title: The photocatalyzed Meerwein arylation: classic reaction of aryl diazonium salts in a new light.
abstract: The use of diazonium salts for aryl radical generation and C-H arylation processes has been known since 1896 when Pschorr first used the reaction for intramolecular cyclizations. Meerwein developed it further in the early 1900s into a general arylation method. However, this reaction could not compete with the transition-metal-mediated formation of C(sp(2))-C(sp(2)) bonds. The replacement of the copper catalyst with iron and titanium compounds improved the situation, but the use of photocatalysis to induce the one-electron reduction and activation of the diazonium salts is even more advantageous. The first photocatalyzed Pschorr cyclization was published in 1984, and just last year a series of papers described applications of photocatalytic Meerwein arylations leading to aryl-alkene coupling products. In this Minireview we summarize the origins of this reaction and its scope and applications.
authors.affiliation: Department of Chemistry and Pharmacy, Universität Regensburg, Universitätsstrasse 31, 93040 Regensburg, Germany.
authors.forename: Durga Prasad
authors.initials: DP
authors.lastname: Hari
authors.forename: Burkhard
authors.initials: B
authors.lastname: König