Pd^II‐Catalyzed Mild CH ortho Arylation and Intramolecular Amination Oriented by a Phosphinamide Group

Abstract

A novel protocol for the Pd-catalyzed ortho-arylation of aryl phosphinamide with boronic acid is reported. By using phosphinamide as a new directing group, the reaction proceeds efficiently under mild conditions at 408C. Mechanistic studies reveal that the reaction proceeds via a PdII to Pd0 cycle. The phosphinamide group is also shown to be an effective orienting group for direct C-H amination.

Rhodium(III)‐Catalyzed Enantiotopic C−H Activation Enables Access to P‐Chiral Cyclic Phosphinamides

“…[8e-g] Chang et al disclosed am oderately enantioselective Ir III -catalyzed CÀH amidation, [8i] and Han et al showed ah ighly selective Pd IIcatalyzed C À Harylation of phosphinamides with aryl boronic acids. [8h] Because of their ability to act as directing groups for CÀHfunctionalizations [16] as well as because of their synthetic utility,phosphinamides 1 represent avaluable substrate class for our envisioned enantioselective Rh III process.Herein, we report ah ighly enantioselective access to cyclic phosphinamides 4 possessing ac hiral phosphorus(V) atom.…”

“…[ Other solvents such as toluene,a cetonitrile,o rd ioxane caused astrong reduction in conversion, yield, and selectivity (entries [14][15][16].…”

Pd‐Catalyzed Synthesis of Other Heteroatom‐Containing Heterocycles

“…A novel protocol for the Pd-catalyzed ortho-arylation of aryl phosphinamide with boronic acid is reported by Han and coworkers (Scheme 4.31) [44]. By using Pd(OAc) 2 (10 mol%) BQ (10 mol%) Ag 2 CO 3 (1.5 equiv.)…”

Mild metal-catalyzed C–H activation: examples and concepts

“…It could be reasonably speculated, however, that the weakly coordinating amide DG permits facile C-H bond cleavage and the resulting Ru-or Pd-based metalacyclic intermediates are Inspired by the potential of the amide DG bearing an electron deficient aromatic substituent, Han and collaborators hypothesized that the installation of such a coordinating moiety could enable the direct functionalization of arylphosphine derivatives. 67 As expected, the desired direct arylation could be achieved using arylboronic acid derivatives as coupling partners. Remarkably, among five different amide DGs tested, only the electron poor moiety CONHC 6 F 5 led to conversion of the starting material at 40 1C.…”

“…This species can also be used as the active catalyst. 67 Also exploring the strategy of improving a catalytic system by tuning the properties of DGs, Gaunt and co-workers became interested in the use of imine moieties. 69 They hypothesized that the less electron withdrawing character of this auxiliary, compared to analogous carbonyl groups, would lower the electron deficiency of an aromatic ring and hence enable cyclometalation under mild reaction conditions.…”