18417-40-8Relevant articles and documents
1,3-Cycloaddition of nitrile oxides in ionic liquids. An easier route to 3-carboxy isoxazolines, potential constrained glutamic acid analogues
Conti, Dario,Rodriquez, Manuela,Sega, Alessandro,Taddei, Maurizio
, p. 5327 - 5330 (2003)
Several improvements in the cycloaddition of carboethoxyformonitrile oxide (CEFNO) with different alkenes are observed in the ionic liquids [bmim][BF4] and [bmim][PF6]. The possibility of obtaining good yields of the corresponding is
Synthesis of α-Nitro Carbonyls via Nitrations in Flow
Chentsova, Anna,Ushakov, Dmitry B.,Seeberger, Peter H.,Gilmore, Kerry
, p. 9415 - 9421 (2016/10/17)
Reported is a safe, rapid method for the synthesis of α-nitro esters via the trapping of nitronium ions. The two-stage nitration and subsequent deacetylation of readily available 1,3-dicarbonyl compounds was achieved using a biphasic semicontinuous approach. α-Nitro esters and amides were obtained in good overall yields (53-84%). Some of the α-nitro-1,3-dicarbonyl intermediates exhibit enhanced reactivity and undergo an acid-catalyzed Nef-type reaction to α-oxo-carbonyls.
Three-component coupling approach to trachyspic acid
Schmitt, Daniel C.,Lam, Leighann,Johnson, Jeffrey S.
supporting information; experimental part, p. 5136 - 5139 (2011/11/29)
Three-component coupling of the lithium enolate of t-BuOAc, silyl glyoxylate, and an α,β-unsaturated ketone enables the rapid construction of the trachyspic acid carbon skeleton. A 3,4-disubstituted isoxazole is utilized to mask the C7/C9 dicarbonyl. New
Friedel-Crafts-type reactions involving di- and tricationic species. Onium-allyl dications and O,O-diprotonated aci-nitro species bearing a protonated carbonyl group
Ohwada, Tomohiko,Yamagata, Naoko,Shudo, Koichi
, p. 1364 - 1373 (2007/10/02)
Stable carbocations do not react with nonactivated benzenes. For example, acetophenone does not react with benzene in the presence of trifluoromethanesulfonic acid (TFSA), while trifluoroacetophenone does do so under acidic conditions owing to activation of the electrophilicity of the hydroxycarbenium cation by the trifluoromethyl group. This and other studies suggest that an electron-withdrawing substituent on the cationic center increases the reactivity toward benzenes. In this paper, involvement of multiply positively charged (dicationic and tricationic) species, which have sufficient electrophilicity toward benzene, is demonstrated in the acid-catalyzed reactions of cinnamaldehyde and its derivatives and also in the acid-catalyzed reactions of nitromethanes. The species formed from cinnamaldehyde, cinnamaldimine, cinnamaldoxime, and their derivatives in TFSA or TFSA-SbF5 have an adequate reactivity toward benzene. O-Protonated cinnamaldehyde and its derivatives, N-protonated cinnamaldimine, and N,N-dimethylcinnamaldiminium salt do not react with benzene. Since a strong acid catalyst is required for the reactions, participation of doubly protonated species, onium-allyl dications, is proposed. Ab initio calculations of (1) the donor-acceptor interaction energies of a neutral donor (such as water and ammonia) and a doubly charged allyl dication and (2) proton affinities demonstrated that the ammonium-allyl dication is more stable than the oxonium-allyl dication, in accordance with the experimental observation. Nitronic acids also react with benzene at the ipso position with respect to the nitro group to give the phenylated oximes in the presence of TFSA. The reaction with benzene is not catalyzed by trifluoroacetic acid, which is sufficiently acidic to monoprotonate a nitronic acid to the protonated aci-nitro form. The reaction requires a stronger acid, trifluoromethanesulfonic acid, suggesting intervention of the dication formed by O,O-diprotonation of acinitroalkanes rather than the monoprotonated aci-nitroalkane. As a result of further study on the phenylation reactions, we found a facile phenylation reaction of nitromethanes substituted with an electron-withdrawing group, catalyzed by TFSA, to give phenylated α-carbonyloximes in high yields. A triply positively charged cation, an O,O-diprotonated aci-nitro species bearing a protonated ethoxycarbonyl group, which can react with nonactivated benzene, is proposed to be an intermediate in this reaction.
Cycloaddition of nitrile oxides to 3-O-benzyl-5,6-dideoxy-1,2-O-isopropylidene-α-D-ribo-hex-5-enofuranose
Blake, Alexander J.,Gould, Robert O.,McGhie, Karen E.,Paton, R. Michael,Reed, David,et al.
, p. 461 - 474 (2007/10/02)
Benzonitrile oxide and ethoxycarbonylformonitrile oxide cyclo-added to the title compound to afford a mixture of 3-substituted (phenyl or ethoxycarbonyl)(5R)- (6) and (5S)-5-(3-O-benzyl-1,2-O-isopropylidene-α-D-ribo-tetrofuranos-4-yl)-2-isoxazoline (7).Th
Hydroxynitrilium ions as intermediates in the reaction of nitroderivatives with aromatics
Coustard, Jean-Marie,Jacquesy, Jean Claude,Violeau, Bruno
, p. 3075 - 3078 (2007/10/02)
In acids reaction of ethyl nitroacetate 1 and of a nitroacetophenone 14 with aromatics yields E oximes 2 and 15, respectively, addition occurring on the corresponding hydroxynitrilium ion.
