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Selective cleavage of ketals and acetals under neutral, anhydrous conditions using triphenylphosphine and carbon tetrabromide
A convenient method for the selective removal of ketal and acetal protection under mild, neutral, anhydrous conditions using PPh3 and CBr4 is described.
Johnstone, Craig,Kerr, William J.,Scott, James S.
p. 341 - 342
(1996)
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REACTIVITY OF THE 1-t.BUTYLTHIO-3-METHOXY-1-ALKENES TOWARDS METALATING AGENTS, I. REGIOSELECTIVE DEPROTONATION AT EITHER ONE OF THE TWO OLEFINIC SITES OF THE Z-ISOMERS
THF solutions of the title Z-isomers (with the exception of the propenyl compound) at -78 degC produce either(i) the 1-metalated derivatives when treated with potassium t.butoxide and n.butyllithium or (ii) the 2-lithiated derivatives when sec.butyllithium is the metalating agent.Both metalated derivatives become new equivalents of the hypothetical anions I and II respectively.
Ekogha, C. Bibang Bi,Ruel, O.,Julia, S. A.
p. 4825 - 4828
(1983)
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Efficient Transformation of Methyl Propargyl Ethers into α,β-Unsaturated Ketones
Methyl propargyl ethers, obtained from carbonyl compounds by successive treatment with an acetylide and MeI, were easily converted to the corresponding α,β-unsaturated ketone by regioselective hydration of acetylenic moiety followed by elimination of methanol under the catalytic action of Au(III).
Fukuda, Yukitoshi,Utimoto, Kiitiro
p. 2013 - 2015
(1991)
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Characterization of initial reaction intermediates in heated model systems of glucose, glutathione, and aliphatic aldehydes
To understand the effect of lipid degradation on Maillard formation of meaty flavors, initial reaction intermediates in model systems of glucose–glutathione with hexanal, (E)-2-heptenal, or (E,E)-2,4-decadienal were identified by HPLC–MS and by NMR. Besides Amadori compounds, hemiacetals and thiazolidines via addition of sulfhydryl to carbonyl or to the conjugated olefinic bond were found. Concentrations of all intermediates increased with reaction time while degradation of the intermediates with a glutathione moiety helped formation of thiazolidines with cysteinylglycine. The unsaturated aldehydes (E)-2-heptenal and (E,E)-2,4-decadienal exhibited high reactivity against glucose for glutathione, yielding higher levels of intermediate compounds than from glucose. Heating prepared intermediates reversibly released the original aldehydes, which caused various compounds formed by retro-aldol, oxidation, etc. to react with H2S and NH3. Among them, formation pathways including 3-nonen-2-one, 2-hexanoylfuran, and six dialkylthiophenes (e.g., 2-ethyl-5-(1-methylbutyl)thiophene) were proposed for the first time.
Wang, Tianze,Zhen, Dawei,Tan, Jia,Xie, Jianchun,Cheng, Jie,Zhao, Jian
(2019/09/12)

Cationic Co(I)-intermediates for hydrofunctionalization reactions: Regio- A nd enantioselective cobalt-catalyzed 1,2-hydroboration of 1,3-dienes
Much of the recent work on catalytic hydroboration of alkenes has focused on simple alkenes and styrene derivatives with few examples of reactions of 1,3-dienes, which have been reported to undergo mostly 1,4-additions to give allylic boronates. We find that reduced cobalt catalysts generated from 1,n-bis-diphenylphosphinoalkane complexes [Ph2P-(CH2)n-PPh2]CoX2; n = 1-5) or from (2-oxazolinyl)phenyldiarylphosphine complexes [(G-PHOX)CoX2] (G = 4-substituent on oxazoline ring) effect selective 1,2-, 1,4-, or 4,3-additions of pinacolborane (HBPin) to a variety of 1,3-dienes depending on the ligands chosen. Conditions have been found to optimize the 1,2-additions. The reactive catalysts can be generated from the cobalt(II)-complexes using trimethylaluminum, methyl aluminoxane, or activated zinc in the presence of sodium tetrakis[(3,5-trifluoromethyl)phenyl]borate (NaBARF). The complex, (dppp)CoCl2, gives the best results (ratio of 1,2-to 1,4-addition >95:5) for a variety of linear terminal 1,3-dienes and 2-substituted 1,3-dienes. The [(PHOX)CoX2] (X = Cl, Br) complexes give mostly 1,4-addition with linear unsubstituted 1,3-dienes, but, surprisingly, selective 1,2-additions with 2-substituted or 2,3-disubstituted 1,3-dienes. Isolated and fully characterized (X-ray crystallography) Co(I)-complexes, (dppp)3Co2Cl2 and [(S,S)-BDPP]3Co2Cl2, do not catalyze the reaction unless activated by a Lewis acid or NaBARF, suggesting a key role for a cationic Co(I) species in the catalytic cycle. Regio- A nd enantioselective 1,2-hydroborations of 2-substituted 1,3-dienes are best accomplished using a catalyst prepared via activation of a chiral phosphinooxazoline-cobalt(II) complex with zinc and NaBARF. A number of common functional groups, among them,-OBn,-OTBS,-OTs, N-phthalimido-groups, are tolerated, and er's > 95:5 are obtained for several dienes including 1-alkenylcycloalk-1-enes. This operationally simple reaction expands the realm of asymmetric hydroboration to provide direct access to a number of nearly enantiopure homoallylic boronates, which are not readily accessible by current methods. The resulting boronates have been converted into the corresponding alcohols, potassium trifluororoborate salts, N-BOC amines, and aryl derivatives by C-BPin to C-aryl transformation.
Duvvuri, Krishnaja,Dewese, Kendra R.,Parsutkar, Mahesh M.,Jing, Stanley M.,Mehta, Milauni M.,Gallucci, Judith C.,Rajanbabu
p. 7365 - 7375
(2019/05/16)

Acyl/aroyl Meldrum's acid as an enol surrogate for the direct organocatalytic synthesis of α,β-unsaturated ketones
The operationally simple, robust and straightforward organocatalytic protocol is developed for the synthesis of E-selective α,β-unsaturated ketones. The method utilizes simple and easily accessible starting materials such as Meldrum's acid, carboxylic acid, aldehyde and simple bifunctional amine catalyst. The tandem organocatalytic process utilizes acyl/aroyl Meldrum's acid as an enol surrogate for the effective Doebner-Knoevenagel type condensation reactions. A wide variety of aldehydes, carboxylic acids and base sensitive functional groups are well tolerated under the mild reaction conditions.
Khopade, Tushar M.,Warghude, Prakash K.,Mete, Trimbak B.,Bhat, Ramakrishna G.
supporting information
p. 197 - 200
(2018/12/13)

An access to α, β-unsaturated ketones via dual cooperative catalysis
A dual cooperative organocatalytic approach for the synthesis of α, β-unsaturated ketones is described. This one pot transformation is realized via a domino Knoevenagel-Michael-retro Michael reaction sequence. Various aliphatic ketones reacted smoothly with aromatic as well as aliphatic aldehydes in presence catalytic amount of Meldrum's acid and bifunctional amine. The highlights of this protocol are the easy availability of catalysts, high selectivity, and functional group tolerance. The reaction proved to highly E-selective with no side products emanating from self-condensation, unlike the base-mediated reactions.
Syamala, Lakshmi V.R. Babu,Khopade, Tushar M.,Warghude, Prakash K.,Bhat, Ramakrishna G.
supporting information
p. 88 - 91
(2018/12/05)

Design, synthesis and antimycobacterial activities of 1-methyl-2-alkenyl- 4(1H)-quinolones
A series of 23 new 1-methyl-2-alkenyl-4(1H)quinolones have been synthesized and evaluated in vitro for their antimycobacterial activities against fast growing species of mycobacteria, such as Mycobacterium fortuitum, M. smegmatis and M. phlei. The compounds displayed good to excellent inhibition of the growth of the mycobacterial test strains with improved antimycobacterial activity compared to the hit compound, evocarpine. The most active compounds, which possessed chain length of 11-13 carbons at position-2 displayed potent inhibitory effects with an MIC value of 1.0 mg/L. In a human diploid embryonic lung cell line, MRC-5 cytotoxicity assay, the alkaloids showed weak to moderate cytotoxic activity. Biological evaluation of these evocarpine analogues on the less pathogenic fast growing strains of mycobacteria showed an interesting antimycobacterial profile and provided significant insight into the structure-activity relationships.
Wube, Abraham A.,Hüfner, Antje,Thomaschitz, Christina,Blunder, Martina,Kollroser, Manfred,Bauer, Rudolf,Bucar, Franz
experimental part
p. 567 - 579
(2011/03/17)

Palladium/benzoquinone-catalyzed electrochemical oxidation of alcohols under anaerobic conditions
Primary and secondary alcohols are oxidized to aldehydes and ketones, respectively, under anaerobic conditions in DMF at 80°C, in the presence of a base and catalytic amounts of Pd(OAc)2 and p-benzoquinone. The latter oxidizes the transient Pd(0) formed in the catalytic cycle to Pd(II) and p-hydroquinone is re-oxidized electrochemically. Georg Thieme Verlag Stuttgart.
Amatore, Christian,Cammoun, Chama,Jutand, Anny
p. 2173 - 2178
(2008/02/10)

Gold-catalyzed efficient formation of alkenyl enol esters/carbonates from trimethylsilylmethyl-substituted propargyl esters/carbonates
A gold-catalyzed efficient method for the preparation of alkenyl enol esters/carbonates is developed. Besides the mild reaction conditions and high catalytic efficiency, the excellent E-selectivity of the nonenolic double bond is remarkable.
Wang, Shaozhong,Zhang, Liming
p. 4585 - 4587
(2007/10/03)

ORGANOCATALYSTS AND METHODS OF USE IN CHEMICAL SYNTHESIS
The present invention pertains generally to compositions comprising organocatalysts that facilitate stereo-selective reactions and the method of their synthesis and use. Particularly, the invention relates to metal-free organocatalysts for facilitation of stereo--selective reactions, and the method of their synthesis and use. These compounds have the structure of the Formulas (I) and (II). Where X is independently selected from CH2, N-Ra, O, S or C=O; Y is CH2, N-Ra, O, S or C=O, with the proviso that at least one of X or Y is CH2, and preferably both of X and Y are CH2; Ra is H, an optionally substituted C1-C12 alkyl, preferably an optionally substituted C1-C6alkyl including a C3-C6 cyclic alkyl group, or an optionally substituted aryl group, preferably an optionally substituted phenyl group; Rb is H, an optionally substituted C1-C12 alkyl, preferably an optionally substituted C1-C6 acyclic or a a C3-C6 cyclic alkyl group, CHO, N(Me)O, CO(S)Ra or the group of Formula (III). Where Rc and Rd are each independently H, F, C1, an optionally substituted C1-C20 alkyl, preferably an optionally substituted C1-C12 alkyl, more preferably a C1-C6 alkyl, and an optionally substituted aryl group, or together Rc and Rd form an optionally substituted carbocyclic or optionally substituted heterocyclic ring; R1 is OH, OR, NR'R", NHC(=O)R, NHSO2R; R2 is H, F, C1, an optionally substituted C1-C20 alkyl, preferably an optionally substituted C1-C6 alkyl, an optionally substituted aryl group or a =O group (which establishes a carbonyl group with the carbon to which =O is attached; R3 is H, OH, F, C1, Br, I, Cl, an optionally substituted C1-C20 alkyl, alkenyl or alkynyl ("hydrocarbyl") group, preferably an optionally substituted C1-C6 alkyl, or an optionally substituted aryl, such that the carbon to which R3 is attached has an R or S configuration; R is H, an optionally substituted C1-C20 alkyl, preferably an optionally substituted C1-C6 alkyl, or an optionally substituted aryl group, R' and R" are each independently H, an optionally substituted C1-C20 alkyl group, preferably an optionally substituted C1-C6 alkyl, or an optionally substituted aryl group; or together R' and R" form an optionally substituted heterocyclic, preferably a 4 to 7 membered optionally substituted heterocyclic group or an optionally substituted heteroaryl ring with the nitrogen to which R' and R" are attached; and wherein said compound is free from a metal catalyst.
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Page/Page column 64-65; 119-120

(2010/02/15)

L-proline-catalyzed one-pot three-component reaction for the synthesis of β-alkoxy ketones
β-Alkoxy ketones were prepared by a one-pot three-component reaction of aliphatic aldehydes, ketones, and alcohols catalyzed by L-proline. Steric effects on the reaction were studied with substituted ketones, aldehydes, and alcohols, and the results indicate that reactions employing methyl ketones, α-unsubstituted aliphatic aldehydes and methanol produce the β-alkoxy ketones in the best yields when L-proline is used as the catalyst. The reaction mechanism is discussed. Georg Thieme Verlag Stuttgart.
Dodda, Rajasekhar,Zhao, Cong-Gui
p. 3238 - 3242
(2008/09/17)

A novel pyrrolidine imide catalyzed direct formation of α,β-unsaturated ketones from unmodified ketones and aldehydes
(Chemical Equation Presented) A method for direct, stereoselective preparation of (E)-α,β-unsaturated ketones from ketones and aldehydes, promoted by a novel pyrrolidine imide organocatalyst, has been developed in moderate to high yields. Unlike the Claisen-Schmidt condensation and Lewis acid catalyzed tandem aldol-dehydration processes, this method provides mild reaction conditions to access α,β-unsaturated ketones from simple, unmodified ketones.
Wang, Wei,Mei, Yujiang,Li, Hao,Wang, Jian
p. 601 - 604
(2007/10/03)

A new protocol for a regioselective aldol condensation as an alternative convenient synthesis of β-ketols and α,β-unsaturated ketones
A general and convenient synthesis of β-ketols and α,β-alkenones has been achieved by a Knoevenagel condensation of a β-ketoacid with an aldehyde in aqueous medium. Saponification of a β-ketoester by an aqueous KOH 10% solution gives the potassium salt of the β-ketoacid, which is condensed in situ with an aldehyde at pH 7.8-8.0, at 60 °C for 5-6 h. The intermediate β-ketocarboxylate is smoothly decarboxylated in the reaction medium, giving the β-ketol in high yield (75-90%). Acidification of the reaction mixture at pH 1 and heating at 70 °C under vigorous stirring for 6 h, leads directly to the corresponding α,β-unsaturated ketone in good yield (65-75%).
Kourouli, Therapia,Kefalas, Panagiotis,Ragoussis, Nikitas,Ragoussis, Valentine
p. 4615 - 4618
(2007/10/03)

Proline-catalyzed asymmetric aldol reactions between ketones and alpha-unsubstituted aldehydes.
[reaction: see text] With this communication we extend the methodology of proline-catalyzed direct asymmetric aldol reactions to include alpha-unsubstituted aldehydes as acceptors. This important aldehyde class gives the corresponding aldols in 22-77% yield and up to 95% ee when the reactions are performed in pure acetone or in ketone/chloroform mixtures. On the basis of these results we have developed a concise new synthesis of (S)-ipsenol.
List,Pojarliev,Castello
p. 573 - 575
(2007/10/03)

Wittig reactions in the ionic solvent [bmim][BF4]
The ionic salt [bmim][BF4] is an attractive solvent for Wittig reactions, allowing both easier separation of alkenes from Ph3PO together with eficient reuse to the solvent.
Boulaire, Virginie Le,Gree, Rene
p. 2195 - 2196
(2007/10/03)

[3 + 4] Annulation of α,β-unsaturated acylsilanes with enolates of α,β-unsaturated methyl ketones: Scope and mechanism
Reactions of the E and Z isomers of (β-(trimethylsilyl)acryloyl)(tert- butyl)dimethylsilanes with lithium enolate of α,β-unsaturated methyl ketones at -80 to -30 °C afford cis-5,6- and trans-5,6-disubstituted 3- cyclohepetenones, respectively. The same [3 + 4] annulation is observed in the reaction of (β-(tri-n-butylstannyl)acryloyl)silanes. The annulation products are readily transformed into 4-cycloheptene-1,3-dione by treatment with NBS or mCPBA. The observed sterospecificity in the annulation is explained by the reaction pathway that involves an anionic oxy-Cope rearrangement of 1,2-divinylcyclopropanediol intermediate generated via Brook rearrangement of the 1,2-adduct of a lithium enolate. Isolation of vinylcyclopropanol derivative from the reaction of (β-(tri-n- butylstannyl)acryloyl)silanes with lithium enolate of 2'-bromoacetophenone and its transformation into cycloheptenone derivative with LDA provide strong support for the proposed mechanism. Further support is obtained from the reactions of 1,2-divinylcyclopropyl acetates with 2 equiv of MeLi affording cycloheptenones stereospecifically. Also, β-alkyl-substituted acryloylsilanes and cycloalkenylcarbonysilanes are found to participate in the [3 + 4] annulation.
Takeda, Kei,Nakajima, Akemi,Takeda, Mika,Okamoto, Yasushi,Sato, Taku,Yoshii, Eiichi,Koizumi, Toru,Shiro, Motoo
p. 4947 - 4959
(2007/10/03)

Isomerization of alkynemono-ols catalyzed by palladium(0) complex and diols
Isomerization of alkynemono-ols occurred by the catalysis of Pd2(dba)3 * CHCl3 (1) + iPr3P + HOCH2CH2OH.Palladium hydride active species were supposed to be formed in situ by the oxidative addition of diols to 1 as determined bu 1H NMR spectra.
Lu, Xiyan,Ji, Jianguo,Guo, Cheng,Shen, Wei
p. 259 - 266
(2007/10/02)

COBALT(II) CHLORIDE CATALYSED CONDENSATION OF ACETOACETATE WITH ENOLISABLE ALDEHYDES
Enolisable aldehydes and methyl acetoacetate react in the presence of cobalt(II) chloride (catalytic) to give the corresponding α,β-unsaturated carbonyl compound in excellent yields.Non enolisable aldehydes do not react under these conditions.A catalytic cycle for these reactions has been proposed by involving the intermediacy of a cobalt(III) enol complex of aldehydes.
Iqbal, Javed,Srivastava, Rajiv Ranjan
p. 1663 - 1666
(2007/10/02)

Alkylation of Allylic Derivatives. 17. Cross-Coupling Reactions of Diallylic Pivalates with Butyl- and Phenylcopper Reagents
Cross coupling (Z)-1-phenyl-1,4-pentadien-3-yl pivalate (cis-1-OPiv) with LiCuBu2, LiCu(CN)Bu, LiCuPh2 and LiCu(CN)Ph gives only the fully conjugated γ-coupling product.With LiCuBr2 substantial loss of double-bond configuration occures to give primarily the all-trans coupling product.With other cuprates, no detectable loss of double-bond configuration was observed.Cross coupling (Z)-3-(2-phenylethenyl)-2-cyclohexen-yl pivalate (cis-18-OPiv) with LiCuBu2, LiCuPh2, and LiCu(CN)Ph gives only α coupling product; with LiCu(CN)Bu, a mixture of α, γ, and ε coupling product was obtained.Cross coupling with LiCuBu2 results in loss of double-bond configuration in the α-alkylation product.With other cuprates, no loss of double-bond configuratiuon was detected in the α and γ coupling product.These results have profound mechanistic implications, which are discussed.The relationship between structure and reactivity was also investigated.A variety of diallylic pivalates (1-5-OPiv) were prepared and cross coupled with LiCuBu2, LiCu(CN)Bu, LiCuPh2, and LiCu(CN)Ph.Generally, coupling occurs at the least-substituted allylic system; mechanistic implications are discussed.
Underiner, Ted L.,Goering, Harlan L.
p. 2563 - 2572
(2007/10/02)

ISOMERAZATION OF PROPARGYLIC ALCOHOLS CATALYZED BY AN IRIDIUM COMPLEX
α,β-Enones were synthesized by the isomerization of propargylic alcohols catalyzed by an iridium pentahydride complex.
Ma, Dawei,Lu, Xiyan
p. 2109 - 2112
(2007/10/02)

α-ENONE BY THE REACTION OF ALDEHYDE AND α-BROMOKETONE WITH TRI-n-BUTYLSTIBINE
α-Enones were readily obtained from the reaction of α-bromoketone with aldehydes mediated by tri-n-butylstibine.
Huang, Yao-Zeng,Chen, Chen,Shen, Yanchang
p. 501 - 510
(2007/10/02)

Crossed aldol-type reactions catalyzed by rhodium complexes
Crossed aldol-type reactions of enol trimethylsilyl ethers with aldehydes and ketones are smooth when carried out with a catalytic amount of a rhodium complex, Rh4(CO)12 or X (X=PF6 and ClO4; COD=cycloocta-1,5-diene, DPPB=1,4-bis(diphenylphosphino)butane), under neutral conditions.A suitable catalyst enables the isolation of three different types of aldol reaction product, β-trimethylsiloxy ketones, β-hydroxy ketones, and α,β-unsaturated ketones.Rh4(CO)12 and ClO4 also catalyze the reaction of enol trimethylsilyl ethers with acetals or ketals, whereas PF6 does not.When ClO4 is used as the catalyst, this type of aldol reaction is extended to the one-pot synthesis of trisubstituted furans from enol trimethylsilyl ether and α-trimethylsiloxy acetal.
Sato, Susumu,Matsuda, Isamu,Izumi, Yusuke
p. 223 - 238
(2007/10/02)

THE FIRST EXAMPLE OF ALDOL REACTIONS BETWEEN TRIMETHYLSILYL ENOL ETHERS AND ALDEHYDES BY THE AID OF RHODIUM COMPLEX
Crossed aldol reaction of trimethylsilyl enol ether with aldehyde is successfully performed with the aid of catalytic amount of rhodium complex, +X- (X = PF6 and ClO4) or Rh4(CO)12, under neutral conditions.
Sato, Susumu,Matsuda, Isamu,Izumi, Yusuke
p. 5517 - 5520
(2007/10/02)

PALLADIUM-CATALYZED ACYLATION OF ORGANOZINCS AND OTHER ORGANOMETALLICS AS A CONVENIENT ROUTE TO KETONES
The reaction of organozincs with acyl chlorides catalyzed by palladium-phosphine complexes, e.g., Pd(PPh3)4, provides a highly general and convinient route to ketones.
Negishi, Ei-ichi,Bagheri, Vahid,Chatterjee, Sugata,Luo, Fen-Tair,Miller, Joseph A.,Stoll, A. Timothy
p. 5181 - 5184
(2007/10/02)