- Chemoselective, Isomerization-Free Synthesis of N-Acylketimines from N–H Imines
-
N-Acylketimines were synthesized through a ruthenium-catalyzed generation of N–H ketimines from secondary azides and subsequent acylation with mixed anhydrides under mild conditions. The synthetic scope was broad to give N-acylimines having various functi
- Kwon, Yearang,Rhee, Young Ho,Park, Jaiwook
-
supporting information
p. 1503 - 1507
(2017/05/05)
-
- B(C6F5)3-catalyzed synthesis of benzylic azides
-
B(C6F5)3 was found to catalyze the reaction between trimethylsilyl azide and benzylic acetates. Secondary and tertiary benzylic acetates were competent substrates in this reaction providing the azide products in moderate t
- Wrigley, Michael S.,Barker, Timothy J.
-
p. 1771 - 1776
(2017/09/23)
-
- A concise synthesis of quinolinium, and biquinolinium salts and biquinolines from benzylic azides and alkenes promoted by copper(II) species
-
A novel copper-promoted multiple aza-[4 + 2] cycloaddition reaction of N-methyleneanilines in situ generated from benzylic azide and alkenes afforded quinolinium salts, biquinolinium salts, biquinolines or substituted quinolines depending on the substitution on the phenyl ring of benzylic azide. The reaction of para substituted benzylic azides and 2 equivalents of alkenes afforded the corresponding substituted quinolinium salts, while benzylic azides without a para substituent provided biquinolinium salts. The copper-promoted cycloaddition reaction also allows biquinoline products to be obtained from ortho-substituted benzylic azides. These reactions work well with both terminal and internal alkenes. Unsymmetrical internal alkene reactions proceed with high regioselectivity. The reaction is likely started by Lewis acidic CuII-assisted rearrangement of benzylic azide to N-methyleneaniline, followed by a [4 + 2] cycloaddition with alkene. Detailed mechanistic studies suggest that the biquinoline and biquinolinium salts are likely formed via radical processes.
- Chen, Wei-Chen,Gandeepan, Parthasarathy,Tsai, Chia-Hung,Luo, Ching-Zong,Rajamalli, Pachaiyappan,Cheng, Chien-Hong
-
p. 63390 - 63397
(2016/07/19)
-
- A combination of trimethylsilyl chloride and hydrous natural montmorillonite clay: An efficient solid acid catalyst for the azidation of benzylic and allylic alcohols with trimethylsilyl azide
-
We present a new procedure to convert in situ natural montmorillonite clay into a partially acidified one using a catalytic amount of trimethylsilyl chloride and trace water. We demonstrate that the acidic montmorillonite can catalyze the direct azidation
- Tandiary, Michael A.,Masui, Yoichi,Onaka, Makoto
-
p. 15736 - 15739
(2015/02/19)
-
- Copper triflate: An efficient catalyst for direct conversion of secondary alcohols into azides
-
A simple, practical, and efficient strategy has been demonstrated for the direct synthesis of organic azides from alcohols using azidotrimethylsilane (TMSN3) as azide source in the presence of copper(II) triflate [Cu(OTf)2]. A variet
- Khedar, Poonam,Pericherla, Kasiviswanadharaju,Kumar, Anil
-
supporting information
p. 515 - 518
(2014/03/21)
-
- Exploiting the Nucleophilicity of N-H Imines: Synthesis of Enamides from Alkyl Azides and Acid Anhydrides
-
The nucleophilicity of N-unsubstituted imines, which were generated from alkyl azides by a ruthenium-catalyzed reaction, was investigated in the reaction with acid anhydrides. The initial products were N-acylimines, which isomerized to the corresponding e
- Han, Junghoon,Jeon, Mina,Pak, Han Kyu,Rhee, Young Ho,Park, Jaiwook
-
supporting information
p. 2769 - 2774
(2016/02/18)
-
- Reductive azidation of carbonyl compounds via tosylhydrazone intermediates using sodium azide
-
Simple and direct: Aldehydes and ketones can be transformed into alkyl azides through a reductive coupling of the corresponding tosylhydrazones in a process that takes place simply in the presence of K2CO3, tetrabutylammonium bromide
- Barluenga, Jose,Tomas-Gamasa, Maria,Valdes, Carlos
-
supporting information; experimental part
p. 5950 - 5952
(2012/07/03)
-
- Reaction pathway and rate-determining step of the Schmidt rearrangement/fragmentation: A kinetic study
-
The Schmidt rearrangement of substituted 3-phenyl-2-butanone with trimethylsilyl azide in 90% (v/v) aqueous TFA gave two types of product, fragmentation and rearrangement, the ratio of which depends on the substituent: more fragmentation for a more electron-donating substituent. Rate measurements by azotometry indicated the presence of an induction period, and the pseudo-first-order rate constants showed saturation kinetics with respect to the azide concentration. It was indicated that the reaction proceeds through pre-equilibrium in the formation of iminodiazonium (ID) ion and that the N 2 liberation from the ID ion is rate-determining. Under high azide concentration conditions, where the effective reactant is the ID ion, the reaction gave a linear Hammett plot with a value of -0.50. The observed substituent effects on the rate and the product selectivity imply that path bifurcation on the way from the rate-determining TS to the product states occurs, as suggested by previous molecular dynamics simulations, in a similar manner to the analogous Beckmann rearrangement/fragmentation reactions.
- Akimoto, Ryo,Tokugawa, Takehiro,Yamamoto, Yutaro,Yamataka, Hiroshi
-
experimental part
p. 4073 - 4078
(2012/06/29)
-
- A Lewis acid mediated schmidt reaction of benzylic azide: Synthesis of sterically crowded aromatic tertiary amines
-
An efficient one-pot synthesis of sterically hindered aromatic tertiary amines through Lewis acid induced intermolecular Schmidt reaction of benzylic azides is described. In the presence of EtAlCl2, benzylic azide underwent a smooth Schmidt reaction to give the corresponding iminium ion, which, upon reduction with NaBH4 in situ, afforded the tertiary amine. The effects of substituents on the aromatic ring and the steric effects of the alkyl side chain have also been studied.
- Murali, Annamalai,Puppala, Manohar,Varghese, Babu,Baskaran, Sundarababu
-
supporting information; experimental part
p. 5297 - 5302
(2011/11/12)
-
- A mild and efficient method for preparation of azides from alcohols using acidic ionic liquid [H-NMP]HSO4
-
We report here an efficient method for the synthesis and characterization of [H-NMP]HSO4 and its application as an efficient catalyst and solvent for preparation of azides from corresponding alcohols under mild conditions. This processor showed
- Hajipour, Abdol R.,Rajaei, Asiyeh,Ruoho, Arnold E.
-
supporting information; experimental part
p. 708 - 711
(2011/03/17)
-
- Copper(II) triflate as a double catalyst for the one-pot click synthesis of 1,4-disubstituted 1,2,3-triazoles from benzylic acetates
-
Copper(II) triflate doubly catalyzed the substitution of benzylic acetates by TMSN3 and the subsequent 1,3-dipolar addition with an alkyne in one pot. This procedure afforded the preparation of 1,4-disubstituted 1,2,3-triazoles in good yields starting from the easily accessible acetates without isolating an organic azide using a single catalyst. Georg Thieme Verlag Stuttgart.
- Fukuzawa, Shin-Ichi,Shimizu, Eiji,Kikuchi, Satoshi
-
p. 2436 - 2438
(2008/03/28)
-
- Formation and Stability of Ring-Substituted 1-Phenylethyl Carbocations
-
The solvolysis of 1-phenylethyl derivatives with electron-donating 4-substituents in 50:50 trifluoroethanol:water(v:v) occurs at a rate that is independent of azide concentration but gives yields of the corresponding azide adducts of up to 98percent by trapping a carbocation intermediate.Rate constants for reactions of the cations with solvent range from 2 x 103 s-1 (4-Me2N) to 4 x 109 s-1 (4-Me), assuming a diffusion-controlled rate constant of 5 x 109 M-1 s-1 for their reactions with azide and thiol anions.Correlation of the rate constants following the Yukawa-Tsuno treatment gives ρn = 2.5, ρr = 5.2, and r+ = 2.1 for the reaction with trifluoroethanol, and ρn = 2.7, ρr = 4.9, and r+ = 1.8 for the reaction with water.The reverse reaction, acid-catalyzed cleavage of substituted 1-phenylethyl alcohols to give the corresponding carbocation, follows ρn = -4.9, ρr = -4.4, and r+ = 0.9.This gives values of ρn = -7.6, ρr = -9.3, and r+ = 1.2 for formation of the cations at equilibrium.There is an imbalance in the development of resonance delocalization, analogous to the "nitroalkane anomaly", that is consistent with a dependence of the fraction of maximal resonance delocalization on the fraction of rehybridization or C-X bond cleavage.Solvent effects on carbocation stability in aqueous-organic mixtures are relatively small.They depend mainly on the nucleophilicity of the solvent components and a specific solvent effect of trifluoroethanol on the reactivity of hydroxylic nucleophiles, including trifluoroethanol itself.The "ionizing power" of the solvent has only a small effect on cation stability, and there is little effect of the concentration or nature of added salts.
- Richard, John P.,Rothenberg, Marc E.,Jencks, William P.
-
p. 1361 - 1372
(2007/10/02)
-
- Concerted Bimolecular Substitution Reactions of 1-Phenylethyl Derivatives
-
Substituted 1-phenylethyl derivatives with ?+ > -0.08 exhibit bimolecular substitution reactions with azide ion in 20percent acetonitrile in water.The reactions with 1-phenylethyl chlorides follow a Hammett correlation with ρ = -2.9, compared with ρ = -5.6 (r+ = 1.15) for solvolysis.Swain-Scott correlations give values of s = 0.46 and 0.22 for 1-(4-nitrophenyl)ethyl chloride and tosylate, respectively; there are large positive deviations for azide ion and water and negative deviations for cyanide ion.The value of βnuc is 0.09 for reactions of substituted acetates with the chloride.The reactions exhibit ''synergism'' between the nucleophile and leaving group that favors the bimolecular reaction with Me2S, Br- > Cl- > OTs- leaving groups.The bimolecular reaction with azide follows the Grunwald-Winstein Y correlation with m = 0.8 in methanol-water mixtures.Bimolecular reactions with less reactive nucleophiles in the series N3-, CN-, AcO-, and ROH appear at progressively larger ? values, as the carbocation becomes less stable.It is concluded that these reactions are SN2 displacements that proceed through an open, ''exploded'' transition state that closely resembles a carbocation.Specific salt effects are small in water but are significant in acetonitrile-water mixtures and could be mistaken for normal or induced common ion rate depressions.No evidence was obtained for nucleophilic assistance to the formation of a carbocation intermediate.Concurrent SN1 and SN2 pathways occur in the reactions with solvent and azide of dimethylsulfonium ion, 1-(4-fluorophenyl)ethyl chloride, 1-(3-methoxyphenyl)ethyl chloride, and, probably, 1-(3-nitro-4-methoxyphenyl)ethyl chloride.Crude estimates of the lifetime of the carbocation intermediate in the presence of the nucleophile are consistent with the hypothesis that the concerted reactions are enforced by the absence of a significant lifetime of the carbocation in the presence of the nucleophile and that stepwise mechanisms are followed when the intermediate has a significant lifetime; the change from a stepwise to a concerted mechanism occurs when the intermediate ceases to have a lifetime in the presence of a nucleophile.
- Richard, John P.,Jencks, William P.
-
p. 1383 - 1396
(2007/10/02)
-
- Lewis Acid Catalyzed Conversion of Alkenes and Alcohols to Azides
-
Hydrazoic acid, though unreactive to alkenes, adds readily to enol ethers.In the presence of Lewis acids, in particular TiCl4, addition takes place readily to phenylethylenes or 1,1-disubstituted ethylenes to produce alkyl azides.Regiochemical, electronic, and steric influences were explored.TiCl4 also served to catalyze conversion of benzyl or tertiary alcohols to azides.Monosubstituted alkenes or primary alcohols are not affected.
- Hassner, Alfred,Fibiger, Richard,Andisik, Donald
-
p. 4237 - 4244
(2007/10/02)
-
- Reactions of Substituted 1-Phenylethyl Carbocations with Alcohols and Other Nucleophilic Reagents
-
Selectivities of a series of substituted 1-phenylethyl carbocations toward alcohols and other nucleophiles have been determined by product analysis.The 1-(4-dimethylamino)phenyl)ethyl carbocation exhibits a high selectivity in its reactions with alcohols , with KEtOH/KTFE = 140 and βnuc = 0.5.The selectivity for activation-limited reactions with alcohols decreases progressively with increasing reactivity of the carbocation, in contrast to the behavior expected from the N+ scale of reactivity.A sharper drop in selectivity for carbocations that react faster than ca. 109 S-1 is attributed to an approach to limiting rate constants for the more reactive alcohol.The limiting selectivity of kEtOH/kTFE = 2 for carbocations with ks ca. 1011 S-1 may represent reaction from a pool of solvent molecules in which there is a modest charge-dipole interaction between the alcohol and carbocation.The relatively low reactivity of water corresponds to that expected for an alcohol of pKa ca. 13.This is ascribed to an imbalance between charge development and solvation of the transition state compared with H3O+.Substituted acetate anions react with the 1-(4-methoxyphenyl)ethyl carbocation with βnuc = 0.13.The selectivity decreases with increasing cation reactivity as the carboxylate ions approach limiting rate constants of ca. 5 * 108 M-1 s-1.This relatively low limit is attributed to a requirement for desolvation of basic oxygen anions before reaction.A dependence of solvent selectivity on the leaving group shows that the 1-(4-methylphenyl)ethyl carbocation reacts with solvent, in part, through an ion pair.Azide ion reacts from a pool that can be described by an equilibrium constant of Kas = 0.3 M-1.Styrene formation from this carbocation is catalyzed by a leaving carboxylate ion and by added buffers, wih β = 0.14.The equilibrium constant for the formation of a reactive base-cation pair is ca. 0.04 M-1.Rate constants for collapse of the ion pair, to form ester, and for proton removal, to form 4-methylstyrene, were estimated to be approximately 1.6 * 1010 s-1 and 6 * 107 s-1, respectively.The rate constants for deprotonation and for hydration of the styrene give the acid dissociation constant of the carbocation to form 4-methylstyrene, pKA = -11.2.
- Richard, John P.,Jencks, William P.
-
p. 1373 - 1383
(2007/10/02)
-