72029-73-3Relevant academic research and scientific papers
Enders SAMP-hydrazone as traceless auxiliary in the asymmetric 1,4-addition of cuprates to enones
Sammet, Karsten,Gastl, Christoph,Baro, Angelika,Laschat, Sabine,Fischer, Peter,Fettig, Ina
supporting information; experimental part, p. 2281 - 2290 (2010/12/29)
Conjugate additions of Gilman cyanocuprates to (5)-N-amino-2- (methoxymethyl)pyrrolidine (SAMP)-hydrazones 4, 5 derived from cyclic and acyclic α,β-unsaturated ketones were investigated. A protocol utilizing copper(II) sulfate/ammonium chloride was evolved, which allowed cleavage of SAMP (S)-1 under the hydrolysis and work-up conditions, followed by recovery of the auxiliary with ethylenediaminetetraacetic acid (EDTA). The enantioselectivity of cuprate additions was dominated for cyclic SAMP-hydrazones 4 by the cuprate alkyl substituent and the ring size, in the case of acyclic arylidene SAMP-hydrazones 5, however, by the nature of the aryl substituent. Electron-donating substituents gave poor enantiomeric excesses, whereas electron-withdrawing groups provided excellent ee values of 98-99%. The configuration of the new stereocenter was determined to be (R). Moreover, a reaction sequence was developed which integrates a tandem 1,4-addition/ methylation and traceless hydrolytic cleavage of the auxiliary (S)-1 in a one-pot reaction, resulting in enantiomerically pure methyl ketones 11-13, each of them with > 99% ee.
METHODS FOR PREPARING DIORGANOZINC COMPOUNDS
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Page/Page column 19-20, (2009/01/20)
There are provided methods for preparing the diorganozmc compounds of formula R2Zn (I or Ia), where R is a defined organic radical, and the two R groups can be the same or different The starting material is the zinc compound ZnX2 (II) or R2ZnX (IIa), where X is a defined anion and R2 is a defined organic radical. The zinc reagent of type II is combined with a Grignard reagent and also, when X is Cl or Br, with an alkali metal reagent (VI) to form the diorganozinc product (I or Ia). Also provided are methods for preparing the zinc alcoholates of formula Zn(OR1)2 by reaction of ZnX2, where X = Cl or Br, with an alkali metal reagent of the formula MOR1, where M = Na or K, and where R1 is a defined organic radical.
Hydride reduction of alpha, beta-unsaturated carbonyl compounds using chiral organic catalysts
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Page/Page column 27, (2008/06/13)
Nonmetallic, chiral organic catalysts are used to catalyze the 1,4-hydride reduction of an α,β-unsaturated carbonyl compound. The α,β-unsaturated carbonyl compound may be an aldehyde or cyclic ketone, and the hydride donor may be a dihydropyridine. The reaction is enantioselective, and proceeds with a variety of hydride donors, catalysts, and substrates. The invention also provides compositions effective in carrying out the 1,4-hydride addition of α,β-unsaturated carbonyl compounds.
Conjugate Additions of Organocuprates to Cycloalkenone Complexes of the Chiral Rhenium Lewis Acid 5-C5H5)Re(NO)(PPh3)>(+). Enantioselective Syntheses of 3-Substituted Cycloalkanones
Wang, Yan,Gladysz, J. A.
, p. 903 - 909 (2007/10/02)
Reactions of organocuprates R2CuLi and cycloalkenone complexes (+)-(R)-(+)BF4(-) (n = 2, 1) are conducted in THF or CH2Cl2 between -15 deg C and -116 deg C.Workups with aqueous HI give the corresponding 3-substituted cycloalkanones and iodide complex (η5-C5H5)Re(NO)(PPh3) (I).Under optimized conditions, 3-substituted cyclohexanones are obtained in 39-83percent yields and 64-86percent ee (R = Me, R; n-Bu, R; t-Bu, S; Ph, S or R), and 3-substituted cyclopentanones are obtained in 50-73percent yields and 79-93percent ee (R = Me, R; Ph, S).Evidence for intermediate enolate complexes is presented, protocols for recycling the chiral rhenium auxiliary are described, and possible mechanisms of 1,4-asymmetric induction are discussed.
SYNTHESIS OF (+)-α-CURCUMENE, (+)-CURCUMONE AND (-)-METHYL CITRONELLATE STARTING FROM OPTICALLY PURE 5-TRIMETHYLSILYL-2-CYCLOHEXENONE
Asaoka, Morio,Shima, Kunuhisa,Fujii, Naoaki,Takei, Hisashi
, p. 4757 - 4766 (2007/10/02)
1,4-addition of Grignard reagents in the presence of chlorotrimethylsilane to 5-trimethylsilyl-2-cyclohexanone (1) proceeded in a highly diastereoselective manner to give trans adducts in high yields. (+)-α-Curcumene, (+)-curcumone and (-)-methyl citronellate were synthesized starting from optically pure 1.
Synthesis of Chiral 5-Substituted Cyclohex-2-enones from 5-Trimethylsilylcyclohex-2-enone
Asaoka, Morio,Shima, Kunihisa,Takei, Hisashi
, p. 430 - 431 (2007/10/02)
Optically active and racemic-5-substituted cyclohex-2-enones were synthesized from 5-trimethylsilylcyclohex-2-enone.
ENZYMATIC "IN VITRO" REDUCTION OF KETONES. VI.(1) Reduction rates and stereochemistry of the HLAD-catalyzed reduction of 3-alkyl- and 4-alkylcyclohexanones.
Osselaer, T. A. Van,Lemiere, G. L.,Lepoivre, J. A.,Alderweireldt, F. C.
, p. 133 - 150 (2007/10/02)
Reaction rate constants for the catalytic step HLAD-NADH + ketone * HLAD-NAD+ + alcohol in the HLAD-catalyzed reduction of 3-alkyl- and 4-alkylcyclohexanones are determined from initial rate measurements in the coenzyme recycling system ketone-ethanol-NAD+-HLAD.By rate measurements at several temperatures, activation parameters were determined and isokinetic relationships tracked down.Two different isokinetic relationships show that the 3-alkylcyclohexanones pass through an other type of transition state than cyclohexanone and the 4-alkylcyclohexanones, which means that they have a different arrangement on the HLAD-NADH complex.The results are rationalized in view of the most recent principles on nucleophilic additions to carbonyl functions.The resulting model for the HLAD-catalyzed reduction adequately explains the observed rate accelerating and decelerating effects and the stereochemistry of the reduction as well.
