- 1,3-Dibromo-5,5-dimethylhydantoin as a Precatalyst for Activation of Carbonyl Functionality
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Activation of carbonyl moiety is one of the most rudimentary approaches in organic synthesis and is crucial for a plethora of industrial-scale condensation reactions. In esterification and aldol condensation, which represent two of the most important reactions, the susceptibility of the carbonyl group to nucleophile attack allows the construction of a variety of useful organic compounds. In this context, there is a constant need for development of and improvement in the methods for addition-elimination reactions via activation of carbonyl functionality. In this paper, an advanced methodology for the direct esterification of carboxylic acids and alcohols, and for aldol condensation of aldehydes using widely available, inexpensive, and metal-free 1,3-dibromo-5,5-dimethylhydantoin under neat reaction conditions is reported. The method is air- and moisture-tolerant, allowing simple synthetic and isolation procedures for both reactions presented in this paper. The reaction pathway for esterification is proposed and a scale-up of certain industrially important derivatives is performed.
- ?ebular, Klara,Bo?i?, Bojan ?.,Stavber, Stojan
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supporting information
(2019/08/01)
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- Oxygenation of Simple Olefins through Selective Allylic C?C Bond Cleavage: A Direct Approach to Cinnamyl Aldehydes
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A novel metal-free allylic C?C σ-bond cleavage of simple olefins to give valuable cinnamyl aldehydes is reported. 1,2-Aryl or alkyl migration through allylic C?C bond cleavage occurs in this transformation, which is assisted by an alkyl azide reagent. This method enables O-atom incorporation into simple unfunctionalized olefins to construct cinnamyl aldehydes. The reaction features simple hydrocarbon substrates, metal-free conditions, and high regio- and stereoselectivity.
- Liu, Jianzhong,Wen, Xiaojin,Qin, Chong,Li, Xinyao,Luo, Xiao,Sun, Ao,Zhu, Bencong,Song, Song,Jiao, Ning
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supporting information
p. 11940 - 11944
(2017/09/20)
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- Domino-Hydroformylation/Aldol Condensation Catalysis: Highly Selective Synthesis of α,β-Unsaturated Aldehydes from Olefins
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A general and highly chemo-, regio-, and stereoselective synthesis of α,β-unsaturated aldehydes by a domino hydroformylation/aldol condensation reaction has been developed. A variety of olefins and aromatic aldehydes were efficiently converted into various substituted α,β-unsaturated aldehydes in good to excellent yields in the presence of a rhodium phosphine/acid-base catalyst system. In view of the easy availability of the substrates, the high atom-efficiency, the excellent selectivity, and the mild conditions, this method is expected to complement current methodologies for the preparation of α,β-unsaturated aldehydes.
- Fang, Xianjie,Jackstell, Ralf,Franke, Robert,Beller, Matthias
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supporting information
p. 13210 - 13216
(2016/02/19)
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- Synthesis of α,β-unsaturated aldehydes based on a one-pot phase-switch dehydrogenative cross-coupling of primary alcohols
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An efficient one-pot ruthenium-catalyzed hydrogen-transfer strategy for a direct access to α,β-unsaturated aldehydes has been developed. The employment of enolates prepared in situ from alcohols avoided handling unstable aldehydes and provided a very appealing route to different cinnamaldehydes substituted in position 2. A silica-grafted amine was used as phase-switch tag leading to a selective one-pot process in favor of cross-dehydrogenative coupling products.
- Mura, Manuel G.,De Luca, Lidia,Taddei, Maurizio,Williams, Jonathan M. J.,Porcheddu, Andrea
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supporting information
p. 2586 - 2589
(2014/06/09)
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- Microwave-assisted organocatalytic cross-aldol condensation of aldehydes
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An environmentally benign organocatalytic cross-aldol condensation of aldehydes under microwave irradiation in the absence of solvent is described. Using pyrrolidine as a catalyst, an efficient and sustainable atom economic method was developed for the cross-aldol condensation of various aldehydes with excellent results. Among the products, jasmine aldehyde, α-hexyl cinnamaldehyde and cyclamen aldehyde, three compounds of great industrial demand, were synthesised.
- Limnios, Dimitris,Kokotos, Christoforos G.
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p. 4496 - 4499
(2013/05/09)
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- A general route to α-alkyl (E)-α,β-unsaturated aldehydes
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Bis(trimethylsilyl)-tert-butylaldimines 3 react with aldehydes in the presence of zinc bromide at room temperature to give, after hydrolysis, the desired α-alkyl α,β-ethylenic aldehydes in good yield and with very high E stereoselectivity. The reaction was believed to proceed via the α-silyl β-siloxyimines 4.
- Lahmar, Nour,Aatar, Jamaa,Ayed, Ta?cir Ben,Amri, Hassen,Bellassoued, Moncef
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p. 3018 - 3026
(2007/10/03)
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- Supported choline hydroxide (ionic liquid) as heterogeneous catalyst for aldol condensation reactions
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Choline hydroxide was used as a basic catalyst for aldol condensation reactions to produce new C-C bonds between several ketones and aldehydes. Choline supported on MgO exhibits higher TOF values than other well known basic catalysts in these reactions.
- Abello, Sonia,Medina, Francisco,Rodriguez, Xavier,Cesteros, Yolanda,Salagre, Pilar,Sueiras, Jesus E.,Tichit, Didier,Coq, Bernard
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p. 1096 - 1097
(2007/10/03)
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- Aldol Condensations on Solid Catalysts: A Cooperative Effect between Weak Acid and Base Sites
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An amorphous aluminophosphate (ALPO) catalyst containing weak acid and base centers can carry out the aldol condensation of heptanal with benzaldehyde at much higher rates and selectivities than conventional solid acid (amorphous or crystalline aluminosil
- Climent,Corma,Fornes,Guil-Lopez,Iborra
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p. 1090 - 1096
(2007/10/03)
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- Acid-base bifunctional catalysts for the preparation of fine chemicals: Synthesis of jasminaldehyde
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Jasminaldehyde was prepared by condensation between benzaldehyde and heptanal. Large-pore acid zeolites (HY and Beta), mesoporous aluminosilicate (Al MCM-41), and amorphous aluminophospates (ALPO) were used as catalysts. The results indicated that zeolites showed lower activity and selectivity than mesoporous aluminosilicate (Al MCM-41). These results were attributed to the confinement effects of the reactants and products inside of the voids of the microporous materials, which lead to the preferential formation of the heptanal self-condensation product, as well as to a fast deactivation of the catalyst. However, the amorphous aluminophosphate (ALPO) which possesses weaker acid sites than zeolites and MCM-41, but combines acidic and basic sites, showed the maximum activity and selectivity to jasminaldehyde. This finding was explained on the basis of the acid-base bifunctional character of the ALPO catalyst. The role of the weak acid sites is to activate benzaldehyde by protonation of the carbonyl group, favoring then the attack of the enolate heptanal intermediate generated on the relatively weak basic sites of ALPO.
- Climent,Corma,Garcia,Guil-Lopez,Iborra,Fornes
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p. 385 - 393
(2007/10/03)
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- Use of mesoporous MCM-41 aluminosilicates as catalysts in the preparation of fine chemicals: A new route for the preparation of jasminaldehyde with high selectivity
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α-n-Amylcinnamaldehyde (Jasminaldehyde) has been prepared with high selectivity and using low ratios of benzaldehyde/heptanal by means of mesoporous molecular sieve catalysts and a process which involves the acetalization of heptanal with methanol, followed, in the same pot, by a slow hydrolysis of dimethylacetal and the aldolic condensation of the two aldehydes as the final step. A large pore zeolite (Beta) as well as mesoporous silica-aluminas with regular pore sizes such as MCM-41 and SAM have been used as catalysts. The results indicate that mesoporous silica-aluminas with a very narrow range of pore diameter such as MCM-41 are the most adequate catalysts to produce in one pot the three consecutive reactions, avoiding in a very large extent the self-condensation of heptanal and undesired consecutive reactions. This new route allows us to achieve Jasminaldehyde with high selectivity and with a relative high global reaction rates. The influence of the concentration of acid sites on MCM-41, reaction temperature, and molar ratio of the reactants have been also studied.
- Climent,Corma,Guil-Lopez,Iborra,Primo
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- Synthesis of α,β-Unsaturated Carbonyl Compounds by Titanium Tetraalkoxide-Induced Aldol Condensation under Neutral Conditions
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Aldehydes and ketones, when treated with titanium tetraalkoxides in a hydrocarbon solvent at 20-140 deg C, undergo aldol condensation to give α,β-unsaturated carbonyl compounds.To avoid Meerwein-Ponndorf-Verley type reduction of the carbonyl compounds, titanium tetra-tert-butoxide is used, if the reaction is carried out at higher temperatures.In all other cases titanium tetraisopropoxide can be successfully employed.The outlined procedure offers the possibility of performing aldol condensations under neutral conditions.
- Mahrwald, Rainer,Schick, Hans
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p. 592 - 595
(2007/10/02)
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- Alkylation of Lithium Trialkylalkynylborates with Benzo-1,3-dithiolium Fluoroborate
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Lithium trialkylalkynylborates react in a stereoselective fashion with benzo-1,3-dithiolium fluoroborate to give vinylboranes which on oxidation yield protected 3-oxo-aldehydes and on hydrolysis give protected αβ-unsaturated aldehydes; the hydrolysis is highly selective giving rise eventually to stereospecifically defined αβ-unsaturated aldehydes by a novel process.
- Pelter, Andrew,Rupani, Pushpa,Stewart, Peter
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p. 164 - 165
(2007/10/02)
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