- N-centered radicals in self-terminating radical cyclizations: Experimental and computational studies
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(Chemical Equation Presented) Intermolecular addition of photochemically generated N-centered aminium and amidyl radicals 13a-d and 16a,b, respectively, to the cyclic alkyne 1 initiates a radical translocation/cyclization cascade, followed by an oxidative termination step that eventually leads to formation of the bicyclic ketones 7a and 8a. Computational studies were performed to gain insight into the mechanism of these reactions, which are an interesting modification of the recently discovered concept of self-terminating radical cyclizations.
- Wille, Uta,Heuger, Gerold,Jargstorff, Christian
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- A Study of Essentially Free Carbocations Derived via Diazonium and Oxo Diazonium Ions in the Liquid Phase
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Nitrogen- and nitrous oxide-separated ion pairs containing 4-substituted benzyl cations and carboxylate or tosylate anions were prepared by thermolysis of N-nitroso- and N-nitroamides, acidification of phenyldiazomethane, and nitrosation of N-benzyl-O-benzoylhydroxylamine. The cations were generated in benzene/toluene and benzene/anisole mixtures and were found to partition between the counterion and the solvent and between the aromatic cosolvent and benzene. A familial relationship among the methods was observed. As the cation became more reactive, the yield of solvent-derived products (SDPs) rose and the ratio of rate constants for its reaction with toluene versus benzene, kT/kB, fell. The yield of SDP also rose as the temperature was decreased and as N2 was replaced by N2O; however, kT/kB remained unchanged. Inert diluents had no effect on kT/kB but decreased hydrocarbon yield by 40% on 2-fold dilution. In the presence of reactive diluents that are converted into secondary alkylating agents, both the % hydrocarbon and kT/kB rose. These results are interpreted in terms of the intermediacy of inert-molecule-separated ion pairs (IMSIPs) in deamination. The cation reacted with benzoates and tosylates not only at the oxygens but also at the ipso carbon; subsequent decarboxylation and desulfonylation, respectively, led to diphenylmethanes. The ester/SDP ratio is introduced as a new measure of carbocation reactivity.
- Darbeau, Ron W.,White, Emu H.,Song, Fenhong,Darbeau, Nyla R.,Chou, James
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p. 5966 - 5978
(2007/10/03)
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- Reaction of amides with nitric oxide (NO)
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Amides were allowed to react with nitric oxide in aprotic and non- ethereal solvents to give the corresponding N-nitroso derivatives. The reaction was accelerated by addition of oxygen. The solvent effect revealed that the reaction did not proceed in the presence of protic media.
- Itoh, Takashi,Nagata, Kazuhiro,Matsuya, Yuji,Miyazaki, Michiko,Ohsawa, Akio
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p. 5017 - 5020
(2007/10/03)
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- Reaction of N-Nitroso-N-benzylformamide with Phenylmagnesium Bromide and Phenyllithium
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The action of aryl Grignard and lithium reagents on N-nitroso-N-benzylformamide (1) leads to products whose formation can be understood in terms of the intermediacy of benzyldiazotate ion.However, the presence of "hydrogen abstraction" products, e. g., anisole or naphthalene, coupled with the near absence of products traceable to the aldehyde moiety (expected from the attack at the formyl group) with 1 equiv of organometallics, suggests the initial formation of a complex.Possible rationalizations for the formation of the products are presented.
- Nakajima, Masayuki,Anselme, Jean-Pierre
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p. 2492 - 2496
(2007/10/02)
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