- Bis(trifluoromethanesulfonimide) (BSI): Acidity and application to hydrofunctionalization as a Br?nsted acid catalyst
-
A binaphthyl derivative, bearing bis(trifluoromethanesulfonimide) (BSI) moiety, was developed as a novel Br?nsted acid. Computational prediction of the pKa value of BSI indicated its classification as a strong Br?nsted acid. BSI catalyzed the h
- Takagi, Ryukichi,Sakai, Yuichiro,Duong, Duyen Thi
-
-
- Aryl Boronic Acid Catalysed Dehydrative Substitution of Benzylic Alcohols for C?O Bond Formation
-
A combination of pentafluorophenylboronic acid and oxalic acid catalyses the dehydrative substitution of benzylic alcohols with a second alcohol to form new C?O bonds. This method has been applied to the intermolecular substitution of benzylic alcohols to form symmetrical ethers, intramolecular cyclisations of diols to form aryl-substituted tetrahydrofuran and tetrahydropyran derivatives, and intermolecular crossed-etherification reactions between two different alcohols. Mechanistic control experiments have identified a potential catalytic intermediate formed between the aryl boronic acid and oxalic acid.
- Estopi?á-Durán, Susana,Donnelly, Liam J.,Mclean, Euan B.,Hockin, Bryony M.,Slawin, Alexandra M. Z.,Taylor, James E.
-
supporting information
p. 3950 - 3956
(2019/02/16)
-
- Visible-Light-Induced C-O Bond Formation for the Construction of Five- and Six-Membered Cyclic Ethers and Lactones
-
Visible-light-induced intramolecular C-O bond formation was developed using 2,4,6-triphenylpyrylium tetrafluoroborate (TPT), which allows the regiocontrolled construction of cyclic ethers and lactones. The reaction is likely to proceed through the single-electron oxidation of the phenyl group, followed by the formation of a benzylic radical, thus preventing a competing 1,5-hydrogen abstraction pathway. Detailed mechanistic studies suggest that molecular oxygen is used to trap the radical intermediate to form benzyl alcohol, which undergoes cyclization. This new approach serves as a powerful platform by providing efficient access to valuable five- and six-membered cyclic ethers and lactones with a unified protocol.
- Im, Honggu,Kang, Dahye,Choi, Soyeon,Shin, Sanghoon,Hong, Sungwoo
-
supporting information
p. 7437 - 7441
(2018/11/27)
-
- Visible light-promoted ring-opening functionalization of unstrained cycloalkanols via inert C-C bond scission
-
Described herein is a novel, useful, visible light-promoted ring-opening functionalization of unstrained cycloalkanols. Upon scission of an inert cyclic C-C σ-bond, a set of medium- and large-sized rings are readily brominated under mild reaction conditio
- Wang, Dongping,Mao, Jincheng,Zhu, Chen
-
p. 5805 - 5809
(2018/07/13)
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- Indium Catalyzed Hydrofunctionalization of Styrene Derivatives Bearing a Hydroxy Group with Organosilicon Nucleophiles
-
Hydrofunctionalization is one of the most important transformation reactions of alkenes. Herein, we describe the development of an indium-triiodide-catalyzed hydrofunctionalization of alkenes bearing a hydroxy group using various types of organosilicon nucleophiles. Indium triiodide was the most effective catalyst, whereas typical Lewis acids such as TiCl4, AlCl3, and BF3·OEt2 were ineffective. Many functional groups were successfully introduced, and these resulted in yields of 31-86%. Various styrene derivatives were also applicable to this reaction. Mechanistic investigation revealed that the present hydrofunctionalization proceeded through Br?nsted acid-catalyzed intramolecular hydroalkoxylation of alkenes followed by InI3-catalyzed substitution reaction of cyclic ether intermediates.
- Kita, Yuji,Yata, Tetsuji,Nishimoto, Yoshihiro,Yasuda, Makoto
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p. 740 - 753
(2018/01/28)
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- Cyclic ether synthesis from diols using trimethyl phosphate
-
Cyclic ethers have been effectively synthesized via the intramolecular cyclization of diols using trimethyl phosphate and NaH. The present cyclization could proceed at room temperature to produce 5-7 membered cyclic ethers in good to excellent yields. Substrates possessing a chiral secondary hydroxy group were transformed into the corresponding chiral cyclic ethers along with the retention of their stereochemistries.
- Asai, Shota,Kato, Maho,Monguchi, Yasunari,Sajiki, Hironao,Sawama, Yoshinari
-
supporting information
p. 4787 - 4790
(2017/07/06)
-
- Niobium-Catalyzed Intramolecular Addition of O-H and N-H Bonds to Alkenes: A Tool for Hydrofunctionalization
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A convenient, versatile, and easy to handle intramolecular hydrofunctionalization of alkenes (C-O and C-N bonds formation) is reported using a novel niobium-based catalytic system. This atom economic and eco-friendly methodology provides an additional synthetic tool for the straightforward formation of valuable building blocks enabling molecular complexity. Various pyran, furan, pyrrolidine, piperidine, lactone, and lactam derivatives as well as spirocyclic compounds are produced in high yields and selectivities.
- Ferrand, Laura,Tang, Yue,Aubert, Corinne,Fensterbank, Louis,Mouriès-Mansuy, Virginie,Petit, Marc,Amatore, Muriel
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p. 2062 - 2065
(2017/04/28)
-
- Gallium-catalyzed reductive lactonization of γ-keto acids with a hydrosilane
-
Described herein is the GaCl3-catalyzed lactonization of γ-keto carboxylic acids in the presence of PhSiH3 leading to the direct preparation of γ-lactone derivatives. This reducing system showed a relatively wide functional group tolerance.
- Sakai, Norio,Horikawa, Shuhei,Ogiwara, Yohei
-
p. 81763 - 81766
(2016/09/09)
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- Catalytic Carbocation Generation Enabled by the Mesolytic Cleavage of Alkoxyamine Radical Cations
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A new catalytic method is described to access carbocation intermediates via the mesolytic cleavage of alkoxyamine radical cations. In this process, electron transfer between an excited state oxidant and a TEMPO-derived alkoxyamine substrate gives rise to a radical cation with a remarkably weak C?O bond. Spontaneous scission results in the formation of the stable nitroxyl radical TEMPO.as well as a reactive carbocation intermediate that can be intercepted by a wide range of nucleophiles. Notably, this process occurs under neutral conditions and at comparatively mild potentials, enabling catalytic cation generation in the presence of both acid sensitive and easily oxidized nucleophilic partners.
- Zhu, Qilei,Gentry, Emily C.,Knowles, Robert R.
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p. 9969 - 9973
(2016/08/16)
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- Toward Customized Tetrahydropyran Derivatives through Regioselective α-Lithiation and Functionalization of 2-Phenyltetrahydropyran
-
In this contribution, the first direct and efficient functionalization of the preformed 2-phenyltetrahydropyran (2-PhTHP) nucleus by electrophilic interception of the corresponding α-lithiated derivative by employing sBuLi as the base and THF as the solvent at –78 °C was explored. The presence of N,N,N′,N′-tetramethylethylenediamine (TMEDA) proved to be critical to governing reaction feasibility both in polar and apolar solvents and for improving the yield of the reaction. Both carbon- and heteroatom-based halides were found to be competent electrophiles for this transformation, as well as aliphatic and aromatic aldehydes and ketones, isocyanates, and carboxylic acid derivatives. The combination of hexane/TMEDA lowered the rate of racemization of α-lithiated optically active 2-PhTHP, which thereby enabled calculation of its barrier to inversion at –78 °C.
- Cicco, Luciana,Addante, Valeria,Temperini, Andrea,Donau, Carsten Adam,Karaghiosoff, Konstantin,Perna, Filippo Maria,Capriati, Vito
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p. 3157 - 3161
(2016/07/19)
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- Direct C-H bond activation of ethers and successive C-C bond formation with benzene by a bifunctional palladium-titania photocatalyst
-
Palladium-loaded titanium oxide was found to work as a bifunctional photocatalyst for functionalization of benzene with ether upon photoirradiation, without using any special reagents. The metal-loaded TiO2 photocatalyst activated a C-H bond of ethers and the heterogeneous Pd metal nanoparticle catalyst promoted the successive C-C bond formation between benzene and the radical species. In this reaction, benzene reacted very selectively with the α-carbon of various ethers at least in the initial stage of the reaction. Kinetic and ESR studies revealed a detailed mechanism for the reaction.
- Tyagi, Akanksha,Matsumoto, Tomoya,Kato, Tatsuhisa,Yoshida, Hisao
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p. 4577 - 4583
(2016/07/06)
-
- Simple salts of abundant metals (Fe, Bi, and Ti) supported on montmorillonite as efficient and recyclable catalysts for regioselective intramolecular and intermolecular hydroalkoxylation reactions of double bonds and tandem processes
-
The transfer of catalytic hydroalkoxylation reactions of olefins from homogeneous to heterogeneous conditions has been studied using two types of solid catalysts, namely montmorillonite (MMT) doped with metal cations and metal nanoparticles supported on oxides. In the case of intramolecular reactions, 38-99% yields of cyclic ethers have been obtained using Fe-MMT and Bi-MMT both in CH3NO2 and dimethyl carbonate (DMC) compared with other supported metal salts or metal nanoparticles. In the case of more challenging intermolecular reactions, conversions up to 72% and yields up to 54% were obtained with metal-doped MMT as well, such as Fe-, Bi-, and Ti-MMT. In this paper, we detail the substrate scope and limitations for both classes of reactions and tandem processes, their transposition in flow and some mechanistic insights concerning the active species, in processes identified as truly heterogeneously catalysed. As a general trend, it was observed that trisubstituted double bonds allowed the best results both in intra- and intermolecular reactions. The transfer of homogeneous catalysts onto heterogeneous ones in the case of Fe-MMT and Bi-MMT was successful and even allowed enhanced catalytic activities in the case of Bi-MMT.
- Notar Francesco, Irene,Cacciuttolo, Bastien,Pascu, Oana,Aymonier, Cyril,Pucheault, Mathieu,Antoniotti, Sylvain
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p. 19807 - 19818
(2016/03/01)
-
- A combined computational and experimental investigation of the oxidative ring-opening of cyclic ethers by oxoammonium cations
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The propensity of oxoammonium cations to facilitate the oxidative ring-opening of cyclic ethers to their corresponding distal hydroxy ketones is investigated. The reaction has been evaluated using experimental and computational methods to gain deeper insight into trends in reactivity.
- Loman, Jacob. J.,Carnaghan, Emma R.,Hamlin, Trevor A.,Ovian, John M.,Kelly, Christopher B.,Mercadante, Michael A.,Leadbeater, Nicholas E.
-
supporting information
p. 3883 - 3888
(2016/05/24)
-
- Simple metal salts supported on montmorillonite as recyclable catalysts for intramolecular hydroalkoxylation of double bonds in conventional and VOC-exempt solvents
-
We describe herein an efficient and particularly sustainable catalytic system for the intramolecular hydroalkoxylation of double bonds. A heterogeneous catalyst based on the impregnation of benign metals such as iron and bismuth on montmorillonite was used for a highly atom-economic transformation in DMC, a non-VOC solvent. The transformation allowed the formation of a large range of cyclic ethers from the corresponding unsaturated alcohols and the catalyst could be recycled several times.
- Notar Francesco, Irene,Cacciuttolo, Bastien,Pucheault, Mathieu,Antoniotti, Sylvain
-
supporting information
p. 837 - 841
(2015/03/04)
-
- Selective synthesis of unsymmetrical ethers from different alcohols catalyzed by sodium bisulfite
-
An efficient method for the preparation of unsymmetrical ethers from alcohols catalyzed by sodium bisulfite is reported. The procedure enables the direct dehydration of primary, secondary, and tertiary benzylic alcohols with aliphatic alcohols in the abse
- Yu, Jun-Lai,Wang, Hui,Zou, Kai-Feng,Zhang, Jia-Rui,Gao, Xiang,Zhang, Dan-Wei,Li, Zhan-Ting
-
p. 310 - 315
(2013/01/15)
-
- Calcium catalyzed hydroalkoxylation
-
A calcium catalyzed intramolecular hydroalkoxylation reaction is presented, as a transition metal free, inexpensive, and very mild process for the highly atom economic formation of cyclic ethers from γ,δ-unsaturated alcohols. In contrast to most of the previously reported procedures, room temperature conditions are fully sufficient in most cases for a high yielding cycloisomerization in the presence of a combination of 5 mol-% Ca(NTf 2)2 and 5 mol-% Bu4NPF6. Full regioselectivity is observed in all transformations.
- Kena Diba, Anastasie,Begouin, Jeanne-Marie,Niggemann, Meike
-
supporting information
p. 6629 - 6632,4
(2012/12/13)
-
- Calcium catalyzed hydroalkoxylation
-
A calcium catalyzed intramolecular hydroalkoxylation reaction is presented, as a transition metal free, inexpensive, and very mild process for the highly atom economic formation of cyclic ethers from γ,δ-unsaturated alcohols. In contrast to most of the previously reported procedures, room temperature conditions are fully sufficient in most cases for a high yielding cycloisomerization in the presence of a combination of 5 mol-% Ca(NTf 2)2 and 5 mol-% Bu4NPF6. Full regioselectivity is observed in all transformations.
- Kena Diba, Anastasie,Begouin, Jeanne-Marie,Niggemann, Meike
-
supporting information
p. 6629 - 6632
(2013/01/15)
-
- New method for C-H arylation/alkylation at α-position of cyclic aliphatic ethers by iron-oxide mediated reaction
-
We report a new and efficient iron oxide catalyzed cross-coupling reaction between organometallic species such as alkyl/arylmagnesium halides or organolithium species and α-hydrogen bearing cyclic unbranched and branched aliphatic ethers via activation of C(sp3)-H. In the presence of 1 mol% of iron oxide, five and six membered unbranched cyclic ethers such as tetrahydrofuran and tetrahydropyran gave good to excellent yields of cross-coupled products. Whereas, in case of branched ether such as 2-methyltetrahydrofuran, it was observed that the arylation occurred at both the sides and gave moderate yields of a mixture of regioisomers. Among the organometallic species used, alkyl organometallic reagents gave less yields as compared to aryl organometallics.
- Singh, Parvinder Pal,Gudup, Satish,Aruri, Hariprasad,Singh, Umed,Ambala, Srinivas,Yadav, Mahipal,Sawant, Sanghapal D.,Vishwakarma, Ram A.
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experimental part
p. 1587 - 1597
(2012/03/22)
-
- Green chemistry: Solvent- and metal-free Prins cyclization. Application to sequential reactions
-
Prins cyclization between a homoallylic alcohol and an aldehyde, promoted by trimethylsilyl halide, afforded 4-halo-tetrahydropyrans with good to excellent yields. Thanks to the absence of the solvent and metal, the THP thus obtained have been implicated
- Clarisse, Damien,Pelotier, Beatrice,Piva, Olivier,Fache, Fabienne
-
supporting information; experimental part
p. 157 - 159
(2012/01/06)
-
- Gold-catalysed cyclic ether formation from diols
-
Gold(I) and (III) salts have been found to be highly effective at the catalysis of ether formation from alcohols. Intramolecular ether formation of a 1,5-diol was also achieved, with a stereoselectivity that indicates that an SN1 mechanism predominates. In an attempt to form a seven-membered ring, a stable 14-membered dimer product was also formed. Attempts to control the diastereoselectivity of the reaction using a chiral anionic counterion did not give products with a high de.
- Jiang, Xiaolu,London, Emma K.,Morris, David J.,Clarkson, Guy J.,Wills, Martin
-
experimental part
p. 9828 - 9834
(2011/02/23)
-
- Direct metalation of methoxymethyl arylmethyl ethers: A tin-free approach to the generation of α-alkoxyalkoxy-substituted aryllithiums
-
The generation of a series of α-methoxymethoxy-substituted arylmethyllithiums was achieved by direct metalation of the corresponding arylmethyl methoxymethyl ethers. While the effect of substituents at the benzylic position is straightforward, substituent
- Azzena, Ugo,Pisano, Luisa,Mocci, Sarah
-
experimental part
p. 3619 - 3625
(2010/01/18)
-
- Gold-catalyzed substitution reaction with ortho-alkynylbenzoic acid alkyl ester as an efficient alkylating agent
-
ortho-Alkynylbenzoic acid alkyl esters behave as alkylating agents in combination with gold catalysts. The reaction with alcohols occurs smoothly in the presence of catalytic amounts of Ph3PAuCl and AgOTf under mild conditions to produce the corresponding ether products in high yields. The protocol is also useful for Friedel-Crafts alkylation and N-alkylation of sulfonamides. The reaction likely proceeds through the gold-induced in situ construction of leaving groups and subsequent nucleophilic attack of nucleophiles, such as alcohols, aromatic compounds, and sulfonamides.
- Aikawa, Haruo,Tago, Sakie,Umetsu, Kazuteru,Haginiwa, Naomichi,Asao, Naoki
-
experimental part
p. 1774 - 1784
(2009/06/20)
-
- Gold-catalyzed etherification and friedel - Crafts alkylation using ortho-alkynylbenzoic acid alkyl ester as an efficient alkylating agent
-
A gold-catalyzed alkylation of alcohols and aromatic compounds is described. The reaction of ortho-alkynylbenzoic acid alkyl esters with alcohols or aromatic compounds occurs in the presence of catalytic amounts of Ph 3PAuCl and AgOTf under mild conditions to produce corresponding ethers or Friedel-Crafts alkylation products in good to high yields. The reaction likely proceeds through the gold-induced in situ construction of leaving groups and subsequent nucleophilic attack of alcohols or aromatic compounds.
- Asao, Naoki,Aikawa, Haruo,Tago, Sakie,Umetsu, Kazuteru
-
p. 4299 - 4302
(2008/02/12)
-
- I2-mediated photochemical preparation of 2-substituted 1,3-dioxolanes and tetrahydrofurans from alcohols with polymer-supported hypervalent iodine reagent, PSDIB
-
Various 2-substituted 1,3-dioxolanes, 1,3-dioxanes, and tetrahydrofurans were obtained selectively in good to moderate yields from the corresponding alcohols with PSDIB in the presence of iodine under irradiation conditions. Moreover, PSDIB was repeatedly used for the same reactions keeping good yield of the cyclic product.
- Teduka, Tomomasa,Togo, Hideo
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p. 923 - 926
(2007/10/03)
-
- Efficient catalytic procedure for etherification of alcohols with MeAl(NTf2)2
-
Efficient catalytic etherification of benzyl and allylic alcohols has been accomplished by use of in situ prepared MeAl(NTf2)2 as a catalyst. The new method was also found to be effective for the selective benzylation of allylic alcohols.
- Ooi, Takashi,Ichikawa, Hayato,Itagaki, Yoshifumi,Maruoka, Keiji
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p. 575 - 578
(2007/10/03)
-
- A new generation of alkoxyl radical precursors - Preparation and properties of N-(alkoxy)-4-arylthiazole-2(3H)-thiones
-
N-(Hydroxy)thiazole-2(3H)-thiones 6-10 have been prepared in a short and efficient synthesis from p-substituted acetophenones. Alkylation of heterocycles 6-10 in the form of their potassium or tetraalkylammonium salts 11-15 affords N-alkoxy-4-arylthiazole-2(3H)-thiones 16-20 in good to satisfactory yields. The hitherto unknown thiones 16-20 have been subjected to a detailed structural investigation (NMR spectroscopy and X-ray crystallography) and furthermore to a mechanistic study in order to explore their utility as sources of oxygen-centered radicals in solution. From the results of these studies, the following conclusions can be drawn: (i) X-ray analyses of the p-chlorophenyl-substituted acid 9, of the O-alkyl derivatives 19c, 19f, and of the O-mixed anhydride 19k indicate short C-S bonds [C2-S2 = 1.637(5)-1.684(2) A] and long N-O connectivities [N3-O1 = 1.369(3)-1.379(2) A] in the thiohydroxamate functionalities. Furthermore, O-alkyl- or O-acyl substituents at O1 are twisted out of the thiazolethione plane by ca. 90°, which points to lone-pair repulsion between nitrogen and oxygen atom as the underlying structural motif of the cyclic thiohydroxamate derivatives. (ii) Alkylation of ambidentate thiohydroxamate anions (salts 11-15; oxygen and sulfur nucleophiles) affords almost exclusively O-esters 16-20 (alkylation at the oxygen atom). (iii) Based on the results of X-ray diffraction studies and on the 1H- and 13C-NMR spectra, guidelines for the characterization of N- (alkoxy)thiazolethiones 16-20 and 2-(alkylsulfanyl)thiazole N-oxides 21-25, i.e. the products of S-alkylation of thiohydroxamate salts 11-15, could be derived. (iv) Photolyses of substituted N-(4-pentenoxy)-4-arylthiazolethiones 16-20 in general and in particular of p-chloro derivatives 19 were carried out in the presence of the hydrogen donor Bu3SnH, and afforded substituted tetrahydrofurans 31 or tetrahydropyrans 32 as major products in good yields. The observed stereo- and regioselectivities of ethers 31 and 32 point to alkoxyl radicals 30 as reactive intermediates, which add intramolecularly by selective 5-exo-trig or 6-endo-trig pathways to the olefinic double bonds. In terms of synthetic access and ease of handling of the radical precursors, the p-chlorophenyl-substituted thiazolethiones 9 and 10 exhibit significant advantages over all the other thiones used in this study and are considered as excellent substitutes for the pyridinethiones as efficient sources of free alkoxyl radicals. Consequently, the present compounds may be of use in both mechanistic and synthetic studies.
- Hartung, Jens,Schwarz, Michaela,Svoboda, Ingrid,Fuess, Hartmut,Duarte, Maria Teresa
-
p. 1275 - 1290
(2007/10/03)
-
- An efficient and stereoselective conversion of lactones to substituted cyclic ethers
-
A general route to substituted cyclic ethers has been described by using nucleophilic addition of Grignard reagents to lactones in the presence of CeCl3 followed by the Lewis acid-induced deoxygenation of the corresponding hemiketals with Et3SiH. Stereoselective reduction of the 5-membered adducts to the disubstituted tetrahydrofurans has been also investigated.
- Yoda, Hidemi,Mizutani, Masato,Takabe, Kunihiko
-
p. 679 - 686
(2007/10/03)
-
- Controlling factors determining the regiochemistry of intramolecular alkoxymercuration
-
The intramolecular alkoxymercuration of (E)-5-arylpent-4-en-1-ols indicated that the regioselectivity is closely related to the Hammett constants of the para-substituents on the benzene ring. Large solvent effects on the regioselectivity were also observe
- Senda, Yasuhisa,Kanto, Hiroko,Itoh, Hiroki
-
p. 1143 - 1146
(2007/10/03)
-
- Towards Improved Alkoxyl Radical Precursors - The Synthesis of N-Alkoxy-4-(p-chlorophenyl)thiazole-2(3H)-thiones
-
4-(p-Chlorophenyl)-3-hydroxythiazol-2(3H)-thione (3) can be prepared in good yields and in useful quantities from p-chloro acetophenone (1). O-Alkylation of the cyclic thiohydroxamic acid 3 via the respective potassium or the tetraethyl ammonium salts affords the esters 4. A slightly modified procedure allows the conversion of the acid 3 to the mixed anhydrides 5. The esters 4 and the anhydrides 5 are colorless to yellowish crystalline compounds which show a good shelf life. Visible light photolysis of the N-alkoxy derivatives 4e-g and reactive hydrogen donors affords substituted tetrahydrofurans 7 or tetrahydropyrans 8 via an alkoxyl radical pathway.
- Hartung, Jens,Schwarz, Michaela
-
p. 848 - 850
(2007/10/03)
-
- Photoreactions of Phenyl-Substituted N-(Pent-4-enyl-1-oxy)pyridine-1(1H)-thiones
-
A series of hitherto unknown N-(pent-4-enyl-1-oxy)pyridine-2(1H)-thiones (6) were prepared from substituted pent-4-enyl tosylates or benzylic chlorides.On irradiation with incandescent light heterocycles 6 liberated alkoxy radicals 2, which were studied for rearrangement reactions.Surprisingly, all transformations involving the 1-phenylpent-4-enyl-1-oxy radical (2a), for example, to give the substituted thioether 8, 2-bromomethyl-5-phenyltetrahydrofuran (11), or the tetrahydrofuran 14a, were not stereoselective.On the other hand 2-, 3-mono-, and 1,5-disubstituted pent-4-enyl-1-oxy radicals 2d-e and 2g cyclized in good yields and with good to excellent stereoselectivities to give the corresponding 2,4-cis- and 2,3-trans-phenyltetrahydrofurfuryl radicals 3d-e, and the trans-2-benzyl-5-methyl substituted intermediate 3g.The major reaction mode of the 4-phenylpent-4-enyl-1-oxy radical (2f) was the 6-endo cyclization, which afforded 3-phenyltetrahydropyran (13f) as the major product (endo:exo=93:7) after trapping with hydrogen donors.According to the experimental data of the present study, the unusual reactivity of the 1-phenylpent-4-enyl-1-oxy radical (2a) in 5-exo-trig ring closures could be caused by a coplanar arrangement of the benzyloxy moiety in the transition state of the cyclization.This interaction would lock the radical center in 2a in a preferred conformation, which would result in similar steric effects for both cis- and trans-cyclizations. - Keywords: alkoxy radicals; cyclizations; pyridinethiones; radicals; tetrahydrofurans
- Hartung, Jens,Hiller, Margit,Schmidt, Philipp
-
p. 1014 - 1023
(2007/10/03)
-
- Formation of heterocycles by the Mitsunobu reaction. Stereoselective ynthesis of (+)-α-skytanthine
-
Cyanomethylenetributylphosphorane was shown to mediate the dehydrocyclization of diols and amino alcohols to give the corresponding 6-membered O- and N-heterocycles in 90% or better yields. Using the reaction as a key step, (+)-α-skytanthine, a unique mono terpene alkaloid, was synthesized stereoselectively.
- Tsunoda,Ozaki,Shirakata,Tamaoka,Yamamoto,Ito
-
p. 2463 - 2466
(2007/10/03)
-
- Mitsunobu-type alkylation of p-toluenesulfonamide. A convenient new route to primary and secondary amines
-
p-Toluenesulfonamide, which is known to form phosphine imides under Mitsunobu conditions, was shown to be alkylated in the presence of cyanomethylenetributylphosphorane to give N-substituted sulfonamides in excellent yields. The reaction can be applied to the synthesis of symmetrical and unsymmetrical N,N-disubstituted amides. When coupled with the desulfurization reactions, the reaction provides a new versatile synthetic route to primary and secondary amines from ammonia.
- Tsunoda, Tetsuto,Yamamoto, Hidetoshi,Goda, Kayo,Ito, Sho
-
p. 2457 - 2458
(2007/10/03)
-
- Stereoselective Syntheses of α-Substituted Cyclic Ethers and syn-1,3-Diols
-
In the presence of a catalytic amount of triphenylmethylium hexachloroantimonate or a catalyst system of antimony pentachloride, chlorotrimethylsilane and tin(II)iodide, α-substituted cyclic ethers are stereoselectively prepared from lactones by successiv
- Homma, Koichi,Takenoshita, Haruhiro,Mukaiyama, Teruaki
-
p. 1898 - 1915
(2007/10/02)
-
- Addition of Benzotriazole to Vinyl Ethers. Chemistry of the Adducts
-
Benzotriazole adds readily to ethyl vinyl ether, to 2,3-dihydrofuran, and to 3,4-dihydro-2H-pyran to form the respective α-benzotriazolyl ethers.Reactions of benzotriazole with α-methoxy derivatives of tetrahydrofuran and tetrahydropyran give similar products by substitution of benzotriazolyl for the methoxy groups.The corresponding adducts of benzotriazole and vinyl acetates are unstable and eliminate acetate anion to form geminal bis(benzotriazolyl)alkanes.The products show benzotriazol-1-yl to -2-yl isomerization. α-Benzotriazolyl derivatives of tetrahydrofuran and tetrahydropyran react with phenyl- and alkynyl-magnesium reagents to give the respective α-phenyl or α-alkynyl cycloethers.Alkylmagnesium halides by contrast attack the benzotriazolyl N-3 atom of these adducts and open the tetrahydropyranyl ring with formation of an N,N'-disubstituted o-phenylenediamine. 1H and 13C NMR spectra of the products are discussed.
- Katritzky, Alan R.,Rachwal, Stanislaw,Rachwal, Bogumila
-
p. 1717 - 1725
(2007/10/02)
-
- A CONVENIENT SYNTHESIS OF CYCLIC ETHERS FROM SILOXY CARBONYL COMPOUNDS
-
Five-seven membered cyclic ethers are prepared by one-pot procedure in good yields from γ-, δ-, and ε-siloxy carbonyl compounds, respectively, on treatment with silyl nucleophiles (triethylsilane, allyltrimethylsilane, trimethylsilyl cyanide, etc.) in the
- Homma, Koichi,Mukaiyama, Teruaki
-
p. 259 - 262
(2007/10/02)
-
- SUBSTITUTION REACTIONS OF 2-BENZENESULPHONYL CYCLIC ETHERS WITH CARBON NUCLEOPHILES
-
Direct substitution of 2-benzenesulphonylcyclic ethers was studied using a variety of carbon nucleophiles.These nucleophiles included organozinc reagents (derived from aryl, vinyl and alkynyl Grignard reagents) or silyl enol ethers, silyl ketene acetals,
- Brown, Dearg S.,Bruno, Maurizio,Davenport, Raymond J.,Ley, Steven V.
-
p. 4293 - 4308
(2007/10/02)
-
- DIRECT SUBSTITUTION OF 2-BENZENESULPHONYL CYCLIC ETHERS USING ORGANOZINC REAGENTS
-
2-Benzenesulphonyl cycle ethers are converted in good yield at room temperature to the 2-aryl-, 2-alkenyl or 2-alkynyl product by treatment with the corresponding organozinc species.
- Brown, Dearg S.,Ley, Steven V.
-
p. 4869 - 4872
(2007/10/02)
-
- Reaction of Acetals with Grignard Reagents
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The reaction of dialkyl acetals derived from α,β-unsaturated aldehydes with Grignard reagents using TiCl4 in THF afforded the cross coupling products, allyl ethers, in high yields.The TiCl4-promoted reaction of alkyl 2,4-dichlorophenyl acetals, synthesized from 3,4-dihydro-2H-pyran or ethyl vinyl ether and 2,4-dichlorophenol, with Grignard reagents in THF at low temperature afforded the corresponding unsymmetrical ethers in high yields.When alkyl 2,4-dichlorophenyl acetals, synthesized from aromatic aldehyde or vinyl ethers and 2,4-dichlorophenol, were treated with Grignard reagents in benzene or toluene at room temperature in the absence of TiCl4, the cross coupling reaction took place and the corresponding ethers were isolated in good yields.
- Ishikawa, Hiroshi,Mukaiyama, Teruaki,Ikeda, Shigeru
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p. 776 - 780
(2007/10/02)
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