Functionalized alkoxy arene diazonium salts from paracetamol

Abstract

Arene diazonium tetrafluoroborates can be synthesized from aromatic acetamides via a sequence of deacetylation, diazotation and precipitation, induced by anion exchange. The reaction is conducted as a convenient one-flask transformation with consecutive addition of the appropriate reagents. Exchange of solvents or removal of byproducts prior to isolation of the product is not required. The arene diazonium salts are isolated from the reaction mixture by simple filtration. Two complementary protocols are presented, and the utility of the reaction is exemplified for a synthesis of the diarylheptanoid natural product de-O-methyl centrolobine.

Mizoroki–Heck Reactions with 4‐Phenoldiazonium Salts

“…Therefore, the phenolacetanilides 2c, e, g, i were subjected to the conditions of the aforementioned one-flask deacetylation-diazotation-precipitation sequence. [30,31] The same method has previously been used by us for the synthesis of O-alkylated arenediazonium salts 1a, b, d, f, h. [31] The carboxylic acid and ester-substituted derivatives 1j-l were more conveniently obtained from the corresponding anilines by diazotation with NaNO 2 in HBF 4 (Table 1).…”

“…1b and a number of other O-alkylated derivatives were obtained via a one-flask deacetylation-diazotation sequence from paracetamol and other substituted acetanilides. [30] While this approach was eventually successful, [31] considerable experimentation was required to find suitable conditions for the debenzylation step. These problems provoked the interesting question if a phenol protecting group is actually necessary for Pd-catalyzed transformations with arenediazonium salts.…”

Ru‐ and Pd‐Catalysed Synthesis of 2‐Arylfurans by One‐Flask Heck Arylation/Oxidation

“…To overcome these drawbacks we sought an alternative route not based on furan cross-coupling reactions. Inspired by recent research in our group directed towards the synthesis of centrolobines [16] and related diarylheptanoids [17] through Heck coupling reactions of dihydropyrans and arenediazonium salts, [18] we decided to investigate the feasibility of a synthesis as outlined in Scheme 1. Scheme 1.…”

Pd‐Catalyzed [2+2+1] Coupling of Alkynes and Arenes: Phenol Diazonium Salts as Mechanistic Trapdoors

“…We became interested in this mechanistic dichotomy in the course of our recent research directed at the synthesis of electron-rich arene diazonium salts from acetanilides [28,29] and their reactivity in Pd-catalyzed CÀC bond-forming reactions. [30][31][32][33][34] Diazonium salts have first been used in Pd-catalyzed coupling reactions more than thirty years ago [35] and their synthetic utility has recently been described in excellent reviews.…”