Direct Access to Aryl Bis(trifluoromethyl)carbinols from Aryl Bromides or Fluorosulfates: Palladium‐Catalyzed Carbonylation

A palladium‐catalyzed carbonylative approach for the direct conversion of (hetero)aryl bromides into their α,α‐bis(trifluoromethyl)carbinols is described, and it employs only stoichiometric amounts of carbon monoxide and trifluoromethyltrimethylsilane. In addition, aryl fluorosulfates proved highly compatible with these reaction conditions. The method is tolerant of a diverse set of functional groups, and it is adaptable to late‐stage carbon‐isotope labeling.     

Palladium‐Catalyzed Carbonylation Reactions of Aryl Halides and Related Compounds

A CO group richer : (Hetero)arenes are vital intermediates in the manufacture of agrochemicals, dyes, pharmaceuticals, and other industrial products. In the past decades transition‐metal‐catalyzed coupling reactions of aryl halides with all types of nucleophiles have been developed. This Review summarizes recent work in the area of palladium‐catalyzed carbonylation reactions of aryl halides and related compounds (see scheme).

     

Convenient Synthesis of Aryl Ferrocenyl Ketone via Palladium‐Catalyzed Carbonylation Coupling

A series of aryl ferrocenyl ketones were prepared from iodoferrocene, phenylboronic acids, and CO via palladium‐catalyzed carbonylation coupling in a short time. The procedure was efficient and convenient and avoided formation of diacylated derivatives compared with currently available Friedel–Crafts acylation methodologies.     

CuI-catalyzed Synthesis of Aryl Thiocyanates from Aryl Iodides

Aryl thiocyanates are important compounds not only for their interesting biological properties, but also because of their use as a versatile starting material for many sulfur- containing aromatic compounds, including sulfonyl cyanides, sulfonic acids, sul…     

Glycosyl Formates: Glycosylations with Neighboring-Group Participation

Protected 2-O-benzyolated glycosyl formates were synthesized in one-step from the corresponding orthoester using formic acid as the sole reagent. Glucopyranosyl, mannopyranosyl and galactopyranosyl donors were synthesized and their glycosylation properties studied using model glycosyl acceptors of varied steric bulk and reactivity. Bismuth triflate was the preferred catalyst and KPF₆ was used as an additive. The 1,2-trans-selectivities resulting from neighboring-group participation were excellent and the glycosylations were generally high-yielding.     

Synthesis of Acylphosphonates by a Palladium‐Catalyzed Phosphonocarbonylation Reaction of Aryl Iodides with Phosphites

Acylphosphonates are conveniently synthesized from aryl iodides by a palladium‐catalyzed reaction with dialkyl phosphites under an atmospheric pressure of carbon monoxide. The reaction demonstrates the first example of the use of phosphorus nucleophiles in related metal‐catalyzed carbonylation reactions.     

Copper-Catalyzed Coupling of Thiourea with Aryl Iodides:The Direct Synthesis of Aryl Thiols

A general, economical and efficient protocol for the direct copper‐catalyzed coupling of thiourea with aryl iodides is developed and it will be potentially applied in large‐scale industry as a preferred process.     

Carbonylation of Difluoroalkyl Bromides Catalyzed by Palladium

Although important progress has been made in the fluoroalkylation reactions, the transition‐metal‐catalyzed carbonylative fluoroalkylation reaction remains challenging so far. Herein, we report the first example of a Pd‐catalyzed carbonylation of difluoroalkyl bromides with (hetero)arylboronic acids under one atmosphere pressure of CO. The reaction can also be extended to the aryl potassium trifluoroborate salts. The advantages of this protocol are synthetic simplicity, broad substrate scope, and excellent functional group compatibility. The resulting difluoroalkyl ketones can serve as versatile building blocks for the synthesis of various useful fluorinated compounds.     

Nickel-Catalyzed Cross-Coupling of Ethyl Chlorofluoroacetate with Aryl Bromides

A combinatorial nickel-catalyzed monofluoroalkylation of aryl bromides with the industrial raw regent ethyl chlorofluoroacetate has been developed. The two key factors to successful conversion are the combination of nickel with readily available nitrogen and phosphine ligands and the using of a mixture of different solvents. Mechanistic investigations indicated a new zinc regent might generated in situ and be involved in the reaction process.     

Metallaphotoredox Difluoromethylation of Aryl Bromides

Herein, we report a convenient and broadly applicable strategy for the difluoromethylation of aryl bromides by metallaphotoredox catalysis. Bromodifluoromethane, a simple and commercially available alkyl halide, is harnessed as an effective source of difluoromethyl radical by silyl‐radical‐mediated halogen abstraction. The merger of this fluoroalkyl electrophile activation pathway with a dual nickel/photoredox catalytic platform enables the difluoromethylation of a diverse array of aryl and heteroaryl bromides under mild conditions. The utility of this procedure is showcased in the late‐stage functionalization of several drug analogues.     

Palladium‐Catalyzed Carbonylative Coupling of (2‐Azaaryl)methyl Anion Equivalents with (Hetero)Aryl Bromides

Conditions for the palladium‐catalyzed coupling of (2‐pyridyl)acetones with aryl bromides have been developed. Followed by an acid‐promoted deacetylation step, the desired 1‐(het)aryl‐2‐(2‐pyridyl)ethanones were obtained in good to excellent yields with high functional group tolerance. Test reactions revealed that both the addition of MgCl₂ and a specifically positioned heteroatom in the heteroaromatic ring were crucial for product formation indicating the importance of a chelated intermediate in the reaction mechanism. The reaction conditions proved suitable for a number of 5‐ and 6‐membered heteroaromatic starting materials affording all products in good yields. The utility of the obtained 1‐(het)aryl‐2‐(2‐pyridyl)ethanones was demonstrated by the straightforward synthesis of several multiaromatic derivatives in only few additional steps.     

Manganese-Catalyzed Transfer Hydrodebromination of Aryl Bromides with Ethanol

A convenient PNP pincer manganese catalyzed transfer hydrogenation of bromides to corresponding debrominated aryl compounds using ethanol as the hydrogen sources is reported. Importantly, the application of biomass-derived ethanol highlights the sustainability of the methodology. The use of 6-phenyl substituted triazine-based P^iprN⁵P^ipr manganese pincer catalyst allows for the debromination of various aryl bromides with good yields. Notably, the process also occurs with bromides derived from several classes of natural products and bioactive compounds, such as citronellol, diacetone fructose, cholesterol, and vitamin E.