- IMPROVEMENTS IN OR RELATING TO ORGANIC COMPOUNDS
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A process of converting a carbon-carbon multiple bond to a cyclopropane ring, comprising the addition of a N-alkyl-N-nitroso compound to a mixture of alkene precursor, aqueous base and Pd(II)-catalyst, with the N-alkyl-N-nitroso compound obtained directly from an alkyl amine derivative, NaNO2 and an acid via phase separation of the N-alkyl-N-nitroso compound from the aqueous phase.
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Page/Page column 18-19
(2015/05/06)
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- Ambident ethyl N-nitrosocarbamate anion: Experimental and computational studies of alkylation and thermal stability
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Alkylation of N-nitrosourethane tetrabutylammonium salt (2-Bu4N) with four electrophiles (Mel, Etl, i-Prl, and PhCH2Br) was studied by 1H NMR in CD2Cl2 and CD3CN solutions. The ratio of the three regioisomers N-alkyl-N-nitrosourethane 3, azoxy 4, and O-alkyldiazotate 5 was practically independent of solvent but dependent on the nature of the electrophile. The anion 2 and O-alkyl derivative 5 are thermally unstable and decompose to ethyl carbonates 9 and 10, respectively, with a first-order rate constant (2-Bu4N: k = 18.5 ± 0.1 × 10-5 S-1; 5b (R = Et): k = 1.77 ± 0.02 × 10-5 s-1; 5d (R = PhCH2): k = 4.78 ± 0.08 × 10-5 s-1 at 35 °C in CD2Cl2). Further kinetic measurements gave activation parameters for the decomposition of 2 (Ea = 24.2 ± 0.3 kcal/mol and In A = 30.9 ± 0.1). Gas-phase calculations at the MP2(fc)/6-31+G(d)//MP2(fc)/6-31G(d) level showed that the alkylation of 2 involves the lone electron pairs of the N-N-O atoms, and the calculated activation energies correspond well to the observed ratio of regioisomers 3-5. The theoretical analysis of the decomposition processes supports a concerted mechanism with a four-center transition state in the first step for all four compounds. The calculated activation energy order (2 5 3 4) is consistent with the observed order of stability. Decomposition of 2 and 5 is a unimolecular process, giving carbonates 9 and 10 in a single step. In contrast, rearrangement of 3 and 4 leads to alkyl diazonium ions. A detailed theoretical analysis indicates that the rate-determining step for thermal decomposition of 2 is the loss of molecular nitrogen, while in 5 it is the trans-cis isomerization process. The nonconcerted process involving homolytic cleavage of the O-N bond in 5 was found to be significantly less favorable.
- Benin, Vladimir,Kaszynski, Piotr,Radziszewski, J. George
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p. 14115 - 14126
(2007/10/03)
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- A screening procedure for the formation of nitroso derivatives and mutagens by drug-nitrite interaction
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A general procedure for screening for the formation of nitroso derivatives and/or mutagens by drug-nitrite interaction was established. A test drug (50 mM) was reacted with nitrite (500 mM) at pH 3.0-3.5 and 37°C for 4 h. The residual nitrite in the reaction mixture was decomposed with ammonium sulfamate. The nitrite-free reaction mixture was assayed for both nitroso derivatives and mutagens by colorimetry of Griess reagent-positive substances formed by treatment with hydrogen bromide and by mutagenesis assay using Salmonella typhimurium TA98 and TA100 as tester strains, respectively.
- Takeda,Kanaya
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p. 3399 - 3404
(2007/10/02)
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