Showing papers on "Methyl vinyl ketone published in 2008"

Organocatalysed asymmetric Mannich reactions.

Abstract: The asymmetric Mannich reaction ranks among the most potent enantioselective and diastereoselective C–C-bond forming reactions. In recent years, organocatalysed versions of asymmetric Mannich processes have been increasingly reported and used in a rapidly growing number of applications. This tutorial review provides an overview of the recent history of the asymmetric organocatalysed Mannich reaction, including scope and limitations, and application of different catalyst systems.

Diastereo- and enantioselective hydrogenative aldol coupling of vinyl ketones: design of effective monodentate TADDOL-like phosphonite ligands.

Abstract: We report the first enantioselective reductive aldol couplings of vinyl ketones, which were achieved through the design of a novel monodentate TADDOL-like phosphonite ligand. Specifically, hydrogenation of commercially available methyl vinyl ketone (MVK) or ethyl vinyl ketone (EVK) in the presence of aldehydes 1a−7a using cationic rhodium catalysts modified by chiral TADDOL-like phosphonite ligands AP-I and AP-IV produces aldol adducts 1b−7b and 1c−7c with excellent control of relative and absolute stereochemistry. The absolute stereochemical assignments of the aldol adducts are made in analogy to that determined for the 5-bromophthalimido derivative of aldol adduct 1b and the 2-bromo-5-nitrobenzoate of 3b, which were established by single-crystal X-ray diffraction analysis using the anomalous dispersion method.

Absolute Photoionization Cross-Section of the Methyl Radical†

Abstract: The absolute photoionization cross-section of the methyl radical has been measured using two completely independent methods. The CH3 photoionization cross-section was determined relative to that of acetone and methyl vinyl ketone at photon energies of 10.2 and 11.0 eV by using a pulsed laser-photolysis/time-resolved synchrotron photoionization mass spectrometry method. The time-resolved depletion of the acetone or methyl vinyl ketone precursor and the production of methyl radicals following 193 nm photolysis are monitored simultaneously by using time-resolved synchrotron photoionization mass spectrometry. Comparison of the initial methyl signal with the decrease in precursor signal, in combination with previously measured absolute photoionization cross-sections of the precursors, yields the absolute photoionization cross-section of the methyl radical; σCH3(10.2 eV) = (5.7 ± 0.9) × 10−18 cm2 and σCH3(11.0 eV) = (6.0 ± 2.0) × 10−18 cm2. The photoionization cross-section for vinyl radical determined by photo...

Aqueous-phase ozonolysis of methacrolein and methyl vinyl ketone: a potentially important source of atmospheric aqueous oxidants

Abstract: Recent studies indicate that isoprene and its gas-phase oxidation products could contribute a considerable amount of aerosol through aqueous-phase acid-catalyzed oxidation with hydrogen peroxide (H 2 O 2 ), although the source of H 2 O 2 is unclear. The present study revealed a potentially important route to the formation of aqueous oxidants, including H 2 O 2 , from the aqueous-phase ozonolysis of methacrolein (MAC) and methyl vinyl ketone (MVK). Laboratory simulation was used to perform the atmospheric aqueous-phase ozonolysis at different pHs and temperatures. Unexpectedly high molar yields of the products, including hydroxylmethyl hydroperoxide (HMHP), formaldehyde (HCHO) and methylglyoxal (MG), of both of these reaction systems have been seen. Moreover, these yields are almost independent of pH and temperature and are as follows: (i) for MAC–O 3 , 70.3±6.3% HMHP, 32.3±5.8% HCHO and 98.6±5.4% MG; and (ii) for MVK–O 3 , 68.9±9.7% HMHP, 13.3±5.8% HCHO and 75.4±7.9% MG. A yield of 24.2±3.6% pyruvic acid has been detected for MVK–O 3 . HMHP is unstable in the aqueous phase and can transform into H 2 O 2 and HCHO with a yield of 100%. We suggest that the aqueous-phase ozonolysis of MAC and MVK can contribute a considerable amount of oxidants in a direct and indirect mode to the aqueous phase and that these compounds might be the main source of aqueous-phase oxidants. The formation of oxidants in the aqueous-phase ozonolysis of MAC and MVK can lead to substantial aerosol formation from the aqueous-phase acid-catalyzed reaction of H 2 O 2 with MAC, even if there are no other sources of oxidants.

Direct amino acid-catalyzed cascade biomimetic reductive alkylations: application to the asymmetric synthesis of Hajos–Parrish ketone analogues

Abstract: A direct amino acid-catalyzed chemo- and enantioselective process for the double cascade synthesis of highly substituted 2-alkyl-cyclopentane-1,3-diones, 2-alkyl-3-methoxy-cyclopent-2-enones and Hajos–Parrish (H–P) ketone analogs is presented via reductive alkylation chemistry. For the first time, we have developed a single-step alkylation of cyclopentane-1,3-dione with aldehydes/ketones and a Hantzsch ester through an organocatalytic reductive alkylation strategy. A direct combination of amino acid-catalyzed cascade olefination–hydrogenation and cascade Robinson annulations of cyclopentane-1,3-dione, aldehydes/ketones, a Hantzsch ester and methyl vinyl ketone furnished the highly functionalized H–P ketone analogues in good to high yields and with excellent enantioselectivities. Many of the reductive alkylation products have shown direct applications in pharmaceutical chemistry.

Dendritic Chiral Phosphine Lewis Bases-Catalyzed Asymmetric Aza-Morita–Baylis–Hillman Reaction of N-Sulfonated Imines with Activated Olefins

Abstract: A series of polyether dendritic chiral phosphine Lewis bases was synthesized, and successfully applied to the asymmetric aza-Morita–Baylis–Hillman reaction of N-sulfonated imines (N-arylmethylidene-4-methylbenzenesulfonamides) with methyl vinyl ketone (MVK), ethyl vinyl ketone (EVK), and acrolein to give the adducts in good to excellent yields along with up to 97 % ee, which are more effective than our previously reported original chiral phosphine Lewis bases. In addition, the dendrimer-supported chiral phosphine Lewis bases can be easily recovered and reused.

Palladium-Catalyzed Cyclization/Heck- and Cyclization/Conjugate-Addition-Type Sequences in the Preparation of Polysubstituted Furans

Abstract: Palladium-catalyzed heterocyclization-coupling sequences have been developed starting from buta-1,2,3-trienyl carbinols and electron-deficient alkenes. Polysubstituted furans are formed where the heterocyclic ring originates from the elements of the butatrienyl carbinol while the electron-deficient olefin is incorporated as a C-3 substituent. In most cases, the reaction proceeds via a Heck-type pathway leading to the efficient formation of 3-vinylfurans. However, couplings with methyl vinyl ketone display a divergent behavior to afford selectively either Heck- or hydroarylation-type products depending on reaction conditions.

Heterogeneous reactions of methacrolein and methyl vinyl ketone: Kinetics and mechanisms of uptake and ozonolysis on silicon dioxide

Abstract: [1] Methacrolein (MAC) and methyl vinyl ketone (MVK), two major first-generation products in the oxidation of isoprene, play important roles in tropospheric chemistry. However, little is known about their heterogeneous fate. Here we investigated the heterogeneous reactions of MAC and MVK on particles of silicon dioxide (SiO2), the major constituent of mineral dust in the troposphere, under simulated tropospheric conditions. We first investigated the adsorption and desorption processes. It was found that MAC and MVK molecules were adsorbed onto the surface of SiO2 particles by van der Waals forces and hydrogen bonding forces in a non-reactive state, and the presence of water vapor did not result in the formation of new substances but could decrease the adsorption ability by consuming isolated hydroxyl groups on the surface of SiO2 particles. The initial adsorption and desorption rates, initial uptake coefficients, and adsorption concentrations at equilibrium were determined at different relative humidities. Notably, in the desorption process, a considerable amount of MAC or MVK molecules remained on SiO2 particles in dry air but were almost completely desorbed in high-humid air. We also investigated the heterogeneous ozonolysis of MAC and MVK adsorbed onto SiO2 particles, determining product yields at different relative humidities. The heterogeneous ozonolysis of MAC and MVK adsorbed onto SiO2 particles yielded formaldehyde and methylglyoxal as the major secondary carbonyl products and formic acid and acetic acid as the major organic acid products, as in their gas-phase ozonolysis. However, the yield of two major organic peroxides, methyl hydroperoxide and hydroxymethyl hydroperoxide, was much greater in their heterogeneous ozonolysis than in their gas-phase ozonolysis. The mechanisms of heterogeneous ozonolysis of MAC and MVK onto the SiO2 surface are deduced.

Phospha-michael reactions involving p-heterocyclic nucleophiles

Abstract: P-heterocyclic γ-ketophosphonates were synthesized by the Michael reaction of methyl vinyl ketone with dibenzo-1,2-oxaphosphorine 2-oxide, 1,3,2-dioxaphosphorine 2-oxide and benzo-1,3,2-dioxaphospholane 2-oxide, respectively. In the first two cases, 50% of 1,8-diazabicyclo[5.4.0[undec-7-ene had to be used that was also required in the addition of dibenzooxaphosphorine oxide to cyclohexenone to result in the formation of the corresponding γ-ketophosphonate. The addition of dibenzooxaphosphorine oxide to less reactive 1,2-dihydrophosphinine oxide was accomplished after activation by an equimolar amount of trimethylaluminum to afford a 3-P(O)<-1,2,3,6-tetrahydrophosphinine oxide, which was subjected to catalytic hydrogenation to provide the corresponding 1,2,3,4,5,6-hexahydrophosphinine oxide. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:288–292, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20421

A One-Pot, Asymmetric Robinson Annulation in the Organic Chemistry Majors Laboratory

Abstract: The Robinson annulation is a topic of importance in the second-year organic curriculum. A one-pot, enantioselective Robinson annulation is described. The experiment is completed in two lab periods and is geared towards the second-year organic chemistry major. To our knowledge, this is the first example of a one-pot enantioselective Robinson annulation in a second-year organic lab setting. Reaction between methyl vinyl ketone and 2-methyl-1,3-cyclohexanedione in the presence of a catalytic amount of (S)-proline results in the formation of the Wieland–Miescher ketone in 75% yield and an 84:16 enantiomer ratio. The product is purified easily by silica gel chromatography, and enantioselectivity is determined by either chiral HPLC or chiral GC. The catalyst used in the reaction, (S)-proline, is an organocatalyst and is moisture- and oxygen-tolerant and nontoxic. Thus the experiment is classified by many to fall within the category of green chemistry.

Bifunctional chiral phosphine-containing Lewis base catalyzed asymmetric Morita–Baylis–Hillman reaction of aldehydes with activated alkenes

Abstract: A series of novel bifunctional chiral phosphine-containing Lewis bases were synthesized and successfully applied to the asymmetric Morita–Baylis–Hillman reaction of aldehydes with methyl vinyl ketone (MVK) and ethyl vinyl ketone (EVK) to give the corresponding adducts in moderate yields and enantioselectivities under mild reaction conditions.

A Nearly Planar Stannene with a Reactive Tin–Carbon Double Bond

Abstract: Bis(2,4,6-triisopropylphenyl)-2,7-di-tert-butylfluorenylidenestannane, Tip2Sn=CR2, an isolable stannene that displays a deep-purple colour, was synthesized by dehydrofluorination of the corresponding fluorostannane by tert-butyllithium. It exhibits the shortest Sn=C distance [2.003(5) A] and the slightest twisting around this unsaturation (10°) among the known stannenes. Its reaction with benzaldehyde according to a [2+2] cycloaddition and that with α-ethylenic aldehydes and ketones such as crotonaldehyde and methyl vinyl ketone by a [2+4] cycloaddition proceeded in near-quantitative yield. With acetone, an ene reaction occurred. The four-membered ring 1,2-oxastannacyclobutane obtained with benzaldehyde underwent a ring expansion with a second molecule of benzaldehyde to afford the six-membered ring dioxastannacyclohexane.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Synthesis of 1-Oxadecalins from Anisole Promoted by Tungsten

Abstract: The complex TpW(NO)(PMe3)(η2-anisole) is combined with acrolein or methyl vinyl ketone and various nucleophiles to generate novel chromen complexes. These complexes may be further elaborated by protonation and nucleophilic addition to generate chroman analogues with increased saturation and stereocenters. Treatment with various oxidants effects the decomplexation of the chromen.

Cross-Metathesis of Chiral N-tert-ButylsulfinylHomoallylamines: Application to the Enantioselective Synthesis ofNaturally Occurring 2,6-cis-Disubstituted Piperidines

Abstract: The synthesis of piperidine alkaloids (+)-dihydropinidine( 1), (+)-isosolenopsin ( 2A), (+)-isosolenopsin A ( 2B), and (2 R,6 R)-6-methylpipecolic acid ( 3A) hydrochlorides, based on cross-metathesisof chiral N- TERT-butylsulfinylhomoallylamines with methyl vinyl ketone, is presented.

Surface modification. II. Functionalization of solid surfaces with vinylic monomers

Abstract: A new method to functionalize surfaces of solid substrates such as glass, silicon crystals, and silica microspheres with appropriate vinylic monomers, i.e., methyl vinyl ketone, methyl acrylate, methacrolein, and acrolein, is described. The surface modification process was performed through the following sequence of reactions: (a) derivatization of the surfaces with ω-nitrile groups by interacting the substrates with SiCl 3 (CH 2 ) 3 CN; (b) subsequent reduction of the ω-nitrile groups with diborane to ω-amine groups; (c) binding of the vinylic monomers to the surfaces via the ω-amine groups. pK 1/2 of the surface primary amine groups, as determined by contact angle titration, was found to be 2-4 units lower than the pK a values of primary amine analogous in solution. Methyl vinyl ketone and methyl acrylate were covalently bound to the amine surfaces only under basic conditions via the Michael addition reaction. Methacrolein and acrolein were covalently bound to the amine surfaces under both acidic and basic conditions via two major reactions: the Michael addition reaction and Schiff base bond formation. The concentration of the aldehyde groups of the surfaces obtained by the reaction with methacrolein and acrolein was significantly higher than that obtained using the common, published method in which glutaraldehyde interacts with the amine surfaces.

Synthesis of new methyl derivatives of aza-and diazaphenanthrene

Abstract: By condensation of acetone with 2-naphthylamine and 3-(4-fluorophenyl)-1H-pyrazole-4-, pyridine-3-, quinoline-2-, quinoline-6-carbaldehyde and 4-(2-fluorobenzyloxy)benzaldehyde new 3-aryl(heteryl)-1-methylbenzo[f]quinolines were synthesized. Reactions of acetone with 6-quinolylamine and aromatic aldehydes provided 3-aryl-1-methyl-4,7-phenanthrolines. Intermediate reaction products were isolated: 4-phenyl-or (3-pyridyl)-4-(2-naphthylamino or 6-quinolylamino)butan-2-ones.

Methyl Vinyl Ketone

Abstract: [78-94-4] C4H6O (MW 70.10) [59120-04-6] InChI = 1S/C4H6O/c1-3-4(2)5/h3H,1H2,2H3 InChIKey = FUSUHKVFWTUUBE-UHFFFAOYSA-N InChI = 1/C4H6O/c1-3-4(2)5/h3H,1H2,2H3 InChIKey = FUSUHKVFWTUUBE-UHFFFAOYAV (reagent for attachment of 3-oxobutyl side chains, i.e. Michael additions;2 reagent for the annulation of cyclohexenones3) Alternate Names: MVK; 3-buten-2-one. Physical Data: fp −6 °C; bp 81.4 °C, 36.5–36.8 °C/145 mmHg, 33–34 °C/130 mmHg, 32–34 °C/60 mmHg; d (20 °C) 0.8636 g cm−3, (25 °C) 0.8407 g cm−3; nD20 1.4086; liquid with pungent odor. Solubility: sol water, methanol, ethanol, ether, acetone, glacial acetic acid; slightly sol hydrocarbons; forms binary azeotrope with water, bp 75 °C (12% water). Form Supplied in: clear liquid stabilized with 0.1% acetic acid and 0.05% or 1% hydroquinone. Handling, Storage, and Precautions: should be kept cold. Polymerizes upon standing in the pure form. Readily absorbed through skin; lachrymator; highly toxic and flammable. For best results, dry over K2CO3 and freshly distill at reduced pressure. Use in a fume hood.

Synthesis of Poly-substituted 2-Pyridones via (3+2+1) Annulation Protocol from Baylis-Hillman Adducts

Abstract: The synthesis of a substituted 2-pyridone ring is an area of continuing interest due to its abundance in many biologically important compounds containing this moiety. Although numerous papers have been reported on the synthesis of this class of compounds, development of a new and efficient synthetic procedure is still required. Recently, we reported an efficient synthetic method for poly-substituted pyridines from the combination of BaylisHillman adducts (3 carbons), activated methylene compounds (2 carbons) and ammonium acetate (1 nitrogen) via [3+2+1] annulation protocol in good yields, regioselectively. In the previous paper, we used Baylis-Hillman adducts derived from methyl vinyl ketone and obtained 2methyl pyridine derivatives. In continuation of our research, we intended to prepare the valuable poly-substituted 2pyridones by using the Baylis-Hillman adducts of methyl acrylate 1a as shown in Scheme 1. The starting material 3a was synthesized from the reaction of Baylis-Hillman acetate 1a and methyl acetoacetate (2a) in 77% yield. The ester 3a indeed produced 2-pyridone 7a, albeit in low yield (16%), along with three other products, 4a (34%), 5a (7%) and 6a (5%), when subjected to the conditions previously employed for the synthesis of pyridine derivatives (NH4OAc (3.0 equiv)/AcOH/reflux). Increasing the reaction temperature or varying the solvent (propionic or butyric acid) did not improve the results. The use of NH4Cl or NH4OH was also not effective. Fortunately, during the examinations we found that the use of excess amounts of NH4OAc afforded good yield of 7a. The reaction gave much better yield of 7a (75%), while suppressing the formation of by-products 4a (4%), 5a (12%) and 6a (5%), when 3a was heated in AcOH with 20 equiv of NH4OAc. The use of excess amounts of NH4OAc might be beneficial for the isomerization of 4a to 7a, although the reason is not clear at this stage. Encouraged by the results we prepared starting materials 3b-g similarly from ethyl acetoacetate (2b), 2,4-pentanedione (2c), methanesulfonylacetone (2d), 1,3-cyclohexanedione (2e), deoxybenzoin (2f), and 1,3-indandione (2g) in 56-85% yields. The syntheses of 7b-g were carried out by the same method for 7a and the results are summarized in Table 1. Various 2-pyridone derivatives 7b-g were synthesized in 64-82% yields including bicyclic (entry 5) and tricyclic compound (entry 7). In all cases trace amounts of the corresponding benzylidene compounds, alcohols, and benzoyl derivatives were observed on TLC, but we didn’t isolate them except entry 1 (vide supra, Scheme 1). The formation of alcohol 5a and benzoyl derivative 6a could be explained