The AZARYPHOS Family of Ligands for Ambifunctional Catalysis: Syntheses and Use in Ruthenium‐Catalyzed anti‐Markovnikov Hydration of Terminal Alkynes

Abstract

The family of AZARYPHOS (aza–aryl–phosphane) phosphane ligands, containing a phosphine unit and sterically shielded nitrogen lone pairs in the ligand periphery, is introduced as a tool for developing ambifunctional catalysis by the metal center and nitrogen lone pairs in the ligand sphere. General synthetic strategies have been developed to synthesize over 25 examples of structurally diverse (6‐aryl‐2‐pyridyl)phosphanes (ARPYPHOS), (6‐alkyl‐2‐pyridyl)phosphanes (ALPYPHOS), 4,6‐disubsituted 1,3‐diazin‐2‐ylphosphanes or 1,3,5‐triazin‐2‐ylphosphanes, quinazolinylphosphanes, quinolinylphosphanes, and others. The scalable syntheses proceed in a few steps. The incorporation of AZARYPHOS ligands (L) into complexes [RuCp(L)2(MeCN)][PF6] (Cp=cyclopentadienyl) gives catalysts for the anti‐Markovnikov hydration of terminal alkynes of the highest known activities. Electronic and steric ligand effects modulate the reaction kinetics over a range of two orders of magnitude. These results highlight the importance of using structurally diverse ligand families in the process of developing cooperative ambifunctional catalysis by a metal and its ligand.

Heteroatoms moving protons: Synthetic and mechanistic studies of bifunctional organometallic catalysis

“…Our success in creating efficient and highly active catalysts for alkyne hydration and alkene isomerization ( Fig. 1), which both feature tert-butylated heterocycles, has spurred recent improvements from the Hintermann labs in synthesis of pyridyl halides and phosphines with tert-alkyl or 2,6-disubstituted aryl groups next to nitrogen [39][40][41]. In summary, the ability to vary catalyst structure, particularly the steric environment around the basic or coordinating nitrogen, allows one to finetune reactivity in many ways.…”

Structures, Mechanisms, and Results in Bifunctional Catalysis and Related Species Involving Proton Transfer

“…Our success in creating efficient and highly active catalysts for alkyne hydration and alkene isomerization ( Fig. 1) which both feature tert-butylated heterocycles has spurred recent improvements from the Hintermann labs in synthesis of pyridyl halides and phosphines with tert-alkyl or 2,6-disubstituted aryl groups next to nitrogen [27,47,48]. In summary, the ability to vary catalyst structure, particularly the steric environment around the basic or coordinating nitrogen, allows one to fine-tune reactivity in many ways.…”

Facile Synthesis of Phosphaamidines and Phosphaamidinates using Nitrilium Ions as an Imine Synthon

“…[10] The archetypical P,N ligand 2-pyridyldiphenylphosphane (B) has found widespread application in coordination chemistry and catalysis [10c, 11] in spite of its structurally limited N-donor site. [12] Iminophosphanes (i.e., phosphaamidines C), in contrast, offer an easily tunable imine fragment which allows facile steering of the steric and electronic properties of the ligand, but they are difficult to access. So far, only four examples were prepared by reacting an imidoyl chloride [13,14] with alkali-metal phosphides [15] or silylphosphanes.…”