range of rhodium complexes with dehydroamino-acids whose structures may be assigned on the basis of characteristic n.m.r.P-Rh and P-P coupling constants.
- Brown, John M.,Murrer, Barry A.
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p. 489 - 498
(2007/10/02)
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