- Reductive deoxygenation using hydridozirconium enolates: A new synthesis of α,β-unsaturated esters
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An unusual new reaction of Cp2ZrHCl transforms β-ketoesters into α,β-unsaturated esters in one step and provides a useful alternative to the traditional, three-step process of reduction, mesylation/tosylation, and elimination.
- Godfrey,Ganem
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- Biocatalytic synthesis of chiral cyclic γ-oxoesters by sequential C-H hydroxylation, alcohol oxidation and alkene reduction
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A three-step biocatalytic procedure is described for the conversion of methyl and ethyl cyclopentene- and cyclohexenecarboxylates into both the enantiomers of the corresponding chiral 3-oxoesters, which are useful building blocks for the synthesis of active pharmaceutical ingredients. The allylic hydroxylation of the starting cycloalkenecarboxylates is carried out by using R. oryzae resting cells entrapped in alginate beads, in acetate buffer solution at 25 °C. The oxidation of the intermediate allylic alcohols to unsaturated ketones, performed by the laccase/TEMPO system, and the ene-reductase mediated hydrogenation of the alkene bond were carried out in the same reaction vessel in a sequential mode at 30 °C. Being entirely biocatalytic, our multistep procedure provides considerable advantages in terms of selectivity and environmental impact over reported chemical methods.
- Brenna, Elisabetta,Crotti, Michele,Gatti, Francesco G.,Monti, Daniela,Parmeggiani, Fabio,Pugliese, Andrea,Tentori, Francesca
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supporting information
p. 5122 - 5130
(2017/11/09)
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- Stereo- and chemoselective cross-coupling between two electron-deficient acrylates: An efficient route to (Z, E)-muconate derivatives
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A Ru-catalyzed direct oxidative cross-coupling reaction of acrylates was developed. It offers a straightforward and atom-economical protocol for the synthesis of functionalized (Z,E)-muconate derivatives in moderate to good yields with good stereo- and chemoselectivities. The conjugated muconates bearing differentiable terminal functionality can be selectively transformed into versatile synthetic intermediates widely used in organic synthesis.
- Hu, Xu-Hong,Zhang, Jian,Yang, Xiao-Fei,Xu, Yun-He,Loh, Teck-Peng
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supporting information
p. 3169 - 3172
(2015/03/30)
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- Direct ortho-thiolation of arenes and alkenes by nickel catalysis
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The direct thiolation of arenes and alkenes with diaryl disulfides was developed by nickel catalysis. The reaction displayed exceptional compatibility with a wide range of functional groups to regioselectively give the diaryl sulfides and alkenyl sulfides in high yields.
- Lin, Cong,Li, Danyang,Wang, Binjie,Yao, Jinzhong,Zhang, Yuhong
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supporting information
p. 1328 - 1331
(2015/03/14)
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- Iridium-catalyzed direct C-H amidation with weakly coordinating carbonyl directing groups under mild conditions
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An iridium-catalyzed direct C-H amidation of weakly coordinating substrates, in particular of those bearing ester and ketone groups, under very mild conditions has been developed. The observed high reaction efficiency was achieved by the combined use of acetic acid and lithium carbonate as additives. Copyright
- Kim, Jinwoo,Chang, Sukbok
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supporting information
p. 2203 - 2207
(2014/03/21)
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- Iridium(I)-catalyzed vinylic C-H borylation of 1-cycloalkenecarboxylates with bis(pinacolato)diboron
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Ir(i)-catalyzed C-H borylation of 1-cycloalkenecarboxylic derivatives with bis(pinacolato)diboron affords various alkenylboronates with functional groups in excellent yields. This reaction was also used in a one-pot borylation/Suzuki-Miyaura cross-coupling procedure.
- Sasaki, Ikuo,Doi, Hana,Hashimoto, Toshiya,Kikuchi, Takao,Ito, Hajime,Ishiyama, Tatsuo
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supporting information
p. 7546 - 7548
(2013/08/23)
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- Isothiourea-mediated asymmetric O- to C-carboxyl transfer of oxazolyl carbonates: Structure-selectivity profiles and mechanistic studies
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The structural motif within a series of tetrahydropyrimidine-based isothioureas necessary for generating high asymmetric induction in the asymmetric Steglich rearrangement of oxazolyl carbonates is fully explored, with crossover and dynamic 19F NMR experiments used to develop a mechanistic understanding of this transformation. Copyright
- Joannesse, Caroline,Johnston, Craig P.,Morrill, Louis C.,Woods, Philip A.,Kieffer, Madeleine,Nigst, Tobias A.,Mayr, Herbert,Lebl, Tomas,Philp, Douglas,Bragg, Ryan A.,Smith, Andrew D.
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p. 2398 - 2408
(2012/03/27)
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- A mild, catalytic and efficient Nazarov cyclization mediated by phosphomolybdic acid
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A mild, selective and efficient Nazarov cyclization of divinyl ketones catalyzed by phosphomolybdic acid (PMA) is described. The process demonstrates a broad substrate scope with functional group tolerance under short reaction times. PMA supported on silica gel is more efficient than the bulk catalyst and is recycled up to three times without significant activity loss.
- Murugan, Kaliyappan,Srimurugan, Sankareswaran,Chen, Chinpiao
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supporting information; experimental part
p. 1127 - 1129
(2010/06/18)
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- Efficient preparation of α,α-dialkyl-α-(phenylselanyl) acetates and α,β-unsaturated esters from the corresponding α,α-dialkyl-α-cyanoacetates by a lithium naphthalenide induced reductive selenenylation process
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An array of α,α-dialkyl-α-(phenylselanyl)acetates has been synthesized very efficiently from readily available α,α- dialkyl-α-cyanoacetates, by use of lithium naphthalenide induced reductive α-selenenylation as a key operation. Moreover, the selanyl esters thus generated in situ could be converted further, in a one-pot treatment with hydrogen peroxide and acetic acid, into the corresponding α,β- unsaturated esters in moderate to high yields. The C=C bond formation was highly regio- and/or diastereoselective in some cases. Georg Thieme Verlag Stuttgart.
- Ko, Yen-Chun,Zhu, Jia-Liang
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p. 3659 - 3665
(2008/09/19)
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- An expedient, stereoselective synthesis of highly functionalized cyclic compounds
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New thiophosphates containing functionalized cyclic ketone derivatives as ligands have been stereoselectively (prepared from readily available starting materials. Full axial stereoselectivity of the NaBH)4 (reduction) of the carbonyl group in thiophosphates providing the corresponding thiols or sulfides has been demonstrated. The sulfides have been transformed into new functionalized cyclic Baylis-Hillman type adducts of defined configuration. The prospects for the useful synthetic application of these adducts appear to be very promising.
- Krawczyk, Ewa,Owsianik, Krzysztof,Skowronska, Aleksandra,Wieczorek, Michal,Majzner, Wieslaw
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p. 1753 - 1767
(2007/10/03)
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- Photoinduced free radical chemistry of the acyl tellurides: Generation, inter- and intramolecular trapping, and ESR spectroscopic identification of acyl radicals
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Acyl tellurides are prepared in good to excellent yield by the reaction of sodium aryl tellurides with acyl chlorides, or mixed anhydrides, and are found to be moderately air-stable substances. In contrast to previous literature reports, acyl tellurides of aryl and vinyl carboxylic acids are found to be excellent sources of acyl radicals on photolysis with a simple white light source. The acyl radicals so generated may be trapped intermolecularly by dichalcogenides, or by TEMPO in excellent yield. Trapping by N-tert-butyl-α-phenyl nitrone produces a stable nitroxide radical which has been characterized by ESR spectroscopy. The very efficient trapping of acyl radicals by acyl tellurides themselves is demonstrated by a crossover experiment. Acyl tellurides are shown to participate in very efficient radical cyclization reactions onto alkenes with the formation of five-, six-, and eight-membered rings. The immediate products of the cyclizations onto alkenes are α-[(aryltelluro)methyl] ketones and the chemistry of these relatively unstable species is briefly described. Treatment with hydrogen peroxide affords α-methylene ketones in high yield. When elimination of the aryl telluro group is not possible the α-[(aryltelluro)methyl] ketones are stable species that may subsequently be employed in further radical chain reactions, for example with tributyltin hydride and methyl acrylate. Cyclization onto alkynes yields α-[(aryltelluro)methylene] ketones which are stable species and which take part in substitution reactions with higher order cuprates or with diphenyl diselenide.
- Crich, David,Chen, Chen,Hwang, Jae-Taeg,Yuan, Hongwei,Papadatos, Aristotle,Walter, Robert I.
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p. 8937 - 8951
(2007/10/02)
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- Synthesis of 4,7-Disubstituted Spirobenzofuran-2(3H)-cyclohexanes
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A general synthetic strategy was designed for the preparation of 7-substituted-4-methoxy- and 4-hydroxyspiro 5 and 6 (Figure 1) using successive, regioselective heteroatom-facilitated aromatic lithiation reactions and subsequent reaction with various electrophiles.
- Bradbury, Barton J.,Sindelar, Robert D.
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p. 1827 - 1833
(2007/10/02)
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- Preparation des organozinciques derives de l'α-bromomethyl acrylate d'ethyle et de ses homologues
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The preparation of the bromozinc derivatives of various α-bromoalkyl acrylates (aliphatic and alicyclic) results in high yields when carried out on 30 mesh activated granular zinc, between 14 and 20 deg C in ethereal solvents (THF, DME, ether).Under these conditions duplication can be minimized (5-15 percent) especially with t-butyl acrylates.These α-functional allylic orgazinc derivatives have been characterized by hydrolysis and coupling with benzaldehyde.
- Alami, Najat El,Belaud, Chantal,Villieras, Jean
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- Preparation of organic acids and/or esters
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Carboxylic acids and/or esters are prepared by converting the STR1 moiety in a 1-substituted 2,2-trihaloethanol, or derivative wherein X represents halogen and R is hydrogen or an acyl group to an organic acid and/or ester grouping of the formula STR2 wherein R' is hydrogen or alkyl of 1 to 6 carbon atoms, in the process which comprises reacting the 1-substituted 2,2,2-trihaloethanol or acylated derivative with molecular oxygen in the presence of a catalyst comprising a complex of a transition metal having an atomic number from 21-30, 39-48 or 57-80 and at least one molecule of a ligand containing trivalent nitrogen, phosphorus, arsenic or antimony. This reaction is carried out in a reaction medium comprising an alcohol or aqueous alcohol having 1 to 6 carbon atoms optionally containing an alkali metal, said alcoholic solvent also serving as a reactant source when carboxylic acid esters are formed.
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- Reactions of Electron Deficient Dienes with (Acylmethylene)triphenylphosphoranes: One-Pot-Three-Step-Reactions
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3a-Azaazulenes (1, 7) react with (acylmethylene)triphenylphosphoranes (2) in a one-pot-three-step-synthesis (Michael addition, intramolecular addition, Wittig elimination) to form cyclohexadiene 1,4-derivatives (3, 8).The course of the reaction is determined by steric requirements which is shown by ethyl 3-isopropylbenzoate (11) formation from ethyl 1,3-cyclohexadiene-1-carboxylate (9) and phosphorane 2b.
- Flitsch, Wilhelm,Gesing, Ernst Rudolf F.
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p. 3146 - 3153
(2007/10/02)
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