Picosecond Radical Kinetics. Fast Ring Openings of Secondary and Tertiary trans-2-Phenylcyclopropylcarbinyl Radicals

Unraveling the Mechanism of the Singlet Oxygen Ene Reaction: Recent Computational and Experimental Approaches

“…Alternatively, the existence of an open biradical/dipolar intermediate (OI, Scheme 8) could yield rearranged products. Specifically, if an OI intermediate with a lifetime greater than 10 À11 -10 À12 s [42,48] had been formed, the ring-opened products should have been detected. At this point, it is pru-Scheme 6.…”

Selective Intermolecular Amination of CH Bonds at Tertiary Carbon Centers

“…The rate constant for ring opening of trans - 11 has been measured at 7 × 10 10 s −1 , which is appropriate for detection of radicals having picosecond lifetimes. [26] In the amination event with cis - 11 , generation of 1–4 % of trans -cyclopropane 12 gives evidence for the intermediacy of a cyclopropylcarbinyl radical, which undergoes subsequent reversible cyclopropane ring opening. The identical outcomes for TcesNH 2 and DfsNH 2 in this, the KIE, and stereospecificity experiments lead us to conclude that steric effects between the nitrenoid complex and substrate principally govern product selectivity (see Table 2).…”

Evolution of neutral organic super-electron-donors and their applications

“…In the proposed mechanism, SET from the photoexcited donor 126 to arene cis-187 generates radical-anion cis-187 ra closed. Similar to the Newcomb 60 and Ingold 61 studies, the presence of a cyclopropane ring next to the radical site would lead to spontaneous opening of the cyclopropane ring to form 187 ra open. If the cyclopropane ring-opening is reversible, it will generate again the radical-anion of the arene 187 ra closed, with diminished stereochemical purity.…”