- Conformational properties of trans-2-halo-acetoxycyclohexanes: 1H NMR, solvation and theoretical investigation
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Conformational analyses of trans-2-halo-acetoxycyclohexanes have been performed through NMR, theoretical calculations and solvation theory. The solvent dependence of coupling constants analysed together with solvation parameters of the main calculated geo
- Freitas, Matheus P.,Tormena, Cláudio F.,Rittner, Roberto,Abraham, Raymond J.
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- Intermolecular Halogenation/Esterification of Alkenes with N-Halosuccinimide and Acetic Acid Catalyzed by 1,4-Diazabicyclo[2.2.2]octane
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1,4-Diazabicyclo[2.2.2]octane (DABCO) is a suitable Lewis base that acts as an organocatalyst in the activation of N-chlorosuccinimide (NCS) towards the chlorination of alkenes. The chloriranium ion formed from NCS and the alkene, can be intermolecularly opened by a nucleophile, such as acetic acid, to produce highly functionalized trans-chloro esters in high yields. The protocol is also applied to the synthesis of chlorohydrins and chloro ethers using water or methanol as nucleophiles instead of acetic acid. Brominated analogs can also be synthesized from alkenes and N-bromosuccinimide (NBS) in the presence of various basic catalysts. However, the reaction patterns seem to be remarkably different. The catalytic performance of bases in the bromoesterification of alkenes was found to be strongly affected by their Br?nsted basicity, suggesting that acetyl hypobromite, formed in situ from NBS and acetic acid, acts as a real brominating agent in these systems. (Figure presented.).
- Pimenta, Laura S.,Gusevskaya, Elena V.,Alberto, Eduardo E.
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supporting information
p. 2297 - 2303
(2017/07/07)
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- Phase-transfer and other types of catalysis with cyclopropenium ions
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Abstract This work establishes the cyclopropenium ion as a viable platform for efficient phase-transfer catalysis of a diverse range of organic transformations. The amenability of these catalysts to large-scale synthesis and structural modification is demonstrated. Evaluation of the molecular structure of an optimal catalyst reveals some unique structural features of these systems. Finally, a discussion of electronic charge distribution underscores an important consideration for catalyst design. Aromatic ions: Tris(dialkylamino)cyclopropenium ions are shown to be effective carbocationic phase-transfer catalysts for a variety of mainstay transformations. The cyclopropenium platform is shown to be modular and accessible on scale. An X-ray structure and electron-density map revealed some unique features of this architecture (see scheme).
- Bandar, Jeffrey S.,Tanaset, Anont,Lambert, Tristan H.
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supporting information
p. 7365 - 7368
(2015/05/13)
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- Enzymatic preparation of (1S,2R)- and (1R,2S)-stereoisomers of 2-halocycloalkanols
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The stereoisomers of cis-2-halocycloalkanols were resolved by a kinetically controlled transesterification with vinyl acetate in the presence of lipases in organic media. High enantioselectivities (ee >98%) and good isolated yields were obtained for all substrates using the appropriate lipase. Burkholderia cepacia lipase was the most efficient enzyme for the resolution of these substrates. The enantiomeric purities of the compounds were defined by derivatization with Mosher's acid and the absolute configurations were determined by chemical correlation.
- Kolodiazhna, Olga O.,Kolodiazhna, Anastasy O.,Kolodiazhnyi, Oleg I.
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- Convenient synthesis of chlorohydrins from epoxides using zinc oxide: Application to 5,6-epoxysitosterol
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Efficient synthesis of protected and unprotected chlorohydrins has been achieved by ring opening of epoxides with acetyl/benzoyl chloride and TMSCl using a catalytic amount of ZnO as a reusable catalyst. The applicability of ZnO is further extended by performing the cleavage of the natural product 5,6-epoxysitosterol with acetyl chloride.
- Moghaddam, Firouz Matloubi,Saeidian, Hamdollah,Mirjafary, Zohreh,Javan, Marjan Jebeli,Farimani, Mehdi Moridi,Seirafi, Marjan
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experimental part
p. 157 - 163
(2009/09/30)
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- Trichloroisocyanuric Acid as a Cohalogenating Reagent: An Efficient Transformation of Alkenes into Chlorohydrins, β-Chloroethers and β-Chloroacetates
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The preparation of diverse β-chloroethers, β-chloroacetates, and chlorohydrins is efficiently achieved under mild conditions by reaction of alkenes with trichloroisocyanuric acid (0.34 mol equiv) in alcohols (MeOH, EtOH, i-PrOH, t-BuOH), acetic acid or aqueous acetone, respectively.
- Mendonca, Gabriela Fonseca,Sanseverino, Antonio Manzolillo,Mattos, Marcio C. S. de
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- A one-pot synthesis of β-chloro acetates/benzoates from epoxides
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A variety of epoxides were converted into β-chloroacetates and benzoates by using TMSCI and the corresponding acid anhydride in the presence of a catalytic amount of Cu(OTf)2.
- Chandra, Kusum L.,Bisai, Alakesh,Saravanan,Singh, Vinod K.
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p. 221 - 223
(2007/10/03)
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- Addition reactions of nitryl chloride at multiple bonds
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Published data on additio of nitryl chloride to alkenes and possible reaction mechanisms were analyzed. Reactions of nitryl chloride with alkenes differing in the ionization potentials of the double bond and in the abilities to undergo various structural rearrangements were studied. Nitryl chloride was shown to be very sensitive both to the substrate and to the reaction conditions.
- Zyk,Bondarenko,Nesterov,Zefirov
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p. 980 - 986
(2007/10/03)
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- Organomercury/aluminum-mediated acylative cleavage of cyclic ethers
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Epoxides and tetrahydrofurans are cleaved with concomitant acylation to chloroalkyl esters using a reagent system composed of an organomercurial, aluminum metal and an acid chloride. The cleavage is promoted under mild conditions by a range of readily-available cyclic β-alkoxychloromercurials and acid chlorides. Using mainly tetrahydrofuran and cyclohexene oxide as substrates, the yield of isolated chloroesters ranged from 52 to 96%.
- Luzzio, Frederick A.,Bobb, Rhiana A.
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p. 1851 - 1858
(2007/10/03)
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- Efficient and Regioselective Conversion of Epoxides into Vicinal Chloroesters with TiCl4 and Imidazole in Ethyl Acetate
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Epoxides can be cleaved easily in EtOAc with TiCl4 in the presence of imidazole to afford β-chloroesters with excellent yields and regioselectivity.
- Iranpoor,Zeynizadeh
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p. 582 - 583
(2007/10/03)
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- Lanthanoid-catalyzed ring-opening reaction of epoxides with acyl halides
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Eu(dpm)3 [dpm: dipivaloylmethanate] catalyzes the ring-opening reaction of epoxides with acyl halides affording the corresponding 2-haloalkyl esters. The stereochemical course was confirmed as trans-addition in the case of the reaction of cyclo
- Taniguchi, Yuki,Tanaka, Shintaro,Kitamura, Tsugio,Fujiwara, Yuzo
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p. 4559 - 4560
(2007/10/03)
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- Synthesis of an enantiomerically pure aminoisoquinocarbazole with antiarrhythmic activity via lipase-catalyzed enantioselective transesterification
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Enantiomerically pure (R)-2-cyclohexen-1-ol 5 was prepared via lipase- catalyzed enantioselective transesterification of 2-substituted cyclohexanol, and stereospecifically converted to (-)-(2-cyclohexenyl)acetic acid 4. Enantiomerically pure aminoisoquinocarbazole 1 (RS-2135) was synthesized stereoselectively from 4, using an intramolecular Diels-Alder reaction and Curtius rearrangement.
- Fukazawa, Tetuya,Shimoji, Yasuo,Hashimoto, Toshihiko
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p. 1649 - 1658
(2007/10/03)
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- Yttrium compounds: New catalysts for the regioselective acylative cleavage of epoxides
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The use of Cp2YCl and YCl3 as effective catalysts for the regioselective acylative cleavage of epoxides, especially for the conversion of α,β- epoxyketones to α-chloroenones is described.
- Qian,Zhu
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p. 2203 - 2214
(2007/10/02)
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- Synthesis of enantiomerically pure (R)-2-cycloalken-1-ols using highly enantioselective enzymatic transesterification
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Optically pure (R)-2-cycloalken-1-ols were synthesized via highly enantioselective lipase-catalyzed transesterification of 2-substituted cycloalkanols.
- Fukazawa,Hashimoto
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p. 2323 - 2326
(2007/10/02)
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- Cobalt(II)chloride catalysed cleavage of ethers with acyl halides: Scope and mechanism
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Cobalt(II) chloride in acetonitrile catalyses the cleavage of a wide variety of ethers with acyl halides under mild conditions to give the corresponding esters in good yields. Acyclic aliphatic ethers are cleaved to the corresponding ester and chlorides whereas the cyclic aliphatic ethers give rise to the ω-chloroesters. The benzyl ethers can be converted to the corresponding esters along with the formation of benzyl chloride and benzyl acetamide. A comparative study for the cleavage of allyl and benzyl ether has revealed that benzyl ether can be selectively cleaved in presence of the allyl ethers. The oxiranes can be cleaved in highly regioselective manner to the corresponding-β-chloroesters. The vinyl ethers undergo sp2-hybridised carbon-oxygen bond cleavage under these conditions. Based on product analysis, a mechanism involving electron transfer followed by O-acylation and S(N)1 or S(N)2 attack by chloride-ion is discussed.
- Iqbal,Srivastava
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p. 3155 - 3170
(2007/10/02)
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- OXIDATIVE ADDITION OF ANIONS TO ALKENES BY THE ACTION OF COMPOUNDS OF TETRAVALENT LEAD IN THE PRESENCE OF CHLORIDE ION IN AN ACIDIC MEDIUM
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In the reaction of alkenes (cyclohexene, 1-hexene, styrene) with compounds of tetravalent lead in various acids (trifluoroacetic, acetic, methanesulfonic, perchloric) in the presence of metal chlorides the joint addition of the chloride anion and the anion of the respective acids to the alkenes takes place with a high degree of selectivity, leading to the formation of vicinal bifunctional derivatives of alkanes.The effectiveness of the addition of the anions of the acids to the alkenes under the given conditions varies directly with the strength of the acid and inversely with the nucleophilicity and the basicity of its anion.A new convenient method is proposed for the oxidative chlorofluorination of cyclohexene in aqueous hydrofluoric acid.
- Serguchev, Yu. A.,Gutsulyak, R. B.
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p. 1784 - 1790
(2007/10/02)
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- DOMINANT cis-DIACETOXYLATION OF ALKENES WITH TELLURIUM(IV) OXIDE AND LITHIUM BROMIDE IN ACETIC ACID
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Oxidation of alkenes with tellurium(IV) oxide and lithium bromide in acetic acid affords the corresponding α,β-diacetoxyalkanes in good yields after acetylation of the primary products with acetic anhydride/pyridine.From cyclic alkenes such as cyclopentene, cyclohexene, cycloheptene, and 1,4-cyclohexadiene, the cis-diacetate is obtained as almost the sole product.In the cases of linear cis alkenes such as cis-2-octene and cis-4-octene cis-stereochemistry is also preferred (cis/trans = 87-89/13-11), while the proportion of the cis-product is decreased in the cases of the corresponding trans-alkenes (cis/trans = 56-58/44-42).Transformation of a C-Te bond to a C-OAc bond under these reaction conditions is shown unambiguously by using β-chloroalkyltellurium(IV) trichlorides (TeCl4 adducts of alkenes) and β-oxyalkyl phenyl tellurides (oxytellurenylation products of alkenes), cis-diacetates being solely formed from the trans-tellurium compounds in a cyclohexyl system.One of the possible reaction patways for the oxidation is proposed which involves the acetoxy-, hydroxy-, and/or halogeno-tellurinylation of a double bond followed by an SN2 type acetolysis of the produced C-Te bond.
- Uemura, Sakae,Ohe, Kouichi,Fukuzawa, Shin-Ichi,Patil, Suresh R.,Sugita, Nobuyuki
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- CIS 1,2-FUNCTIONALIZATION OF CYCLOHEXANE USING SELENIUM INTERMEDIATES
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The trans 1,2-phenylseleno acetate, acetamide, alcohol and nitrile of cyclohexane may be oxidized at selenium by halogens and the phenylseleno moiety displaced by halide to give high yields of 1,2 halide-containing products with cis geometry.
- Morella, Angelo M.,Ward, A. David
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p. 2899 - 2900
(2007/10/02)
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- PARTICIPATION OF SULFONATE IONS IN THE ELECTROPHILIC ADDITION OF HALOGENS TO OLEFINS
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The reactions of ethylene, 1-heptene, cyclohexene, and styrene with chlorine and bromine in methylene chloride and chloroform in the presence of tetrabutylammonium p-toluenesulfonate and tetrabutylammonium methanesulfonate were investigated.In all cases the 2-halogenoalkyl esters of the sulfonic acids were obtained with comparable yields in addition to the 1,2-dihalides.The addition of chlorine and bromine to cyclohexene and also of bromine to 1-heptene in acetic acid in the presence of lithium p-nitrobenzenesulfonate leads to 2-halogenoalkyl esters of the sulfonicacids and acetic acid in addition to the 1,2-dihalides.These data indicate concurrent combination of the sulfonate anions at the concluding stage of AdE reactions.The mechanistic aspects and consequences of this effect are discussed.
- Zefirov, N. S.,Koz'min, A. S.,Dan'kov, Yu. V.,Zhdankin, V. V.,Kirin, V. N.
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p. 205 - 213
(2007/10/02)
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- LEAD(IV)ACETATE-METAL HALIDE REAGENTS II. A NEW METHOD FOR THE SYNTHESIS OF β-HALO CARBOXYLATES AND β-IODO ETHERS
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A new method for the synthesis of trans-β-halo carboxylates and trans-β-iodo ethers from alkenes using lead(IV)acetate-metal halide is described.KEYWORDS - lead(IV)acetate; metal halide; alkene; trans-β-halo carboxylate; trans-β-iodo ether
- Motohashi, Shigeyasu,Satomi, Masakichi,Fujimoto, Yasuo,Tatsuno, Takashi
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p. 1788 - 1791
(2007/10/02)
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- Reactions du n=chloroparatoluenesulfonamidate de sodium (chloramine t) sur les olefines en miliu acide organique
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Vic. chloro-acetoxy and vic. chloro-tosylamino alcanes are the main products of the electrophilic reaction of chloramine T on olefins in acetic acid. The stereochemistry of the acetoxy chloration of the 2-butenes and cyclohexene is trans.
- Damin, Bernard,Garapon, Jacques,Sillion, Bernard
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p. 1709 - 1710
(2007/10/02)
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