Exploratory and mechanistic studies of the electron-transfer-initiated photoaddition reactions of allylsilane-iminium salt systems

Ohga, Kazuya; Yoon, Ung Chan; Mariano, Patrick S.

doi:10.1021/jo00176a001

Cited by 84 publications

(20 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This process increases the rate of heterolytic fragmentation and has been proven to be a useful method for the generation of radicals for synthetic purposes. 1b,e-i,m The most common reaction of cation radical intermediates is α-heterolytic fragmentation with loss, or transfer to the solvent or to a nucleophile, of an electrofugal group (X + ), as shown in Scheme . Arene cation radical α-deprotonation, , desilylation, , and decarboxylation are the most common fragmentations of this type. Most studies in this area have been devoted to deprotonation and are based on product distribution analysis, ,,6a or the measurement of absolute rates ,6d,, and their response to variations in base strength − or to steric and electronic effects.…”

Section: Introductionmentioning

confidence: 99%

A Kinetic Evaluation of Carbon−Hydrogen, Carbon−Carbon, and Carbon−Silicon Bond Activation in Benzylic Radical Cations

et al. 1998

View full text Add to dashboard Cite

A detailed study of the competition between C−C, C−H, and C−Si bond fragmentation in a series of 4-methoxy-α-substituted toluene radical cations (1 • + ), involving both product studies and kinetic analysis, is presented. C−C bond fragmentation occurs with several radical cations in acetonitrile. The rate constants for such processes, determined by laser flash photolysis, varied from 2.8 × 104 (1c • + ) to 1.53 × 106 (1f • + ) s-1. The activation parameters for C−C bond fragmentation are characterized by low activation enthalpies on the order of 30 kJ mol-1 and negative activation entropies in the range −34 to −55 J mol-1 K-1. Deprotonation of the radical cations is always a second-order process induced by nucleophiles [cerium(IV) ammonium nitrate (CAN) or nitrate anion], with second-order rate constants from 7.7 × 107 (1h • + ) to 8.8 × 108 (1i • + ) M-1 s-1 in neat acetonitrile (CAN assisted) and from 0.4 × 108 (1j • + ) to 7.1 × 108 (1i • + ) M-1 s-1 in the presence of nitrate anion. The rate constant for nitrate-induced decarboxylation was higher, 13.6 × 108 M-1 s-1 (1d • + ). In a few cases C−C (1e • + , 1f • + ) and C−Si (1g • + ) fragmentations occurred, also as second-order processes induced by nitrate, with rate constants from 4.4 × 108 (1f • + ) to 8.2 × 108 (1g • + ) M-1 s-1. ΔH ⧧ and ΔS ⧧ had opposing influences on C−H and C−C fragmentation, and in the case of 1e • + a temperature-dependent product distribution was obtained. The activation parameters for the observed C−H, C−C, and C−Si fragmentations have been compared, and suggest a rationale for the mechanisms and selectivity of such processes in radical cations.

show abstract

Section: Introductionmentioning

confidence: 99%

A Kinetic Evaluation of Carbon−Hydrogen, Carbon−Carbon, and Carbon−Silicon Bond Activation in Benzylic Radical Cations

et al. 1998

View full text Add to dashboard Cite

show abstract

“…Mariano and his coworkers developed the intra-and intermolecular photoadditions of the radical cations and the radicals derived from them to the = N-C ° radical [130][131][132]. Although they are summarized in his review article [3,[133][134][135], some examples are shown in Scheme 44.…”

Section: Addition To C = X Bondsmentioning

confidence: 99%

Addition and cycloaddition reactions via photoinduced electron transfer

Mizuno

Otsuji

1994

Electron Transfer I

View full text Add to dashboard Cite

“…Mariano (1983aMariano ( , 1983b has ably reviewed the topic. Certain silicon containing iminium salts undergo p.e.t.-induced desilylation (Chen et al, 1983;Ohga et al, 1984). Allenes photoadd to 2-phenyl-1-pyrrolinium perchlorate (Somekawa et al, 1984).…”

Section: Organic Compoundsmentioning

confidence: 99%