Alkyl nitrate nitration of active methylene compounds. 16. Nitration of alicyclic ketimines

Feuer, Henry; McMillan, Richard M.

doi:10.1021/jo01333a032

Cited by 13 publications

(6 citation statements)

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“…In the derivatives with R2 and/or R 3 = H, the Z-isomer can form an intramolecular hydrogen bond. According to the literature 10,[15][16][17][18][19][20][21][22] these compounds show weak IR and Raman v,(NO,), and strong IR and weak Raman v,(NO,) bands, both displaced to low frequencies, and a strong IR (weak Raman) band at ca. 1630 cm-' attributable to v(C=C) or to v(C=N) of C-N with high bond order.…”

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confidence: 99%

Spectral properties and isomerism of nitroenamines. Part 3

Chiara¹,

Gómez-Sánchez²,

Bellanato³

1992

J. Chem. Soc., Perkin Trans. 2

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Vibrational, N M R and dynamic N M R spectra, considered together with the results of theoretical studies, provide a complete and fairly accurate quantitative picture of the isomerism affecting the nitroenamines R2R3N-C( 1 ) R'=C(2) H-NO, (R' = H, Me). The compounds with primary or secondary amino groups ( R2 and/or R3 = H) exist as solvent-dependent equilibrium mixtures of the intramolecularly hydrogenbonded Z-form and the €-form; the latter isomer can adopt the Z and/or the € conformation around the C(1)-N single bond when R2 # R3. The compounds with a tertiary amino group exist solely in the Eform. Vibrational couplings occur inside the mesomeric system leading to an IR strong (medium or weak Raman) 'enamine' band at 1650-1550 cm-', the result of the asymmetrical coupling of the C=C and C( 1 )-N stretching modes, and when R' and R2 = H, with contributions of the in-plane N-H and C( 1 )-H bending modes. The N-0 stretchings do not contribute to the enamine band, but couple with other vibrations to give a weak IR and Raman band at 1530-1 480 cm-', with a main contribution of the v,(NO,), and a strong IR (medium or weak Raman) band, mainly v,(NO,), at 1280-1230 cm-'. The energy barriers to rotation around the C(l)=C(2) and C(1)-N bonds, and the AGt values for the ionization of the N-H group, indicated that the €e Z isomerization takes place by a thermal mechanism with dipolar transition state, with the contribution, in some of the compounds with an NH group, of an anionic mechanism.Nitroenamines have attracted interest because of their potential use in organic synthesis and their biological a ~t i v i t y . ~ A knowledge of the isomerism and electron distribution inside these mesomeric systems is of paramount importance in understanding their properties and reactivity. As in similar push-pull ethylenes, spectroscopic techniques combined with theoretical studies can provide information on these matters, and we have previously reported on the NMR and vibrational spectra of 3-amino-2-nitroacrylic (1) and 3-amino-2-nitro-NO2 C02Me R2 R3N C( R1 ) ==( 1 R ' = H 2 R L M ~ NO2 R2R3NC( R 1 ) 7 ( 3 R ' = H 4 R'=Me * The symbols indicate, in the order shown, the configuration around the C(l)=C(2) bond and the conformation around the C(1)-N single bond.

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mentioning

confidence: 99%

Spectral properties and isomerism of nitroenamines. Part 3

Chiara¹,

Gómez-Sánchez²,

Bellanato³

1992

J. Chem. Soc., Perkin Trans. 2

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“…The known title compound N ‐(cyclopentylidene)‐ tert ‐butylamine ( 1 ) was prepared from cyclopentanone and tert ‐butylamine (3 equiv.) with TiCl 4 (0.52 equiv.…”

Section: Resultsmentioning

confidence: 99%

“…56 – 62 °C /12 Torr (Ref. : 69 – 70 °C/20 Torr) and consisted of ketimine 1 and its enamine 1A (82:18). 1 H‐NMR of 1 ((D 6 )benzene, 400 MHz): 1.27 ( s , 9 H, t Bu); 1.36 ( quint ., 3 J = 6.9, CH 2 (3)); 1.50 ( quint ., 3 J = 6.9, CH 2 (4)); 1.94 ( t , 3 J = 7, CH 2 (2)); 2.27 ( t , 3 J = 7.3, CH 2 (5)).…”

Section: Methodsmentioning

confidence: 99%

“…The presence of other basic contaminants thwarted our attempts to establish the absence of a 2,5-isomer of Scheme 3. Intermediates and products of LDA-mediated methylation on the 2,2-route (bold arrows); Me = methyl, 14; however, the acid-catalyzed, de-aminating hydrolysis (GP3) afforded a 55% yield of the known 6 2-isopropyl-2-methylcyclopentanone (15) without the 2,5isomer. This confirmed the 2,2-regiospecific process as far as the missing 2,5-ketimine would have been expected to be hydrolyzed faster than 14K.…”

Section: Methodsmentioning

confidence: 99%

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Regioselective Dialkylations of N‐(tert‐Butyl)iminocyclopentane via Deprotonating One‐Pot Procedures

Knorr

Neuner

2018

Helvetica Chimica Acta

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The title compound (1) was chosen as a model for the α/α′‐regioselectivity of deprotonation and subsequent alkylation adjacent to the C=N bond. With the bulky base lithium N,N‐diisopropylamide (LDA) as a catalyst, the one‐pot deprotonation steps can be performed through titration with methyllithium, using gas‐volumetric observation of the liberated methane. In the first step with ensuing methylation by iodomethane, the primary product is born at −40 °C in its metastable (Z) configuration (kinetic control) and may be either isolated or converted in situ at 30 °C into its thermodynamically favored (E)‐isomer via cis to trans stereoinversion at the N‐atom. Being slow enough on the laboratory time scale, this stereoinversion process can serve to control the regioselectivity of the second deprotonation/alkylation sequence as follows. The α,α′‐products are formed from the intermediate (Z)‐imine, whereas α,α‐products result from the intermediate (E)‐imine; in either case, syn deprotonation (cis to tBu at nitrogen) by LDA is apparently disfavored by the tBu group, so that anti deprotonation becomes obligatory. If a third one‐pot deprotonation step is too slow with LDA, it may be performed with the stronger base butyllithium/HMPA which, however, reacts regio‐unselectively. Regioselective one‐pot, LDA‐catalyzed deprotonation with alkylation by oxiranes (alone, or alternatingly with iodomethane) opens a short access to spiro‐[2.4]heptan‐4‐ones.

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“…Some of the recent methods entail the reaction of β-halo- [18][19][20], β-alkylthio-[21], β-alkylsulfinyl- [22] or β-alkoxynitroethenes [23,24] with an amine. Other methods are transamination [25], nitration of imines [26,27] rearrangement of N-nitroenamines [28] and the reaction of phenyl acetylene with aniline in the presence of mercury (II) chloride [29]. Despite all merits, the above-mentioned methods suffer from major drawbacks such as the requirement for the pre-preparation of the appropriate precursors, the toxicity of the catalyst and low efficiency.…”

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confidence: 99%

Green synthesis of nitroenamines by γ-Fe2O3@SiO2–OSO3H nanoparticles as a highly efficient and magnetically separable catalyst

2014

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in organic syntheses either as support or as catalyst [1][2][3][4]. Using them as support results in the straightforward separation of the catalyst from the reaction mixture (this is only achieved using an external magnet). Therefore, we have turned our attention to these systems [5][6][7][8]. This time, we report the synthesis of the nitroenamines facilitated by γ-Fe 2 O 3 @SiO 2 -OSO 3 H as an efficient catalyst. The foregoing catalyst has recently been prepared in our laboratory and used in the synthesis of miscellaneous organic compounds [9].Nitroenamines, olefins with an electron-donating amino group attached to one side and the strongly electron-withdrawing nitro group to the other, are indispensable compounds in organic synthesis. They show substantial pharmacological properties [10,11], and are also utilized as synthetic intermediates [12][13][14][15][16][17]. Nevertheless, there are only a few synthetic methods, reported in literatures, for the synthesis of these compounds. Some of the recent methods entail the reaction of β-halo- [18][19][20], β-alkylthio-[21], β-alkylsulfinyl- [22] or β-alkoxynitroethenes [23,24] with an amine. Other methods are transamination [25], nitration of imines [26,27] rearrangement of N-nitroenamines [28] and the reaction of phenyl acetylene with aniline in the presence of mercury (II) chloride [29]. Despite all merits, the above-mentioned methods suffer from major drawbacks such as the requirement for the pre-preparation of the appropriate precursors, the toxicity of the catalyst and low efficiency. Amongst all reports, the condensation reaction of the nitromethane with orthoformates and amines in the presence of p-toluene sulfonic acid as catalyst seems to be superior, due to easily accessible starting materials [30]. However, it still suffers from the shortcoming of low reaction yields. Also this procedure does not benefit from the feature of reusability and recovery of the catalyst. This prompted us to innovate a heterogeneous, and reusable Abstract Some derivatives of nitroenamines were synthesized in moderate to good yields in the presence of sulfonic acid supported on silica-modified maghemite (γ-Fe 2 O 3 @SiO 2 -OSO 3 H) as a highly efficient and magnetically separable catalyst. Both up to five times recyclability and the magnetic separation are salient features of this catalytic system.

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Alkyl nitrate nitration of active methylene compounds. 16. Nitration of alicyclic ketimines

Cited by 13 publications

References 0 publications

Spectral properties and isomerism of nitroenamines. Part 3

Spectral properties and isomerism of nitroenamines. Part 3

Regioselective Dialkylations of N‐(tert‐Butyl)iminocyclopentane via Deprotonating One‐Pot Procedures

Green synthesis of nitroenamines by γ-Fe2O3@SiO2–OSO3H nanoparticles as a highly efficient and magnetically separable catalyst

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