Cationic Arylation. III. Comparison of Phenylation of Naphthalene with Phenyl Cation and Phenyl Radical

Abstract

Naphthalene was phenylated with phenyl cation (from PhN2BF4) or phenyl radical (from PhN2BF4+NaNO2) in dimethyl sulfoxide. Partial rate factors for phenyl radical were somewhat larger than those reported with the phenyl radical generated from N-nitrosoacetanilide. Partial rate factors for phenylation with phenyl cation were smaller than those for free radical phenylation and those for common electrophilic substitution reactions. These small partial rate factors for phenyl cation were not compatible with the reaction scheme involving an ordinary σ-complex, and a mechanism involving a spiro cation appeared to be plausible.

Synthesis and Reactivity of [closo-1-CB9H9-1-N2]: Functional Group Interconversion at the Carbon Vertex of the {closo-1-CB9} Cluster

“…Thus, pyridine has one of the highest nucleophilicity parameters, whereas acetonitrile has one of the lowest nucleophilicity parameters. , Therefore, the former may induce radical generation, while the latter will favor cationic processes. This is indeed observed experimentally for the decomposition of both 1 (present work) and benzenediazonium salts − for which the corresponding acetamides are the main products in MeCN solutions (see Scheme ).…”

“…54,55 Therefore, the former may induce radical generation, while the latter will favor cationic processes. This is indeed observed experimentally for the decomposition of both 1 (present work) and benzenediazonium salts [56][57][58][59][60] for which the corresponding acetamides are the main products in MeCN solutions (see Scheme 7).…”

(Sensitized) Photolysis of Diazonium Salts as a Mild General Method for the Generation of Aryl Cations. Chemoselectivity of the Singlet and Triplet 4-Substituted Phenyl Cations

“…28 Due to the singlet multiplicity of the diazonium salt ground state and the energy order of the aryl cations, in thermal decomposition only the singlet aryl cation chemistry is expected and indeed observed. [13][14][15][16][17][18][19][20][21] This is not necessarily the case for the photodecomposition.…”

“…Changing the medium from a water−alcohol mixture 14 to neat alcohol significantly increases the likelihood that a radical will be formed . Among polar nonprotic solvents, acetonitrile , favors the cations, whereas in DMF or DMSO , radicals are formed. The mild photochemical decomposition affords a more convenient entry to aryl cations…”

Theoretical study of the triplet state aryl cations recombination: A possible route to unusually stable doubly charged biphenyl cations

“…The singlet state cations easily react with the surrounding environment and are nonselective in electrophilic reactions . The triplet state aryl cations are much more selective and react predominantly with olefins and aromatic compounds providing the arylated products . For instance, the cationic arylation of benzene yields the biphenyl molecule, which is schematically illustrated in Figure …”