Transition-Metal-Free Access to Primary Anilines from Boronic Acids and a Common⁺NH₂Equivalent.

Abstract

Diversely substituted anilines are prepared by treatment of functionalized arylboronic acids with a common, inexpensive source of electrophilic nitrogen (H2N-OSO3H, HSA) under basic aqueous conditions. Electron-rich substrates are found to be the most reactive by this method. However, even moderately electron-poor substrates are well tolerated under the room temperature conditions. Sterically hindered substrates appear to be equally effective compared to unhindered ones. Highly electron-deficient substrates afford product in very low yields at room temperature, but moderate to good yields are obtained at refluxing temperatures. Our method is also amenable to electrophilic amination of several common boronic acid derivatives (e.g., pinacol esters). We demonstrate that it can be combined with metal-halogen exchange reactions or a variety of directed ortho metalation protocols in a "one-pot" sequence for the synthesis of aromatic amines with unique substitution patterns. DFT studies, in combination with experimental results, suggest that the reaction occurs via base-mediated activation of HSA, followed by 1,2 aryl B-N migration. This mode of activation appears to be critical for the success of the reaction and allows, for the first time, a general, electrophilic amination of boronic acids at ambient temperature.

Pyrene Molecular Orbital Shuffle—Controlling Excited State and Redox Properties by Changing the Nature of the Frontier Orbitals

“…Compounds 4 and 8 were obtained starting from our high yielding syntheses of 2,7‐bis(Bpin)pyrene (95 %) and 2‐(Bpin)pyrene (65 %), respectively, both of which are useful entry points for the synthesis of 2‐, and 2,7‐substituted pyrene derivatives. Aminations to give the key intermediates 2‐amino ( 5 ) and 2,7‐di(amino)pyrene ( 1 ) were achieved in high yields using the metal‐free method reported by McCubbin and co‐workers . These primary amines can serve as very convenient precursors for a variety of new 2‐ and 2,7‐substituted pyrene derivatives.…”

A Theoretical Insight into the Mechanism of Cu(I)‐Catalyzed CN Coupling between Aryl Halides and Aqueous Ammonia

“…[1][2][3] The amination reactions via direct C-N bond formation between aryl halides and ammonia are strongly expected, since ammonia is one of the most abundant, least expensive, and the easy-to-handle nitrogen sources for reactions. [4] However, such preparation of primary aromatic amines traditionally needs high temperature and high pressure.…”

Metal‐ and Base‐Free Room‐Temperature Amination of Organoboronic Acids with N‐Alkyl Hydroxylamines

“…[11] Lithiated methoxyamine is an effective amination reagent for aryl and alkyl pinacol boronates. [13] Nevertheless, as pointed out by the authors,a ryl boronic acids containing N-acyl or carbonyl groups,orthose with unprotected Natoms (e.g.,i ndoles) or Satoms,a re not suitable substrates.M oreover, this reaction gives primary anilines as the products,and thus cannot be used to build up molecular complexity.M ost recently,t he conversion of BAsi nto diaryl amines was reported. [13] Nevertheless, as pointed out by the authors,a ryl boronic acids containing N-acyl or carbonyl groups,orthose with unprotected Natoms (e.g.,i ndoles) or Satoms,a re not suitable substrates.M oreover, this reaction gives primary anilines as the products,and thus cannot be used to build up molecular complexity.M ost recently,t he conversion of BAsi nto diaryl amines was reported.…”