- A simple and convenient catalytic procedure for the preparation of dithioacetals
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A simple procedure for the synthesis of cyclic and acyclic thioacetals from aldehydes is described which employs hydrogen chloride solutions generated from acetyl chloride and methanol. It was observed that the reaction could be carded out using catalytic quantities of acetyl chloride, potentially allowing acid sensitive substrates to be used under these conditions.
- Graham, Andrew E.
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- Visible-light mediated facile dithiane deprotection under metal free conditions
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Visible light mediated facile and selective dithiane deprotection under metal free conditions is developed. Eosin Y (1 mol%) proved to be an effective catalyst for the dithiane deprotection under the ambient photoredox conditions. The standard household compact fluorescent light source (CFL bulb) proved to be effective under open-air conditions in aqueous acetonitrile at room temperature. The protocol that exhibits a broad substrate scope and functional group tolerance has been shown to expand to a range of transformations for the electron-rich and -deficient thioacetals and thioketals. The synthetic utility of this protocol has also been demonstrated by gram-scale application.
- Dharpure, Pankaj D.,Bhowmick, Anindita,Warghude, Prakash K.,Bhat, Ramakrishna G.
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- Direct anodic (thio)acetalization of aldehydes with alcohols (thiols) under neutral conditions, and computational insight into the electrochemical formation of the acetals
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A versatile protocol for the production of acetals/thioacetals by means of direct electrochemical oxidation is developed here under neutral conditions, providing (thio)acetals with good functional group tolerance and a wide scope for both aldehydes and (thio)alcohols. DFT calculations reveal that direct electron transfer from the anode plays a key role in carbonyl activation during this acid free acetalization process.
- Liu, Caiyan,Shen, Yongli,Xiao, Zihui,Yang, Hui,Han, Xue,Yuan, Kedong,Ding, Yi
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p. 4030 - 4034
(2019/08/07)
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- A 2 - substituted - 1, 3 - dithiane derivative of the preparation method
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The invention provides a preparation method of a 2-substituted-1,3-dithiane derivative. The preparation method comprises the following steps: adding 1,3-dithiane (CAS:505-23-7) and 1,2-dichloroethane (DCE) or dichloromethane (DCM) into a reaction bottle, adding N-chlorosuccinimide (NCS) under ice-bath condition, and stirring for 0.5-1 h to prepare a 2-chloro-1,3-dithiane solution; and adding an aldehyde or ketone compound and a lewis acid catalyst into the above solution, and reacting to prepare the 2-substituted-1,3-dithiane derivative. By using the 1,3-dithiane solid and different types of aldehyde and keto-carbonyl compounds as raw material and using one or more of ferric trichloride, boron trifluoride diethyl etherate, methanesulfonic acid, aluminum trichloride, ferrous chloride and nickel chloride as catalysts, preparation of the 2-substituted-1,3-dithiane derivative is realized. The catalysts used in the invention are cheap and easily available, dosage of the catalysts is low and pollution of the catalysts is little. The solid raw materials used in the invention can avoid use of fetid toxic 1,3-dimercaptopropane with strong volatility, and the purpose of protecting an experimenter's body and reducing environmental pollution is realized. In addition, the preparation method has advantages of mild reaction condition, high yield, simple operation and the like.
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Paragraph 0023; 0024; 0025; 0026; 0027
(2019/06/26)
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- Thioacetalization of aldehydes and ketones catalyzed by hexabromoacetone
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Protection of p-anisaldehydewith 1,3-propanedithiol under UV irradiation without a catalyst resulted in 87% yield of 1,3-dithiane in 20 min. Addition of hexabromoacetone further reduced the reaction time and UV irradiation also accelerated the formation o
- Chaiseeda, Kittichai,Chavasiri, Warinthorn
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p. 1034 - 1039
(2017/09/08)
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- Fe-catalyzed direct dithioacetalization of aldehydes with 2-chloro-1,3-dithiane
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Present methods to synthesize 1,3-dithiane molecules require either harsh reaction conditions or highly specialized reagents. We have developed a catalytic dithioacetalization process that directly gains access to the corresponding 1,3-dithianes using aldehydes and 2-chloro-1,3-dithiane in a highly efficient manner. This methodology is beneficial due to mildness of the reaction conditions, and the dithioacetaliation process results in good to excellent yields by using 15 mol % of an iron catalyst.
- Lai, Junshan,Du, Wenbin,Tian, Lixia,Zhao, Changgui,She, Xuegong,Tang, Shouchu
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p. 4396 - 4399
(2015/01/08)
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- Aluminum hydrogen sulfate [Al(HSO4)3] as an efficient catalyst for the preparation of thioacetals
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Aluminum hydrogen sulfate, as a heterogeneous solid acid catalyst, has been used for the mild conversion of carbonyl compounds to their thioacetals using 1,2- and 1,3-dithiol under ambient conditions with short reaction times in high to excellent yield in
- Ghashang, Majid
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p. 2837 - 2842
(2013/07/26)
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- Synthesis of 1,3-dithiane and 1,3-dithiolane derivatives by tungstate sulfuric acid: Recyclable and green catalyst
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An efficient, novel, and environmentally benign procedure for the thioacetalization of aliphatic and aromatic carbonyl compounds in the presence of catalytic amounts of tungstate sulfuric acid under solvent-free conditions to afford 1,3-dithianes and 1,3-
- Karami, Bahador,Taei, Mahbubeh,Khodabakhshi, Saeed,Jamshidi, Masih
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experimental part
p. 65 - 74
(2012/07/14)
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- Palladium-catalyzed intramolecular aryl amination reaction: An expeditious approach to the synthesis of chiral benzodiazocine derivatives
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A palladium-catalyzed method for intramolecular amination of aryl bromides and iodides has been developed employing different bulky biaryl phosphanes as ligands and toluene as solvent. A variety of electron-rich aryl halide substrates have been aminated b
- Adhikary, Nirmal Das,Chattopadhyay, Partha
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experimental part
p. 1754 - 1762
(2010/06/15)
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- A mild and chemoselective dithioacetalization of aldehydes in the presence of anhydrous copper (II) sulfate
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Various aldehydes have been protected with different thiols as dithioacetals with excellent yields using anhydrous copper sulfate as a mild and chemoselective catalyst. The reaction is carried out in a solvent and/or under solvent-free conditions. The transthioacetalization of oxyacetals into dithioacetals was also achieved in an excellent yield. Copyright Taylor & Francis Group, LLC.
- Moghaddam, Firouz Matloubi,Bardajee, Ghasem Rezanejade,Oskui, Afsane Arefi
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p. 1445 - 1450
(2007/10/03)
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- Chemoselective thioacetalisation and transthioacetalisation of carbonyl compounds catalysed by tetrabutylammonium tribromide (TBATB)
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Thioacetals and thioketals of various aldehydes and ketones were obtained directly from carbonyl compounds or by a transthioacetalisation process from cyclic O,O-acetals in the presence of dithiols and a catalytic amount of tetrabutylammonium tribromide (TBATB). Chemoselective thioacetalisation of aromatic aldehydes containing an electron-donating group in the presence of an aldehyde containing an electron-withdrawing group, aldehydes in the presence of ketones, aliphatic cyclic ketones in the presence of aromatic ketones and less hindered ketones in the presence of more hindered ketones have been achieved. A cyclic acetal containing an electron-donating group has been chemoselectively transthioacetalised in the presence of an acetal having an electron-withdrawing substituent. These selectivities are due to the intrinsic reactivity of the substrate themselves and are independent of the catalyst and reaction conditions, Shorter reaction times, mild reaction conditions, stability of acid sensitive protecting groups, high efficiencies, facile isolation of the desired products and the catalytic nature of the reagent are the attractive features of the present method.
- Naik, Sarala,Gopinath, Rangam,Goswami, Mousumi,Patel, Bhisma K.
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p. 1670 - 1677
(2007/10/03)
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- Titanium reagents for the synthesis of 2-substituted benzo[b]thiophenes on the solid phase
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Titanium(IV) benzylidenes (Schrock carbenes) bearing a masked sulfur nucleophile in the ortho position were generated from thioacetals with use of low-valent titanocene complex Cp2Ti[P(OEt)3]2 and alkylidenated Merrifield resin-bound esters to give enol ethers. Treatment of the resin-bound enol ethers with a 5:5:90 mixture of TFA, TFAA, and dichloromethane led to cleavage from resin, removal of the tert- butyldimethylsilyl (TBDMS) protecting group, and concomitant cyclization to complete the traceless solid-phase synthesis (SPS) of benzothiophenes. Switching the nature of the linker from acid-stable to acid-sensitive ensured good purity.
- Roberts, Christine F.,Hartley, Richard C.
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p. 6145 - 6148
(2007/10/03)
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- Selective thioacetalization of aldehydes catalyzed by aqueous zinc tetrafluoroborate
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A wide range of cyclic dithioacetals are prepared from the corresponding aldehydes in the presence of aqueous solution of zinc tetrafluoroborate.
- Islam, Samimul,Majee, Adinath,Mandal, Tanmay,Khan
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p. 2911 - 2916
(2007/10/03)
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- Cobalt(II)chloride catalyzed chemoselective thioacetalization of aldehydes
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A mild and chemoselective dithioacetalization procedure for the protection of various aldehydes in the presence of catalytic amount of cobalt(II)chloride is described.
- De, Surya Kanta
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p. 1035 - 1036
(2007/10/03)
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- Synthesis of 2-substituted benzofurans and indoles using functionalized titanium benzylidene reagents on solid phase
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Titanium(IV) benzylidenes bearing a masked oxygen or nitrogen nucleophile in the ortho position were generated from thioacetals, using low-valent titanocene complex, Cp2Ti[P(OEt)3]2. Methylene acetal, alkyl ether, silyl ether, fluoro, tertiary amino, and N-alkyl, N-benzyl, N-prenyl, and N-silyl tert-butyl carbamate groups were tolerated in the titanium alkylidene reagents (Schrock carbenes). Aryl-chlorine bonds were stable to the titanium benzylidene functionality, but there was poor chemoselectivity for the reduction of the thioacetal in the presence of an aryl chloride. The titanium benzylidenes converted Merrifield and Wang resin-bound esters into enol ethers. The oxygen nucleophile was masked as a TMS ether, and when the resin-bound enol ethers bearing this ortho substituent were treated with 1% TFA in dichloromethane, benzofurans were released from resin in high yields. The chameleon catch strategy ensured excellent purity. In a similar way, N-alkylated and N-silylated tert-butyl carbamates were used for the synthesis of N-alkyl and N-Boc indoles, respectively. These traceless solid-phase syntheses of heterocycles are believed to involve post-cleavage modification rather than cyclative termination.
- Macleod, Calum,McKiernan, Gordon J.,Guthrie, Emma J.,Farrugia, Louis J.,Hamprecht, Dieter W.,Macritchie, Jackie,Hartley, Richard C.
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p. 387 - 401
(2007/10/03)
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- Nickel(II) chloride as an efficient and useful catalyst for chemoselective thioacetalization of aldehydes
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A wide variety of acyclic and cyclic dithioacetals can be prepared chemoselectively from the corresponding aldehydes by employing a catalytic amount of nickel(II) chloride in dry CH2Cl2-MeOH (5:1) at room temperature in good yields.
- Khan, Abu T.,Mondal, Ejabul,Sahu, Priti R.,Islam, Samimul
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p. 919 - 922
(2007/10/03)
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- Mild and efficient chemoselective protection of aldehydes as dithioacetals employing N-bromosuccinimide
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A mild and chemoselective dithioacetalization procedure for the protection of aromatic, aliphatic, and alkenyl aldehydes in presence of catalytic amount of N-bromosuccinimide under neutral conditions is described.
- Kamal, Ahmed,Chouhan, Gagan
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p. 474 - 476
(2007/10/03)
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- Novel functionalized titanium(IV) benzylidenes for the traceless solid-phase synthesis of indoles
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(matrix presented) Titanium(IV) benzylidenes bearing a masked nitrogen nucleophile in the ortho position converted Merrifield resin-bound esters into enol ethers. An unusual nitrogen protecting group, N-silylated tert-butyl carbamate, was employed. One percent TFA released N-Boc indoles in high yield and purity. N-Methyl indoles were also prepared. Cyclative termination was not required to release the chameleon catch. The first example of a carbonyl group within a titanium alkylidene reagent is reported.
- Macleod, Calum,Hartley, Richard C.,Hamprecht, Dieter W.
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- A general alternative to obtain S.S-acetals using taff, a bentonitic clay, as the catalyst
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A one-pot general alternative to prepare dithioacetals, with excellent yields, via the condensation of 1,3-propanedithiol, benzyl, and n-butyl mercapthanes with several carbonylic compounds using a bentonitic earth as the catalyst is proposed. Also, the a
- Miranda,Osnaya,Garduno,Delgado,Alvarez,Salmon
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p. 1587 - 1597
(2007/10/03)
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- COMPETITION BETWEEN ADDITION AND REDOX PROCESSES IN REACTIONS OF NITROARENES WITH LITHIUM-DITHIANES
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The reaction of 2-lithio-1,3-dithianes with nitroarenes gives 2-(or 4-)cyclohexa-3,5(or 2,5-)-diene-1-nitronate compounds (conjugate-addition products), free nitroarene radical anions (redox products), 1,3-dithianes and 2,2'-bis-(1,3-dithianes).The conjugate-addition and redox products were converted in the respective nitroaromatic compounds by oxidation in situ with O2 or DDQ.The ratio between addition and redox products increases with decrease of temperature. 2-H-2-Lithio-1,3-dithiane can give both 1,4- and 1,6-addition products, while 2-methyl- and 2-phenyl derivatives give only 1,6-addition products.A mechanism involving an s.e.t. from lithium dithianes to nitroarenes followed by various decay routes is suggested for the two radical species.
- Bartoli, Giuseppe,Dalpozzo, Renato,Grossi, Loris,Todesco, Paolo E.
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p. 2563 - 2570
(2007/10/02)
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