143722-58-1Relevant articles and documents
Intramolecular Addition Reactions of Functionalized Arylcarbenes to Arenes
Guth, Michael,Kirmse, Wolfgang
, p. 606 - 613 (2007/10/02)
carbenes with Ar = phenyl (16), 1-naphthyl (20), and 2-furyl (24) have been generated photolytically from appropriate diazo or tosylhydrazone precursors.Intramolecular addition to the arene prevailed in pentane solution, insertion into ortho C-H bonds of the arene being a minor process.On direct photolysis in methanol, intermolecular O-H insertion predominated over intramolecular addition to phenyl and 1-naphthyl groups (kS OH).The ratio of addition to O-H insertion was not affected by benzophenone sensitization in the case of Ar = Ph, but increased strongly in the case of Ar = 1-naphthyl.These data, implying kT > kTS for 20, constitute the first evidence for the addition of triplet arylcarbenes to arenes.Ar = 2-furyl was found to promote the intramolecular addition of both singlet 24 (kS ca. kOH) and triplet 24 (kT > kTS).The reactivity of arenes toward electrophiles (kS) and the stabilization of diradical intermediates (kT) is thought to account for the observed trends.