- Latent Nucleophilic Carbenes
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Using DFT and ab initio calculations, we demonstrate that noncyclic formamidines can undergo thermal rearrangement into their isomeric aminocarbenes under rather mild conditions. We synthesized the silylformamidine, for which the lowest activation energy in this process was predicted. Experimental studies proved it to serve as a very reactive nucleophilic carbene. The reactions with acetylenes, benzenes, and trifluoromethane proceeded via insertion into sp, sp2, and spCH bonds. The carbene also reacted with the functional groups, such as CHO, COR, and CN at double or triple bonds, displaying high mobility of the trimethylsilyl group. The obtained silylformamidine can be considered as a latent nucleophilic carbene. It can be prepared in bulk quantities, stored, and used when the need arises. Calculation results predict similar behavior for some other silylated formamidines and related compounds.
- Marchenko, Anatoliy,Koidan, Georgyi,Hurieva, Anastasiya,Shvydenko, Kostiantyn,Rozhenko, Alexander B.,Rusanov, Eduard B.,Kyrylchuk, Andrii A.,Kostyuk, Aleksandr
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p. 373 - 385
(2021/12/27)
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- Monodentate Transient Directing Group Enabled Pd-Catalyzed Ortho-C-H Methoxylation and Chlorination of Benzaldehydes
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We report Pd-catalyzed ortho-C-H methoxylation and chlorination of benzaldehydes by employing monodentate transient directing groups (TDGs) as an alternative strategy to bidentate TDGs. More importantly, a single crystal of benzaldehyde imine ortho-cyclopalladium intermediate was successfully obtained, and its structure was unambiguously determined by X-ray diffraction, which clearly showed that it was a binuclear palladium species bridged by a pyridone ligand. The utility of this approach was further demonstrated through the synthesis of key intermediates of natural products and drugs.
- Li, Feng,Zhou, Yirong,Yang, Heng,Wang, Ziqi,Yu, Qinqin,Zhang, Fang-Lin
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supporting information
p. 3692 - 3695
(2019/05/24)
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- Pd-Catalyzed, ortho C-H Methylation and Fluorination of Benzaldehydes Using Orthanilic Acids as Transient Directing Groups
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The direct, Pd-catalyzed ortho C-H methylation and fluorination of benzaldehydes have been accomplished using commercially available orthanilic acids as transient directing groups. In these reactions, the 1-fluoro-2,4,6-trimethylpyridinium salts can be either a bystanding F+ oxidant or an electrophilic fluorinating reagent. An X-ray crystal structure of a benzaldehyde ortho C-H palladation intermediate was obtained using triphenylphosphine as the stabilizing ligand.
- Chen, Xiao-Yang,Sorensen, Erik J.
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supporting information
p. 2789 - 2792
(2018/03/08)
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- Stable TEMPO and ABNO Catalyst Solutions for User-Friendly (bpy)Cu/Nitroxyl-Catalyzed Aerobic Alcohol Oxidation
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Two solutions, one consisting of bpy/TEMPO/NMI and the other bpy/ABNO/NMI (bpy =2,2′-bipyridyl; TEMPO = 2,2,6,6-tetramethylpiperidine N-oxyl, ABNO = 9-azabicyclo[3.3.1]nonane N-oxyl; NMI = N-methylimidazole), in acetonitrile are shown to have good long-term stability (≥1 year) under air at 5 °C. The solutions may be combined in appropriate quantities with commercially available [Cu(MeCN)4]OTf to provide a convenient catalyst system for the aerobic oxidation of primary and secondary alcohols.
- Steves, Janelle E.,Stahl, Shannon S.
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p. 11184 - 11188
(2015/11/18)
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- N-Functionalized Amino Acids Promoted Aerobic Copper-Catalyzed Oxidation of Benzylic Alcohols in Water
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Instead of traditional N,N-bidentate ligands, N-functionlized amino acids were used as powerful N,O-bidentate ligands in aerobic copper/TEMPO-catalyzed system for promoting oxidation of benzylic alcohols. Under the optimized reaction conditions, a wide range of primary and secondary benzylic alcohols have been efficiently converted into aldehydes and ketones with good to excellent yields in water.
- Zhang, Guofu,Lei, Jie,Han, Xingwang,Luan, Yuxin,Ding, Chengrong,Shan, Shang
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p. 779 - 784
(2015/03/30)
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- Practical organic solvent-free Cu(OAc)2/DMAP/TEMPO-catalyzed aldehyde and imine formation from alcohols under air atmosphere
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A highly efficient and practical organic solvent-free Cu(OAc)2/DMAP/TEMPO catalyst system for the selective aerobic oxidation of benzylic and allylic alcohols to aldehydes and phenones under an ambient air atmosphere was reported. A wide range of functional groups such as phenolic hydroxyl, amino, and methylthio are compatible with the catalyst system. The organic solvent-free aerobic oxidative imine synthesis from benzyl alcohol and amines was also achieved via the newly developed Cu(OAc)2/DMAP/TEMPO catalyst. 100 g-scale reactions for aldehyde and imine formation were achieved with over 90% yield using 0.5 mol% catalyst loading in 36 hours, presenting a potential valuable protocol for both economical and environmental considerations. This journal is
- Guan, Mingyu,Wang, Chao,Zhang, Jingyu,Zhao, Yingsheng
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p. 48777 - 48782
(2014/12/10)
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- Tetra-n-butylammonium bromide: A simple but efficient organocatalyst for alcohol oxidation under mild conditions
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A simple but efficient organocatalytic system with 5 mol% tetra-n-butylammonium bromide (TBAB) as the catalyst has been identified for alcohol oxidation for the first time. This organocatalytic system is compatible with a broad range of benzylic/allylic alcohols with various catalytically reactive groups. Besides, it shows excellent selectivity for secondary benzylic alcohols over aliphatic alcohols, and good selectivity over the primary benzylic alcohol site in 4-(1-hydroxyethyl)benzyl alcohol. Thus, the features of simplicity, high efficiency, selectivity and mildness of reaction conditions associated with this TBAB organocatalytic system suggest its potential for widespread use in synthetic chemistry.
- Ma, Xinyi,Li, Zhongfeng,Liu, Feijie,Cao, Shengli,Rao, Honghua
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supporting information
p. 1741 - 1746
(2014/06/09)
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- In situ generation of active species "nO" for the aerobic oxidative deprotection of aldoximes catalyzed by FeCl3/TEMPO
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A simple and efficient aerobic oxidative deoximation system, using molecular oxygen as the green oxidant and FeCl3/TEMPO as the catalyst, is developed for a wide range of aldoximes. Notably, nitric oxide (NO), an active species for aerobic oxidation reactions, is assumed to be generated in situ from the cleavage of oximes and further confirmed by the existence of a large quantity of NO3- by Ionic Chromatography (IC).
- Zhang, Guofu,Wen, Xin,Wang, Yong,Han, Xingwang,Luan, Yuxin,Zheng, Lebin,Ding, Chengrong,Cao, Xiaoji
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p. 22918 - 22921
(2013/11/19)
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- Regioselective formylation of 1,3-disubstituted benzenes through in situ lithiation
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A facile method of regioselective formylation of disubstituted benzene via in situ deprotonation/metalation using n-BuLi/TMEDA/DIPA has been developed. Effect of different electron withdrawing and electron donating substituents in 1,3-interrelated aromatic system was studied; the metalation mostly occurred at the 2-position to afford the desired products in high yields.
- Wang, Le,Wang, Yan,Guo, Fangxu,Zheng, Yue,Bhadury, Pinaki S.,Sun, Zhihua
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supporting information
p. 6053 - 6056
(2013/10/22)
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- Highly practical copper(I)/TEMPO catalyst system for chemoselective aerobic oxidation of primary alcohols
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Aerobic oxidation reactions have been the focus of considerable attention, but their use in mainstream organic chemistry has been constrained by limitations in their synthetic scope and by practical factors, such as the use of pure O2 as the oxidant or complex catalyst synthesis. Here, we report a new (bpy)CuI/TEMPO catalyst system that enables efficient and selective aerobic oxidation of a broad range of primary alcohols, including allylic, benzylic, and aliphatic derivatives, to the corresponding aldehydes using readily available reagents, at room temperature with ambient air as the oxidant. The catalyst system is compatible with a wide range of functional groups and the high selectivity for 1° alcohols enables selective oxidation of diols that lack protecting groups.
- Hoover, Jessica M.,Stahl, Shannon S.
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supporting information; experimental part
p. 16901 - 16910
(2011/12/04)
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- Solvent-free oxidation of alcohols with potassium persulphate in the presence of bronsted acidic ionic liquids
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An efficient conversion of alcohols to aldehydes was achieved using potassium persulphate and 3-methylimidazolinium methane sulfonate. Copyright Taylor & Francis Group, LLC.
- Chaskar,Bhandari,Patil,Sharma,Mayeker
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experimental part
p. 366 - 370
(2009/04/07)
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- N-methyl morpholine chlorochromate: An efficient reagent for oxidation of primary and secondary alcohols to carbonyl compounds
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Instantaneous generation of N-methyl morpholine chlorochromate (NMMCC) is an efficient reagent for oxidation of primary and secondary alcohols to the corresponding carbonyl compounds. The comparison of reaction time and product yield was studied with novel NMMCC and other chlorochromate reagents and shows that the presented method requires less reaction time with good yield at laboratory temperature. The synthesis of reagent, formation of toxic and hazardous chromylchloride have been avoided, and also use of NMMCC under microwave irradiation for oxidation leads to fast reaction time and success of the strategy. Copyright Taylor & Francis Group, LLC.
- Chandrappa,Sadashiva,Rangappa
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p. 2638 - 2645
(2008/12/22)
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- Direct oxidation of N-benzylamides to aldehydes or ketones by N-bromosuccinimide
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A simple and efficient approach for the one-pot transformation of N-benzylamides to aldehydes or ketones under mild conditions was reported. All the 20 substrates gave moderate to excellent oxidative yields under the optimized conditions. Our study may provide a new approach for the one-pot synthesis of aldehydes or ketones from the corresponding amides. Copyright Taylor & Francis Group, LLC.
- Wang, Guangjun,Li, Zhengwei,Ha, Chengyong,Ding, Ke
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p. 1629 - 1637
(2008/09/21)
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- A fast and efficient deprotection of aldehydes from acylals using a Wells-Dawson heteropolyacid catalyst (H6P2W 18O62 · 24H2O)
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A rapid and efficient method for the deprotection of aldehyde 1,1-diacetates is described. The reaction was carried out using a Wells-Dawson type catalyst supported on silica. The catalyst, used in 1% molar quantity, is easily recoverable and reusable and maintains the activity after its use in four consecutive reaction batches. The yield of the deprotection was 92-100% (15 examples including nitrobenzaldehyde 1,1-diacetates). Reaction conditions involve short times and the use of toluene as the solvent; isolation is simple and the products are nearly pure.
- Romanelli,Autino,Baronetti,Thomas
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p. 3909 - 3914
(2007/10/03)
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- Halex reactions of aromatic compounds catalysed by 2-azaallenium, carbophosphazenium, aminophosphonium and diphosphazenium salts: A comparative study
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An increasing number of biologically active compounds in the pharma and agro-chemical sector contain carbon fluorine bonds. One of the most common methods to introduce fluorine into intermediates is the well-investigated halogen-exchange reaction, in which chloro- and bromoaromatics activated towards nucleophilic substitution, react with a fluoride source to yield the corresponding fluoroarenes. In general, the reaction is supported by phase-transfer catalysts. The use of a new class of very active phase-transfer catalysts gives the possibility of substituting even halogens with weak activation giving a convenient access to interesting compounds that are not available so far and opening up new synthetic routes in Halex chemistry. Our new classes of catalysts, CNC+ (1a), PNC+ (2a) and several different approaches presented by other groups are described and experimental results discussed.
- Pleschke, Axel,Marhold,Schneider,Kolomeitsev,R?schenthaler
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p. 1031 - 1038
(2007/10/03)
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- Aminophosphonium compounds
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The present invention relates to compounds of the formula in which one, two or three of the radicals R1, R2, R3and R4are where m and n are an integer from 1 to 10, R5, R6, R7and R8are, independently of one another, identical or different and are a straight-chain or branched alkyl radical having 1 to 10 carbon atoms, and the remaining radical(s) R1to R4are or —NR9R10, where R9and R10are identical or different and are a straight-chain or branched alkyl radical having 1 to 10 carbon atoms, and X?is an inorganic or organic anion or an equivalent of a multiply charged inorganic or organic anion. The invention further relates to mixtures of substances comprising compounds of the formula (1), to a process for preparing the compounds of the formula (1) and to the use thereof.
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- Isoquinoline compound melanocortin receptor ligands and methods of using same
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The invention relates to melanocortin receptor ligands and methods of using the ligands to alter or regulate the activity of a melanocortin receptor. The invention further relates to tetrahydroisoquinoline aromatic amines that function as melanocortin receptor ligands and as agents for controlling cytokine-regulated physiologic processes and pathologies, and combinatorial libraries thereof.
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- Process for the continuous production of aromatic aldehydes
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A process for the continuous production of aromatic aldehydes of the formula (1) STR1 in which Ar is an aryl radical, R1, R2 and R3 independently of one another are hydrogen, fluorine, chlorine or bromine atoms, in which dichloromethyl-substituted aromatics of the formula (2) STR2 in which Ar, R1, R2, R3 have the above meanings, are continuously hydrolyzed with an aqueous solution of one or more catalysts of the formula (3) in which M is a transition metal selected from the group comprising iron, nickel, copper, chromium, thallium, zinc and mercury, X is F, Cl, Br, I, OH, SO4, PO4 or NO3, and n depending on the oxidation state of the transition metal M is the number 1, 2, 3 or 4, in a concentration of from about 1 to about 50%, based on the weight of water in the catalyst solution, at temperatures of from about 70° to about 160° C.
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- 'HALEX' FLUORINATION OF CHLORINATED BENZALDEHYDES AND BENZOYL CHLORIDES
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Spray-dried potassium fluoride, suspended in sulpholane at 220 degC, converted 2,4- and 2,6-dichlorobenzaldehyde into the corresponding difluoroaldehydes (yields ca. 65percent).Small amounts of the mono-substituted products (2-chloro-4-fluoro- + 4-chloro-2-fluorobenzaldehyde, and 2-chloro-6-fluoro-benzaldehyde, respectively) were also produced.Similar treatment of the 3,4-dichloro-analogue gave 3-chloro-4-fluorobenzaldehyde (yield 98percent, conversion 68percent), but 2- and 4-chlorobenzaldehyde gave very poor yields (ca. 5percent) of the 2- and 4-fluoro-derivatives. 2-Fluoro-, 4-fluoro- and 3-chloro-4-fluorobenzoyl fluoride were obtained (yields 60-65percent) by heating the corresponding chlorobenzoyl chlorides with potassium fluoride in sulpholane.
- Banks, R. Eric,Mothersdale, Kevin N.,Tipping, Anthony E.,Tsiliopoulos, Efthimios,Cozens, Barry J.,et al.
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p. 529 - 537
(2007/10/02)
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- Process for nucleophilic fluoroalkylation of aldehydes
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Aryl difluoromethyl sulfone adds to alkehydes under phase transfer conditions to give novel substituted alcohols of the general formula wherein R is an aryl, cycloaliphatic, sec- or tert-aliphatic, or heterocyclic group and Ar is an aryl group. The substituted alcohols of formula I are of particular utility as intermediates in the synthesis of a variety of useful end products. For example, the products of formula I may be utilized in desulfonylation reactions, oxidation reactions and fluorination reactions.
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