Salicylic Acid‐Catalyzed One‐Pot Hydrodeamination of Aromatic Amines by tert‐Butyl Nitrite in Tetrahydrofuran

Abstract

A significant acceleration in the hydrodeamination of in situ formed diazonium salts (from aromatic amines) has been observed in the presence of 10-mol% salicylic acid, using tetrahydrofuran as the hydrogen donor. The reaction proceeds efficiently at 20 8C for a wide range of substituted anilines, even at 10-mmol scale, without any other additive. The same protocol has been adapted to the selective deuterodeamination of some aromatic amines. Control experiments clearly show that aryl radicals are involved in the reaction mechanism.

Salicylic Acid‐Catalyzed Arylation of Enol Acetates with Anilines

“…Inspired by their work, we have recently developed the hydrodeamination of in-situ formed diazonium salts, catalyzed by salicylic acid (SA) and using THF as the hydrogen donor. [20] Given that SA is inexpensive, harmless and a renewable feedstock, it could be an ideal catalyst to generate aryl radicals; therefore, we decided to elaborate this concept for the α-arylation of enol acetates. In our previous work, we proposed that the in-situ formed diazonium salts (A) could undergo a nucleophilic addition of salicylic acid to form the aryl diazobenzoate B (not isolated), [21] which upon N-O bond homolysis, would generate N2, the aryl radical (D) and the H-bond stabilized salicyloyl radical (C).…”

tert‐Butyl Nitrite (TBN), a Multitasking Reagent in Organic Synthesis

“…The notable feature of this reaction is the selective deuterodeamination of aromatic amines by using [D 8 ]THF which affords the deuterated product in excellent isotopic purity. A large KIE value ( k H / k D =2.70) suggests that H‐abstraction from THF is the rate‐determining step of the reaction …”

“…Through controle xperiments,i tw as revealed that THF is the hydrogen source.T he notable feature of this reactioni st he selective deuterodeamination of aromatic amines by using [D 8 ]THF which affords the deuterated product in excellent isotopicp urity.Al argeK IE value (k H /k D = 2.70) suggestst hat H-abstractionf rom THF is the rate-determining step of the reaction. [31] Several methods have been reported and widely employed for the direct allylation of aromatic compounds.D espite of its versatility,t heir application in organic synthesis on large scale is somewhat restricted because severalo ft hese approaches use toxic catalysts or reagents, shows lack of functionalg roup tolerance or poor regioselectivity.T he most general and mildest method for the introduction of allyl group is via af ree radical reaction. Inspired by this, in 2002, Frejd group disclosed a metal-free diazotizatived eamination strategy for the synthesis of allyl aromatic compounds (18)u sing TBN.…”

Metal‐Free Arylation‐Lactonization Sequence of γ‐Alkenoic Acids Using Anilines as Aryl Radical Precursors

“…As previously found by other authors in a similar arylation‐lactonization sequence, the addition of H 2 O to the solvent mixture had a positive impact on the reaction yield, being acetonitrile better solvent than acetone (entries 2–4). Following our previous works,, we examined the addition of 10 mol‐% of SA (entry 5), obtaining superior yields when 10 equivalents of H 2 O were also added (entries 6 and 7). Aware by the work of other authors that the transformation of in‐situ formed diazonium salts into aryl radicals could also be promoted by inorganic bases, we examined the influence of sodium carbonate, potassium carbonate and potassium acetate (entries 8–10).…”

“…Inspired by the work of Carrillo and co‐workers, we have recently developed the hydrodeamination of in‐situ formed diazonium salts, catalyzed by salicylic acid (SA) and using THF as the hydrogen donor . We also used this simple and environmentally friendly generation of aryl radicals to obtain α ‐aryl ketones from enol acetates and anilines .…”