- Auxiliary-Directed Diastereoselectivity in the Claisen Rearrangement of Glycolate Esters
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Examples are presented in which the stereochemical course of the Claisen rearrangement of allylic glycolates is controlled by a chiral substituent appended to the glycolate hydroxyl.
- Kallmerten, James,Gould, Thomas J.
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- Catalytic asymmetric synthesis of esters from ketenes
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By building on elementary principles of Bronsted acid-base chemistry, a nucleophile-catalyzed method for the asymmetric synthesis of esters from ketenes has been transformed into a much more versatile and effective Bronsted acid-catalyzed process. The product aryl esters can be converted into useful derivatives, such as enantioenriched alcohols and carboxylic acids. Copyright
- Wiskur, Sheryl L.,Fu, Gregory C.
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Read Online
- Identification of an Esterase Isolated Using Metagenomic Technology which Displays an Unusual Substrate Scope and its Characterisation as an Enantioselective Biocatalyst
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Evaluation of an esterase annotated as 26D isolated from a marine metagenomic library is described. Esterase 26D was found to have a unique substrate scope, including synthetic transformations which could not be readily effected in a synthetically useful manner using commercially available enzymes. Esterase 26D was more selective towards substrates which had larger, more sterically demanding substituents (i. e. iso-propyl or tert-butyl groups) on the β-carbon, which is in contrast to previously tested commercially available enzymes which displayed a preference for substrates with sterically less demanding substituents (e.g. methyl group) at the β-carbon. (Figure presented.).
- Gavin, Declan P.,Murphy, Edel J.,Foley, Aoife M.,Castilla, Ignacio Abreu,Reen, F. Jerry,Woods, David F.,Collins, Stuart G.,O'Gara, Fergal,Maguire, Anita R.
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p. 2466 - 2474
(2019/03/11)
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- Rh-Catalyzed Asymmetric Hydrogenation of β-Branched Enol Esters for the Synthesis of β-Chiral Primary Alcohols
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An asymmetric hydrogenation of β-branched enol esters has been developed for the first time, providing a new route for the synthesis of β-chiral primary alcohols. Using a (S)-SKP-Rh complex bearing a large bite angle and enol ester substrates possessing an O-fomyl directing group, the desired products were obtained in quantitative yields and with excellent enantioselectivities.
- Liu, Chong,Yuan, Jing,Zhang, Jian,Wang, Zhihui,Zhang, Zhenfeng,Zhang, Wanbin
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p. 108 - 111
(2018/01/17)
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- Impact of variation of the acyl group on the efficiency and selectivity of the lipase-mediated resolution of 2-phenylalkanols
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By tuning the steric properties of the acyl group to control the efficiency and selectivity of the resolution, 2-phenyl-1-propanol 1a was prepared by lipase-catalysed hydrolysis using a short-chain acyl group, with E-values of up to 66 (ee up to 95%). 2-Phenylbutan-1-ol 1b was similarly resolved (up to 86% ee) using the optimised conditions, while the ester of the more sterically demanding 3-methyl-2-phenylbutan-1-ol 1c proved resistant to enzymatic hydrolysis under these conditions.
- Foley, Aoife M.,Gavin, Declan P.,Joniec, Ilona,Maguire, Anita R.
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p. 1144 - 1153
(2017/09/15)
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- Synthesis and Antibacterial Activity of Four Stereoisomers of the Spider-Pathogenic Fungus Metabolite Torrubiellone D
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Four stereoisomers of the spider-pathogenic fungus metabolite torrubiellone D were synthesized for the first time in 10% overall yield starting from l-tyrosine or d-tyrosine. The 3-decatrienoyl side chain was assembled and attached via (E)-selective HWE and Wittig olefinations. Their antibiotic activities against drug-susceptible Escherichia coli strains differed considerably.
- Bruckner, Sebastian,Bilitewski, Ursula,Schobert, Rainer
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supporting information
p. 1136 - 1139
(2016/03/15)
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- Catalytic enantioselective ethylalumination of terminal alkenes: Substrate effects and absolute configuration assignment
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The chemo- and enantioselectivity of the reaction of alkenes with AlEt3 catalyzed by bis(1-neomenthylindenyl)zirconium dichloride has been studied. The reaction with linear alkenes in a chlorinated solvent (CH2Cl2) gives m
- Parfenova, Lyudmila V.,Kovyazin, Pavel V.,Tyumkina, Tatyana V.,Makrushina, Alyona V.,Khalilov, Leonard M.,Dzhemilev, Usein M.
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p. 124 - 135
(2015/02/19)
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- Filling the gaps in the challenging asymmetric hydroboration of 1,1-disubstituted alkenes with simple phosphite-based phosphinooxazoline iridium catalysts
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We have identified a readily accessible phosphinooxazoline-based phosphite-oxazoline catalytic system, (S)-4-isopropyl-2-{2-[(3,3′,5,5′-tetra-tert-butyl-1,1′-biphenyl-2,2′-diyl)phosphite]-phenyl}-2-oxazoline (L1a), that can hydroborate a range of 1,1-disubstituted aryl olefins with high enantioselectivity (up to 94%), excellent yields and perfect regioselectivity. The new phosphite-oxazoline ligands efficiently hydroborate a broader range of olefins than previous phosphinooxazoline ligands. In particular, a wide range of α-tert-butylstyrenes can be hydroborated that bear aryl substituents with different electronic and steric properties, which complements previous results with N-heterocyclic copper catalysts, the only other system reported to date that has achieved these reactions.
- Magre, Marc,Biosca, Maria,Pmies, Oscar,Diguez, Montserrat
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p. 114 - 120
(2015/01/30)
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- A new mechanism of enantioselectivity toward chiral primary alcohol by lipase from Pseudomonas cepacia
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The stereo-recognition of chiral primary alcohols by lipase from Pseudomonas cepacia was found to deviate from earlier observations. Enantioselectivity toward 14 pairs of chiral primary alcohol esters by this lipase was dependent on the existence of an Onon-α(oxygen at non-α-position of the acyloxy group) in the alcohol moiety, and decreased as the size of the acyl moiety increased. Chemical modification on the lipase and molecular dynamics simulations indicated that Tyr29located within the catalytic cavity forms a hydrogen bond with the Onon-αof the preferred enantiomer of the primary alcohol ester. However, a larger acyl moiety suffered stronger hindrance from the catalytic cavity wall of the lipase, pushing the Onon-αaway from Tyr29, and thus weakening the stereo-recognition.
- Meng, Xiao,Guo, Li,Xu, Gang,Wu, Jian-Ping,Yang, Li-Rong
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p. 109 - 115
(2014/12/11)
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- Asymmetric rearrangement of racemic epoxides catalyzed by chiral Br?nsted acids
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This paper describes a chiral Br?nsted acid catalyzed asymmetric 1,2-rearrangement of racemic epoxides via a hydrogen-shift process for the synthesis of chiral aldehydes, and, followed by a reduction, a variety of optically active alcohols can be furnished in moderate yields with up to 50% ee. Especially, a facile one-pot synthesis of chiral alcohols directly from simple alkenes by a sequential epoxidation, rearrangement, and reduction has also been realized.
- Zhuang, Minyang,Du, Haifeng
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supporting information
p. 1460 - 1462
(2013/05/08)
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- Catalytic asymmetric intermolecular C-H insertion of 1,4-cyclohexadiene with α-alkyl-α-diazoesters using chiral dirhodium(II) carboxylates
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The first example of dirhodium(II) complex-catalyzed asymmetric intermolecular C-H insertion with α-alkyl-α-diazoesters is described. The reaction of 1,4-cyclohexadiene with 2,4-dimethyl-3-pentyl α-alkyl-α-diazoacetates under catalysis by dirhodium(II) te
- Goto, Takayuki,Onozuka, Tomohiro,Kosaka, Yuhei,Anada, Masahiro,Takeda, Koji,Hashimoto, Shunichi
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p. 1647 - 1659
(2013/08/23)
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- METHODS OF MODULATING THE ACTIVITY OF THE MC1 RECEPTOR AND TREATMENT OF CONDITIONS RELATED TO THIS RECEPTOR
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The present invention provides compounds of Formula (I) that are useful for binding and/or modulating the biological activity of the melanocortin-1 receptor (MC1R). Compounds of this invention can be used to treat diseases and/or conditions in which modulation of MC1R is beneficial. Such diseases and/or conditions include, but are not limited to, hyperpigmentation (including melasma), hypopigmentation (including vitiligo), melanoma, basal cell carcinoma, squamous cell carcinoma, erythropoietic protoporphyria, polymorphous light eruption, solar urticaria, photosensitivity, sunburn, inflammatory diseases, aberrant fibroblast activity and pain.
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Page/Page column 57; 58
(2012/06/16)
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- Highly regio- and enantioselective catalytic asymmetric hydroboration of α-substituted styrenyl derivatives
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The catalytic asymmetric hydroboration of a variety of 1,1-disubstituted olefins has been achieved with excellent yields, perfect regioselectivity and in some cases, high levels of enantioselectivity using readily accessible iridium catalyst.
- Mazet, Clement,Gerard, David
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supporting information; experimental part
p. 298 - 300
(2011/02/24)
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- METHODS OF MODULATING THE ACTIVITY OF THE MC1 RECEPTOR AND TREATMENT OF CONDITIONS RELATED TO THIS RECEPTOR
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The present invention provides compounds of Formula (I) that are useful for binding and/or modulating the biological activity of the melanocortin-1 receptor (MC1R). Compounds of this invention can be used to treat diseases and/or conditions in which modulation of MC1R is beneficial. Such diseases and/or conditions include, but are not limited to, hyperpigmentation (including melasma), hypopigmentation (including vitiligo), melanoma, basal cell carcinoma, squamous cell carcinoma, erythropoietic protoporphyria, polymorphous light eruption, solar urticaria, photosensitivity, sunburn, inflammatory diseases, aberrant fibroblast activity and pain.
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Page/Page column 104-105
(2010/09/17)
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- METHODS OF MODULATING THE ACTIVITY OF THE MC3 AND/OR MC4 RECEPTORS AND TREATMENT OF CONDITIONS RELATED TO THESE RECEPTORS
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The present invention provides compounds of Formula (I) that are useful for modulating the biological activity of the melanocortin-3 receptor (MC3R) and / or the melanocortin-4 receptor (MC4R). Compounds of this invention can be used to treat diseases and/or conditions in which modulation of MC3R and / or MC4R is beneficial. Such diseases and/or conditions include, but are not limited to, obesity, eating disorders (such as cachexia, anorexia, weight gain, weight loss), metabolic syndrome, diabetes, sexual dysfunction (such as erectile dysfunction and female sexual dysfunction), anxiety, depression, inflammation, addiction and alcohol intake.
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Page/Page column 120
(2010/09/17)
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- N-heterocyclic carbene-mediated enantioselective addition of phenols to unsymmetrical alkylarylketenes
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Chiral N-heterocyclic carbenes (NHCs) mediate the enantioselective addition of 2-phenylphenol to unsymmetrical alkylarylketenes, delivering α-alkyl-α-arylacetic acid derivatives with good levels of enantiocontrol (up to 84% ee). Enantiodivergent stereochemical outcomes are observed using 2-phe-nylphenol and benzhydrol in the NHC-promoted esterification reaction using a triazolium precatalyst derived from pyroglutamic acid, consistent with distinct mechanistic pathways operating within these processes.
- Concellon, Carmen,Duguet, Nicolas,Smith, Andrew D.
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supporting information; experimental part
p. 3001 - 3009
(2010/03/26)
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- 3-AMINOALKYL-1,4-DIAZEPAN-2-ONE MELANOCORTIN-5 RECEPTOR ANTAGONISTS
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The present invention provides compounds of Formula (I) that are useful for modulating the biological activity of the melanocortin-5 receptor (MC5R). Compounds of this invention can be used to treat diseases and/or conditions in which downregulation of MC5R is beneficial. Such diseases and/or conditions include, but are not limited to, acne, seborrhea, seborrheic dermatitis, cancer, and inflammatory diseases.
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Page/Page column 123
(2009/09/08)
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- Copper-catalyzed asymmetric allylic substitution with aryl and ethyl Grignard reagents
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Phenyl- and ethyl-magnesium bromides undergo regioselective asymmetric allylic substitution with high enantioselectivity under the catalysis of chiral amidophosphane-copper(i) complexes. The Royal Society of Chemistry.
- Selim, Khalid B.,Yamada, Ken-Ichi,Tomioka, Kiyoshi
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supporting information; experimental part
p. 5140 - 5142
(2009/03/11)
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- Catalytic asymmetric hiyama cross-couplings of racemic α-bromo esters
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The first catalytic asymmetric cross-coupling of α-halo carbonyl compounds with aryl metal reagents has been developed, thereby generating synthetically useful α-aryl carboxylic acid derivatives in good enantiomeric excess. The method can also be applied to enantioselective alkenylation reactions. Copyright
- Dai, Xing,Strotman, Neil A.,Fu, Gregory C.
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p. 3302 - 3303
(2008/10/09)
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- Ru-catalyzed asymmetric hydrogenation of racemic aldehydes via dynamic kinetic resolution: Efficient synthesis of optically active primary alcohols
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A highly efficient asymmetric hydrogenation of racemic α-arylaldehydes via dynamic kinetic resolution has been developed by using [RuCl2(SDPs)(diamine)] complexes as catalysts, providing chiral primary alcohols in excellent enantioselectivities. Copyright
- Xie, Jian-Hua,Zhou, Zhang-Tao,Kong, Wei-Ling,Zhou, Qi-Lin
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p. 1868 - 1869
(2007/10/03)
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- Catalytic asymmetric hydrogenation of aldehydes
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Racemic α-arylaldehydes provide the corresponding primary alcohols via dynamic kinetic resolution in excellent enantioselectivities and yields upon hydrogenation using a Noyori ruthenium catalyst; for example, the biologically active (S)-enantiomer of the non-steroidal anti-inflammatory drug ibuprofen could be synthesized via catalytic enantioselective hydrogenation of aldehyde 1f followed by oxidation with potassium permanganate in 76% isolated yield and 96: 4 er. The Royal Society of Chemistry.
- Li, Xiaoguang,List, Benjamin
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p. 1739 - 1741
(2008/02/03)
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- Catalytic asymmetric couplings of ketenes with aldehydes to generate enol esters
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(Chemical Equation Presented) With a little help from the ferrocenyl catalyst ((-)-1), a wide array of α-arylalkanoic acid derivatives can be produced from the catalytic asymmetric coupling of ketenes with aldehydes (see scheme). The enol esters are readily transformed into other useful families of compounds such as carboxylic acids and alcohols.
- Schaefer, Carsten,Fu, Gregory C.
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p. 4606 - 4608
(2007/10/03)
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- 4-((PHENOXYALKYL)THIO)-PHENOXYACETIC ACIDS AND ANALOGS
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The invention features 4-((phenoxyalkyl)thio)-phenoxyacetic acids and analogs, compositions containing them, and methods of using them as PPAR delta modulators to treat or inhibit the progression of, for example, dyslipidemia.
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(2010/02/11)
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- Stereoselective Construction of Acyclic Carbon Chains by a One-Pot Coupling Process Based on Alkenyloxazoline-Titanium Complexes
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A versatile organometallic intermediate, an alkenyloxazoline-titanium complex, has been developed that enables one-pot multicomponent diastereoselective and asymmetric coupling processes to be achieved in a remarkably efficient manner (see scheme).
- Mitsui, Kazuhisa,Sato, Takayuki,Urabe, Hirokazu,Sato, Fumie
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p. 490 - 492
(2007/10/03)
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- Stereoselective pinacol-type rearrangement of 2,3-epoxy alcohols with retention of configuration mediated by bis(iodozincio)methane
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Retention of the configuration is observed in the pinacol-type rearrangement of 2,3-epoxy alcohols 1 in the presence of bis(iodozincio)methane (2). The 1,3-migration of the hydroxymethyl group affords an intermediate 2-hydroxyaldehyde, which is methylenat
- Matsubara, Seijiro,Yamamoto, Hiromasa,Oshima, Koichiro
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p. 2837 - 2840
(2007/10/03)
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- 1,2-Asymmetric induction in the radical addition of organotin hydrides to (-)-menthyl(E)-2,3-disubstituted propenoates
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The results obtained in the free radical hydrostannation of (-)-menthyl(E)-2,3-diphenylpropenoate (1) with tri-n-butyl- and triphenyltin hydride, and of (-)-menthyl(E)-2-phenyl-2-butenoate (7) with trimethyltin hydride are reported. The absolute configuration of the new organotin adducts was determined by combining 1H- and 13C-NMR data with chemical correlation. The additions took place in all cases following a syn stereochemistry that led to diastereomeric excesses ranging between 73 and 100%. The observed stereochemistry is explained, taking into account both the allylic strain and the hyperconjugation with β-trialkyltin substituent existing in the intermediate radicals. Full 1H-, 13C- and 19Sn-NMR data are given.
- Mandolesi,Koll,Chopa,Podesta
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p. 151 - 159
(2007/10/03)
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- Stereospecific rearrangements of optically active 2-aryl-3-ethenyloxiranes to give optically active β-ethenylbenzeneethanols: Benzyl vs. allyl cations and an efficient synthesis of (s)-ibuprofen
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Rearrangements of aryl- and ethenyl-substituted oxiranes proceed well in the presence of triethylsilane and BF3 to give optically active alcohols, which we have used for a synthesis of (S)-ibuprofen 1. We have also shown that a vinyl group migrates to a benzylic cation faster than a phenyl group migrates to an allyl cation.
- Jung, Michael E.,Anderson, Karen L.
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p. 2605 - 2608
(2007/10/03)
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- Pseudoephedrine as a practical chiral auxiliary for the synthesis of highly enantiomerically enriched carboxylic acids, alcohols, aldehydes, and ketones
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The use of pseudoephedrine as a practical chiral auxiliary for asymmetric synthesis is described in full. Both enantiomers of pseudoephedrine are inexpensive commodity chemicals and can be N-acylated in high yields to form tertiary amides. In the presence of lithium chloride, the enolates of the corresponding pseudoephedrine amides undergo highly diastereoselective alkylations with a wide range of alkyl halides to afford α-substituted products in high yields. These products can then be transformed in a single operation into highly enantiomerically enriched carboxylic acids, alcohols, aldehydes, and ketones.
- Myers, Andrew G.,Yang, Bryant H.,Chen, Hou,McKinstry, Lydia,Kopecky, David J.,Gleason, James L.
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p. 6496 - 6511
(2007/10/03)
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- Synthesis of compounds with predetermined chirality
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A method for synthesizing enantiomerically enriched chemical intermediates with predetermined chirality is described. The method comprises formation of a pseudoephedrine amide, followed by stereoselective alkylation at the alpha carbon. The chiral auxiliary can then be cleaved off, affording chiral end products useful for further transformations. The enantiomeric enrichment of the chiral end products may exceed 98%, and the chiral auxiliary can be recovered. Novel amides of pseudoephedrine used in this method are also disclosed.
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- Enantioselective acylation of primary and secondary alcohols catalyzed by lipase QL from Alcaligenes sp.: A predictive active site model for lipase QL to identify which enantiomer of an alcohol reacts faster in this acylation
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Lipase QL (from Alcaligenes sp.)-catalyzed acylation of alcohols using isopropenyl acetate as the acylating agent in diisopropyl ether converted preferentially primary alcohols with an S configuration and secondary alcohols with an R configuration into the corresponding homochiral acetates. On the basis of observed enantiomer selectivities, a predictive active site model for lipase QL is proposed for identifying which enantiomer of a primary or a secondary alcohol reacts faster in this acylation. Copyright (C) 1996 Published by Elsevier Science Ltd.
- Naemura, Koichiro,Murata, Masaki,Tanaka, Rie,Yano, Masashi,Hirose, Keiji,Tobe, Yoshito
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p. 3285 - 3294
(2007/10/03)
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- Lithium amidotrihydroborate, a powerful new reductant. Transformation of tertiary amides to primary alcohols
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Lithium amidotrihydroborate (LiH2NBH3, LAB) is a new and highly nucleophilic reducing agent that is easily prepared by deprotonation of the commercial reagent borane-ammonia complex (H2NBH3) with n-BuLi in tetrahydrofuran (THF) at 0°C. LAB is found to be a superior reagent for the transformation of tertiary amides into the corresponding primary alcohols.
- Myers, Andrew G.,Yang, Bryant H.,Kopecky, David J.
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p. 3623 - 3626
(2007/10/03)
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- Lipase YS-catalysed Acylation of Alcohols: a Predictive Active Site Model for Lipase YS to Identify which Enantiomer of a Primary or a Secondary Alcohol Reacts Faster in this Acylation
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Primary alcohols having a hydroxymethyl group at an S chiral centre and secondary alcohols with an R configuration are preferentially acylated to give the corresponding acetates by lipase YS-catalysed acylation in diisopropyl ether; a predictive cubic-spaced active site model for lipase YS is proposed for identifying which enantiomer of a primary or a secondary alcohol reacts faster in this acylation.
- Naemura, Koichiro,Fukuda, Ritsuko,Konishi, Masayoshi,Hirose, Keiji,Tobe, Yoshito
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p. 1253 - 1256
(2007/10/02)
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- SYNTHESES AND RACEMIZATION VIA INTERMOLECULAR PROTOTROPY OF OPTICALLY ACTIVE ALKYLTROPYLIUM IONS. A NOVEL SCALE FOR THE KINETIC BROENSTED BASICITY OF ORGANIC SOLVENTS
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Optically active (1-methylpropyl)tropylium ion (1) and (2-bicyclooctyl)tropylium ion (2) have been synthesized.The first-order rate constants of racemization via intermolecular prototropy of 1 provide a novel scale for the kinetic Broensted basicit
- Kinoshita, Tomomi,Haga, Ken'ichi,Ikai, Keizo,Takeuchi, Ken'ichi,Okamoto, Kunio
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p. 4057 - 4060
(2007/10/02)
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- SYNTHESE ET PROPRIETES DES DEUX FORMES ENANTIOMERES DE POLY(THIOPHENES) CHIRAUX
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Chiral poly(thiophenes) obtained from two enantiomerically pure monomers can stereoselectively recognize anions used as doping agents during voltammetric cycles.
- Lemaire, M.,Delabouglise, D.,Garreau, R.,Roncali, J.
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p. 193 - 198
(2007/10/02)
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- Enantioselective Chiral Poly(thiophenes)
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Chiral poly(thiophenes) have been synthesized by electropolymerisation: they exhibit high specific rotation, stability, and conductivity and can stereoselectively recognize chiral anions used as doping agents during voltammetric cycles.
- Lemaire, Marc,Delabouglise, Didier,Garreau, Robert,Guy, Alain,Roncali, Jean
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p. 658 - 661
(2007/10/02)
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- SYNTHESIS AND CHARACTERIZATION OF CHIRAL THIOETHERS AND MERCURY(II) HALIDE COMPLEXES. THE (S)-(+)-4-ETHYL-3,4-DIHYDRO-1H-2-BENZOTHIINE MERCURY(II) CHLORIDE (1/1) ADDUCT.
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The new chiral ligand (S)-(+)-4-ethyl-3,4-dihydro-1H-2-benzothiine, (S)-(+)-EBT, and its diastereoisomeric mercury(II) chloride 1/1 complex (+) 2 have been synthesized and the u.v. and c.d. spectra measured.The stereochemistry of the r
- Bavia, Mario,Biscarini, Paolo
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p. 418 - 439
(2007/10/02)
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- Investigation of New Chiral 1,3-Oxazolidine-2-thiones: Analytical Separation and Optical Resolution of Racemic Carboxylic Acids and Amino Acids
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New chiral five-memebered heterocycles, (4S)-(4) and (4R)-4-ethyl-1,3-oxazolidine-2-thione (5), (4S)-4-isopropyl-1,3-oxazolidine-2-thione (6), and (4R,5S)-4-methyl-5-phenyl-1,3-oxazolidine-2-thione (7) have been developed.Among these heterocycles, (4R,5S)-MPOT (7) proved to be an excellent chiral reagent for analytical and efficient separation of racemic products from transformations of chiral carboxylic acids and amino acids.
- Nagao, Yoshimitsu,Kumagai, Toshio,Yamada, Shozo,Fujita, Eiichi,Inoue, Yoshinori,et al.
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p. 2361 - 2368
(2007/10/02)
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- Stereochemistry of Aliphatic Carbocations, 15. Rearrangements in 2-Arylalkyl Systems
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Phenyl shifts from secondary to primary carbon proceed with virtually complete inversion at the migration origin, regardless whether they are induced by solvolysis of the aryl sulfonate 25 or by deamination of the amines 12, 17, 26, and 43.Sequential rearrangements (Ph, CH3 and Ph, H) are likewise stereo- and regiospecific.These results strongly support the intervention of phenonium ions.In contrast, the competitive alkyl shifts (deamination only) from benzylic to primary carbon produce but a small excess of inversion (Me 27percent, Et 13percent, iPr 20percent, tBu 3percent).Obviously, benzyl cations are the predominant intermediates.
- Kirmse, Wolfgang,Guenther, Bernd-Rainer,Loosen, Karin
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p. 2140 - 2153
(2007/10/02)
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