- Gaining Insight Into Reactivity Differences Between Malonic Acid Half Thioesters (MAHT) and Malonic Acid Half Oxyesters (MAHO)
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An efficient two-step synthesis of structurally and functionally diverse thiophenol- and (cyclo)alkyl-derived malonic acid half thioesters (MAHTs) and phenol-derived malonic acid half oxyesters (MAHOs) has been achieved using cheap, readily available and easily handled starting materials. The synthesis of the MAHTs and MAHOs (the majority of which have not been previously reported) is readily scalable to afford gram quantities of product. In a hydrogen→deuterium exchange, an interesting stereoelectronic effect was observed when different aryl groups were incorporated. Significant changes in the rates of hydrogen→deuterium exchange and levels of isotope incorporation were observed. By way of example, using [2H]methanol and 4-bromophenol-derived MAHO afforded only 14 % [2H]-incorporation (9 min, k=31) whereas the corresponding 4-bromothiophenol-derived MAHT afforded 97 % [2H]-incorporation (9 min, k=208). In a benchmark procedure and comprehensive DFT study, 54 ester and thioester configurations and conformations were characterized. In the MAHT series, a sulfur-containing molecular orbital provides a path for increased delocalisation of electron density into the enol that is unavailable in MAHOs. This facilitates keto–enol tautomerisation and consequently enhances the rate and percentage of hydrogen→deuterium exchange.
- Bew, Sean P.,Stephenson, G. Richard,Rouden, Jacques,Godemert, Jeremey,Seylani, Haseena,Martinez-Lozano, Luis A.
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supporting information
p. 4557 - 4569
(2017/04/13)
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- Organocatalytic enantioselective decarboxylative aldol reaction of malonic acid half thioesters with aldehydes
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Copycat: A highly enantioselective biomimetic aldol reaction of malonic acid half thioesters with a variety of aldehydes affords optically active β-hydroxy thioesters by employing the cinchona-derived sulfonamide organocatalyst 1. The synthetic utility of this protocol was demonstrated by performing formal syntheses of the antidepressants (R)-fluoxetine, (R)-tomoxetine, (-)-paroxetine, and (R)-duloxetine. Copyright
- Bae, Han Yong,Sim, Jae Hun,Lee, Ji-Woong,List, Benjamin,Song, Choong Eui
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supporting information
p. 12143 - 12147
(2013/12/04)
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- Malonic acid half oxyesters and thioesters: Solvent-free synthesis and DFT analysis of their enols
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A much improved synthetic route to malonic acid half thioesters (MAHTs) and oxyesters (MAHOs), the easy incorporation of deuterium labeling expecially in MAHTs, and an unexpectedly large difference in enolization chemistry between MAHTs and MAHOs are repo
- Bew, Sean P.,Stephenson, G. Richard,Rouden, Jacques,Martinez-Lozano, Luis A.,Seylani, Haseena
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supporting information
p. 3805 - 3807
(2013/09/02)
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- Expanding the utility of Bronsted base catalysis: Biomimetic enantioselective decarboxylative reactions
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As a result of the low reactivity of simple esters, the use of them as nucleophiles in direct asymmetric transformations is a long-standing challenge in synthetic organic chemistry. Nature approaches this difficulty through a decarboxylative mechanism, which is used for polyketide synthesis. Inspired by nature, we report guanidine-catalyzed biomimetic decarboxylative C-C and C-N bond-formation reactions. These highly enantioselective decarboxylative Mannich and amination reactions utilized malonic acid half thioesters as simple ester surrogates. It is proposed that nucleophilic addition precedes decarboxylation in the mechanism, which has been investigated in detail through the identification of intermediates by using electrospray ionization (ESI) mass-spectrometric analysis and DFT calculations. Copyright
- Pan, Yuanhang,Kee, Choon Wee,Jiang, Zhiyong,Ma, Ting,Zhao, Yujun,Yang, Yuanyong,Xue, Hansong,Tan, Choon-Hong
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supporting information; experimental part
p. 8363 - 8370
(2011/09/13)
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- Decarboxylative ketone aldol reactions: Development and mechanistic evaluation under metal-free conditions
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(Chemical Equation Presented) Malonic acid half thioesters (MAHTs) and malonic acid half oxyesters (MAHOs) are shown to undergo decarboxylative nucleophilic addition reactions with ketone and aldehyde electrophiles in the presence of stoichiometric or catalytic quantities of triethylamine at room temperature. The ability to perform these reactions under metal-free conditions has enabled a detailed mechanistic analysis of the reaction pathway leading to the 1H NMR spectroscopic characterization of a postnucleophilic addition/predecarboxylation intermediate and experimental evidence for a reversible formation of this intermediate followed by an irreversible decarboxylation. Rate constants for each of the bond forming/bond breaking steps in the reaction pathway were also determined, casting light on the differing reactivity betweenMAHOandMAHT nucleophiles in these processes. Finally, the mechanistic insights gained through these studies have been employed in the development of a new decarboxylative coumarin synthesis.
- Blaquiere, Nicole,Shore, Daniel G.,Rousseaux, Sophie,Fagnou, Keith
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supporting information; experimental part
p. 6190 - 6198
(2009/12/24)
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- Mg2+-imidazole-catalyzed self-condensation of malonyl thioesters: Getting tuned for biomimetic polyketide synthesis?
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We report that a subtle balance of carbanion reactivity, leaving group activation, and pKa of the catalyst is required for efficient self-condensation of thiomalonates to thioacetoacetates in up to 71% yield under "biomimetic" conditions originally proposed by Kobuke and Yoshida (Tetrahedron Lett. 1978, 19, 367).
- Sakai, Naomi,Sorde, Nathalie,Matile, Stefan
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p. 845 - 851
(2007/10/03)
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- A Convenient Method for the Preparation of S-Esters of Thio Analogs of Malonic Acid
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2-Carboxyethanethioic S-esters (RSCOCH2COOH) and propanebis(thioic) S,S'-diesters (RSCOCH2COSR) were easily prepared in high yields by the direct condensation of malonic acid with thiols in the presence of ethyl polyphosphate (PPE).
- Imamoto, Tsuneo,Kodera, Masahito,Yokoyama, Masataka
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p. 2303 - 2304
(2007/10/02)
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- A CONVENIENT ONE-POT PROCEDURE FOR SYNTHESIS OF THIOL ESTERS USING MAGNESIUM ION AS A CATALYST
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Various thiol esters (R1COSR2) were prepared in high yields by treatment of 1-acylimidazole with thiols in the presence of a catalytic amount of Mg(OEt)2.Malonic half-thiol esters 1OCOCH(R3)COSR2> were also prepared in good yields by treating magnesium monoalkyl malonate 1OCOCH(R3)COOMg0.5> with carbonyl-1,1'-diimidazole followed by addition of thiols.
- Ohta, Shunsaku,Okamoto, Masao
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p. 3245 - 3246
(2007/10/02)
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