- Radical Reactions Induced by Visible Light in Dichloromethane Solutions of Hünig's Base: Synthetic Applications and Mechanistic Observations
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β-(3-Iodopropoxy)-substituted α,β-unsaturated lactams, lactones, and cycloalkenones (eight examples) underwent reductive radical reactions in a dichloromethane solution of N,N-diisopropylethylamine (Hünig's base) upon irradiation with visible light (λ=419 nm). Apart from plain reduction reactions (hydro-de-iodination), a significant degree of cyclization was observed in three cases. In parallel to the conversion of the substrates, the formation of intensely colored by-products was observed. Based on mass spectrometric evidence and upon comparison with known compounds, the by-products were identified as cyanine dyes. Their formation supports the hypothesis that irradiation of dichloromethane solutions of Hünig's base leads to the formation of radicals, which in turn can either initiate a radical reaction or combine with cyanine precursors. It was shown by deuterium-labelling experiments, that one equivalent of dichloromethane is incorporated into the cyanine dyes and that the reductive quenching of radical intermediates is at least partially due to hydrogen abstraction from the solvent. As a consequence, a reductive cyclization of the starting materials is favored in CD2Cl2solutions as shown for two β-(3-iodopropoxy)-substituted tetronates, which underwent in dichloromethane almost exclusive reduction, but gave predominantly the cyclization products in CD2Cl2.
- B?hm, Alexander,Bach, Thorsten
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- Iodine-catalyzed synthesis of β-keto enol ethers
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The use of iodine, as a catalyst for the synthesis of β-keto enol ethers at room temperature is reported. The use of iodine, as a catalyst for the synthesis of β-keto enol ethers at room temperature is reported.
- Bhosale, Rajesh S.,Bhosale, Sidhanath V.,Bhosale, Sheshanath V.,Wang, Tianyu,Zubaidha
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- Cyclization of 5-hexynoic acid to 3-alkoxy-2-cyclohexenones
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The one-pot cyclization of 5-hexynoic acid to produce 3-alkoxy-2- cyclohexenones proceeds in good yields (58-90%). 3-Hexynoic acid was converted to its acyl chloride with the aid of oxalyl chloride and was cyclized to 3-chloro-2-cyclohexenone upon addition of indium(III) chloride. Subsequent addition of alcohol nucleophiles led to the desired 3-alkoxy-2-cyclohexenones.
- Hylden, Anne T.,Uzelac, Eric J.,Ostojic, Zeljko,Wu, Ting-Ting,Sacry, Keely L.,Sacry, Krista L.,Xi, Lin,Jones, T. Nicholas
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- B(C6F5)3-catalyzed synthesis of β-keto enol ethers from β-diketones
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Efficient and practical synthesis of β-keto enol ethers from diketones catalyzed by B(C6F5)3 at room temperature has been described. Georg Thieme Verlag Stuttgart.
- Chandrasekhar,Srinivasa Rao,Ramakrishna Reddy
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- Reversible chemoselective transetherification of vinylogous esters using Fe-catalyst under additive free conditions
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An additive/Br?nsted acid/base free, highly efficient and chemoselective transetherification of electron deficient vinylogous esters and water mediated de-alkylation using an earth-abundant Fe-catalyst under very mild reaction conditions is described. This reaction is highly selective to primary alcohols over secondary alcohols, has good functional group tolerance, is scalable to gram scale and a purification free sequential transetherification in a continuous flow mode is demonstrated.
- Parvathalu, Nenavath,Agalave, Sandip G.,Mohanta, Nirmala,Gnanaprakasam, Boopathy
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p. 3258 - 3266
(2019/03/26)
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- Rapid and Multigram Synthesis of Vinylogous Esters under Continuous Flow: An Access to Transetherification and Reverse Reaction of Vinylogous Esters
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An environmentally benign approach for the synthesis of vinylogous esters from 1,3-diketone and its reverse reaction under continuous-flow has been developed with alcohols in the presence of inexpensive Amberlyst-15 as a catalyst. This methodology is highly selective and general for a range of cyclic 1,3-dicarbonyl compounds which gives a library of linear alkylated and arylated vinylogous esters in good to excellent yield under solvent and metal free condition. Furthermore, the long-time experiment in a continuous-flow up to 40 h afforded 8.0 g of the vinylogous ester with turnover number (TON) = 28.6 and turnover frequency (TOF) = 0.715 h-1 using Amberlyst-15 as a catalyst. Furthermore, a continuous-flow sequential transetherification of vinylogous esters with various alcohols has been achieved in high yield. Reversibly, this vinylogous ester was deprotected or hydrolyzed into ketone using environmentally benign water as a solvent and Amberlyst-15 as a catalyst under continuous-flow process.
- Mohanta, Nirmala,Chaudhari, Moreshwar B.,Digrawal, Naveen Kumar,Gnanaprakasam, Boopathy
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p. 1034 - 1045
(2019/05/24)
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- Iron(III) tosylate in the preparation of dimethyl and diethyl acetals from ketones and β-keto enol ethers from cyclic β-diketones
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An efficient method for conversion of ketones to their corresponding dimethyl and diethyl acetals and of cyclic β-diketones into β-keto enol ethers using Fe(OTs)3 as a catalyst is described. Copyright Taylor & Francis Group, LLC.
- Mansilla, Horacio,Afonso, Maria M.
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p. 2607 - 2618
(2008/12/22)
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- An efficient conversion of β-diketones into β-keto enol ethers with P2O5/SiO2 under solvent-free conditions
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P2O5/SiO2 was found to be an efficient reagent for converting cyclic-β-diketones into their corresponding β-keto enol ethers at room temperature under solvent-free conditions.
- Cui, Zhen-Shui,Zhang, Zhan-Hui,Liu, Shu-Fen
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p. 390 - 392
(2007/10/03)
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- 3'-ALKOXY SPIROCYCLIC TETRAMIC AND TETRONIC ACIDS
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The invention relates to novel 3'-alkoxy spirocyclic tetramic and tetronic acids of formula (I), wherein A, B, D, Q1, Q2, G, W, X, Y and Z are as defined in the description, to several methods and intermediate products for the production and the use thereof in the form of pesticides and/or herbicides and/or microbicides, to selective herbicide agents, 3'-alkoxy spirocyclic tetramic and tetronic acids and to at least one compound which improves cultivated plants compatibility.
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Page/Page column 166-167
(2008/06/13)
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- SYNTHESIS OF SPIROETHERS USING RADICAL CYCLISATIONS
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A variety of spiroether products, including one bis-spiro compound, are avaible via a simple radical cyclisation route.
- Middleton, Donald S.,Simpkins, Nigel S.,Begley, Michael J.,Terrett, Nicholas K.
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p. 545 - 564
(2007/10/02)
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