A family of low molecular-weight, organic catalysts for reductive C–C bond formation

Abstract

Hydrazines form a new family of low molecular-weight reducing agents for diazonium salts. Using only small amounts of hydrazine catalyst, the coupling of diazonium salts to a variety of reactive partners has been achieved, without the requirement for either metal adjuvants or irradiation with visible or ultraviolet light. The generality of the concept proposed herein as well as its advantages in the preparative scale is outlined and discussed.

Salicylic Acid‐Catalyzed Arylation of Enol Acetates with Anilines

“…In particular, aryldiazonium salts have been also used as aryl radical sources which, after interception with enol acetates, have furnished α-aryl ketones. Selected examples illustrating the implementation of this strategy are: (a) the αarylation of methyl ketones promoted by stoichiometric amounts of KOAc [13] (Scheme 1a); (b) the visible-light induced transformation with [Ru(bpy)3] 2+ as photocatalyst [14] (Scheme 1b); and (c) the use of hydrazines as organocatalysts [15] (Scheme 1c). Closely related methods for the oxidative arylation of vinyl arenes with aryl diazonium salts have also been developed, employing stoichiometric amounts of ascorbic acid as promoter [16] or visiblelight photoredox catalysis [17] .…”

Visible‐Light, Metal‐Free α‐Amino C(sp3)–H Activation through 1,5‐Hydrogen Migration: A Concise Method for the Preparation of Bis(indolyl)alkanes

“…Our group recently discovered that simple aliphatic hydrazines can also be used as catalysts for the reductive activation of diazonium salts for radical transformations, without the requirement for irradiation with visible (or UV) light 18. In agreement with that finding, the use of 4‐aminomorpholine ( 9 , 0.1 equiv.)…”

Metal-Free Oxidative Cross-Coupling Reaction of Heteroaromatic and Related Compounds

“…Transition metal-catalyzed C-H activation cross-coupling of aromatic compounds with aryl halides has emerged as an efficient synthetic tool for the construction of functional biaryl compounds. [21][22][23][24][25][26][27] Recently, novel metal-catalyzed cross-coupling reactions of heteroaromatic compounds have been developed by Gaunt, 28) Sames, 29,30) Sanford, 31) Glorius, 32,33) Ackermann, 34,35) Itami, [36][37][38] and Larrosa. 39,40) However, these reactions have several limitations, such as harsh reaction conditions, the need for metal catalysts, and the use of excessive amounts of substrate.…”