Electron Donor‐Acceptor Complex Initiated Photochemical Phosphorus Arylation with Diaryliodonium Salts toward the Synthesis of Phosphine Oxides

Abstract

Arylation of amino‐, diamino‐ and triaminophosphines with aryl(mesityl)iodonium triflates under blue light irradiation followed by oxidative P−N bond cleavage in the in situ generated amino phosphonium salts under hydrolytic conditions represent a method for the synthesis of substituted arylphosphine oxides, arylphosphinic and arylphosphonic amides respectively. The proposed approach is based on using visible light as the only promoter for the C−P bond formation, accommodates a variety of functional groups, and can be applied to the late‐stage C−H functionalization of drug molecules.

Exogenous Photocatalyst-Free Aryl Radical Generation from Diaryliodonium Salts and use in Pd-Catalyzed C–H Arylation

“…Previous investigations propose electron transfer (ET) from the Lewis base to the iodonium as the dominant radical formation mechanism. [13][14][15] However, we argue that ET from the pyridine Natom to iodine is not supported based upon the kinetic data we obtained. In a mechanism where such an ET event occurs, mesomeric groups bound to the pyridine ring would exhibit a beneficial rate impact since the added electron density would support the generated pyridinium radical cation.…”

“…Years later, Karchava et al discovered that phosphines 14 and phosphinamines 15 were more efficient activators of Ar2I salts than pyrrole and underwent P-arylation to furnish phosphonium salts in excellent yields under purple LED irradiation. In these cases, aryl radical generation and recombination dominates due to radical cage effects, 16 which explains how solvent molecules encapsulating pairs of generated radicals hinder diffusion of radicals away from each other.…”

Transition Metal and Photocatalyst Free Arylation via Photoexcitable Electron Donor Acceptor Complexes:Mediation and Catalysis

“…These protocols rely on mild reaction conditions, are high yielding in regard to aryl fragments bearing functional groups of diverse electronic and steric nature, and applicable to complex substrates, generating libraries of compounds prone to subsequent functionalization. Modification of phosphonium substrates allowed us to expand the utility of our arylation strategy toward the synthesis of tertiary arylphosphines 57 [56] through a one-pot arylation-retrophospa-Michael sequence and phosphine oxides 58 [57] via a one-pot arylation-P(V) oxidative cleavage tandem.…”

Exogenous photocatalyst-free aryl radical generation from diaryliodonium salts and use in metal-catalyzed C–H arylation

“…In past works, 10,11,16 halogen bonding interactions between the LB activator and the Ar 2 I iodine atom was presented as a critical factor enabling photolytic radical release. Instead, other groups noted the in situ formation of strongly colored EDA adducts, 9,13 which enabled photoactivity.…”