- Acyl iodides in organic synthesis. Reaction of acyl iodides with N,N-dimethyl carboxylic acid amides
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Acyl iodides RCOI (R = Me, Ph) reacted with N,N-dimethylformamide and N,N-dimethylacetamide Me2NC(=O)R' (R' = H, Me) along two concurrent pathways involving transacylation and cleavage of the Me-N bond. The first pathway leads to the formation of acyl group exchange products, and the second, to the corresponding imides R'CON(Me)COR.
- Voronkov,Tsyrendorzhieva,Rakhlin
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- Mid, and near-IR study of the hydrogen bond interaction between N- methyldiacetamide and phenols
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The hydrogen bond complexes between phenol derivatives (pK(a) = 10.20- 8.20) and N-methyldiacetamide (NMD) are studied by mid- and near-IR spectroscopy in carbon tetrachloride solution. The equilibrium constants and enthalpies of complex formation are determined and the results suggest that the proton acceptor ability of NMD is lower than that of monocarbonyl bases. Complex formation results in decoupling of the v(C=O) vibration. The frequencies and intensities of the bonded v(OH) vibration are determined for the fundamental and first overtone transition. Hydrogen bond formation results in a very weak increase of the mechanical anharmonicity and a strong decrease of the intensity of the first overtone of the OH stretching vibration. The first (μ1) and second (μ2) dipole moment derivatives are calculated. In this limited domain, a linear correlation is found between Δ1 and Δ2, the increase of the dipole moment derivatives resulting from hydrogen bond formation.
- Leroux,Samyn,Zeegers-Huyskens
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- Reaction of iodo(trimethyl)silane with N,N-dimethyl carboxylic acid amides
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The reactions of iodo(trimethyl)silane with N,N-dimethylformamide and N,N-dimethylacetamide Me2NCOR (R = H, Me) at a molar ratio of 1: 2 involved mainly cleavage of the N-C(=O) bond with formation of up to 80% of N,N-dimethyltrimethylsilylamine Me3SiNMe2 and the corresponding acyl iodide RCOI. In the reaction with N,N-dimethylformamide, formyl iodide HCOI was detected for the first time by gas chromatography-mass spectrometry. The contribution of Me-N bond cleavage, leading to N-methyl-N-trimethylsilyl derivative Me(Me3Si)NCOR and methyl iodide was considerably smaller. Another by-product was the corresponding N-methyl imide MeN(COR)2 formed by reaction of the initial amide with acyl iodide. The primary intermediate in the reaction of iodo(trimethyl)silane with DMF and DMA is quaternary ammonium salt [Me2(Me3Si)N +COR] I- which decomposes via dissociation of the N-CO and N-Me bonds.
- Voronkov,Tsyrendorzhieva,Lis,Rakhlin
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experimental part
p. 791 - 793
(2010/10/04)
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- Gas-phase Pyrolytic Reactions. Part 5. Rate Data for Pyrolysis of N-t-Butyl- and N-Acetyl-benzamide, N-Acetyl-N-methylacetamide, and N-Ethyl- and N-Prop-2-yl-thioacetamide
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The rates of gas-phase elimination of N-t-butylbenzamide 1, N-acetylbenzamide 2, and N-acetyl-N-methylacetamide have been measured in the ranges 674-734, 580-620 and 696-765 K, respectively.The compounds undergo unimolecular first order elimination reactions for which log A = 11.1, 13.7 and 10.5 s-1 and Ea = 172.6, 171.7 and 167 kJ mol-1, respectively.At 600 K, the following reactivity ratios are observed: 1 : N-t-butylacetamide 3, 260; t-butyl benzoate 4 : t-butylacetate 5, 2.3; N-acetylacetamide 6 : N-acetyl-N-methylacetamide, 290; and 2 : 6, 3.6.These relative rate factors show that the phenyl group increases the rate of thermolysis due to its electron-withdrawing ability 250 times more for simple amides than for esters and diamides.These relative rate differences are highly affected by the nature of the Cα-X bond.The pronounced effect of the phenyl group on simple amides could be explained in terms of the low polarity of the Cα-NH bond relative to the more polar Cα-O bond in esters.On the other hand the pronounced deactivation effect of the methyl group in N-acetyl-N-methylacetamide is highly reflected in the reactivity ratio of 290 between 6 and N-acetyl-N-methylacetamide which could be explained in terms of the greater bond order of the Cα-X bond in the latter than in the former.Furthermore, the small reactivity ratio in the diamides 2 and 6 is consistent with the fact that resonance between the lone-pair of electrons on X and the α-carbonyl group increases the Cα-X bond order, thus rendering the Cα-X bond breakage more difficult.We have also measured the rates of thermolysis of N-ethylthioacetamide and N-prop-2-ylthioacetamide.The relative primary : secondary : tertiary rates at 600 K of 1 : 1.3 : 1.5 for the thioamides suggests that the transition state for this class of compound is much less polar than that for the thioacetates.
- Al-Awadi, Nouria A.
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p. 2187 - 2189
(2007/10/02)
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- Synthesis and properties of (O-acyl imidato)carbene complexes of chromium, molybdenum, and tungsten
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A number of (O-acyl imidato)carbene complexes of chromium, molybdenum, and tungsten were prepared by the acylation of aminocarbenes or by the reaction of acetoxycarbenes with amides. These relatively unstable complexes had unusual spectroscopic properties and underwent thermal reactions with imines to give low yields of 3-azetidinones. Two amido chromium carbene complexes were also prepared. These were quite unstable, resembling acetoxycarbenes, and readily decomposed. An (N-carbobenzoxy-amino)carbene was also prepared. It was the most stable of these carbenes and underwent reactions typical of aminocarbene complexes.
- Hegedus, Louis S.,Schultze, Lisa M.,Montgomery, John
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p. 2189 - 2195
(2008/10/08)
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