Synthesis of aryl-substituted naphthalenes by chemoselective Suzuki–Miyaura reactions of bromo-trifluoromethanesulfonyloxy-naphthalenes. Influence of steric and electronic parameters

Chemodivergence between Electrophiles in Cross-Coupling Reactions

Chemodivergent cross-couplings are those in which either one of two (or more) potentially reactive functional groups can be made to react based on choice of conditions. In particular, this review focuses on cross-couplings involving two different (pseudo)halides that can compete for the role of the electrophilic coupling partner. The discussion is primarily organized by pairs of electrophiles including chloride vs. triflate, bromide vs. triflate, chloride vs. tosylate, and halide vs. halide. Some common themes emerge regarding the origin of selectivity control. These include catalyst ligation state and solvent polarity or coordinating ability. However, in many cases, further systematic studies will be necessary to deconvolute the influences of metal identity, ligand, solvent, additives, nucleophilic coupling partner, and other factors on chemoselectivity.

Catalysis with Palladium(I) Dimers

Dinuclear PdI complexes have found widespread applications as diverse catalysts for a multitude of transformations. Initially their ability to function as pre-catalysts for low-coordinated Pd0 species was harnessed in cross-coupling. Such PdI dimers are inherently labile and relatively sensitive to oxygen. In recent years, more stable dinuclear PdI -PdI frameworks, which feature bench-stability and robustness towards nucleophiles as well as recoverability in reactions, were explored and shown to trigger privileged reactivities via dinuclear catalysis. This includes the predictable and substrate-independent, selective C-C and C-heteroatom bond formations of poly(pseudo)halogenated arenes as well as couplings of arenes with relatively weak nucleophiles, which would not engage in Pd0 /PdII catalysis. This Minireview highlights the use of dinuclear PdI  complexes as both pre-catalysts for the formation of highly active Pd0 and PdII -H species as well as direct dinuclear catalysts. Focus is set on the mechanistic intricacies, the speciation and the impacts on reactivity.

Selective ortho-Functionalization of Adamantylarenes Enabled by Dispersion and an Air-Stable Palladium(I) Dimer

Contrary to the general belief that Pd-catalyzed cross-coupling at sites of severe steric hindrance are disfavored, we herein show that the oxidative addition to C-Br ortho to an adamantyl group is as favored as the corresponding adamantyl-free system due to attractive dispersion forces. This enabled the development of a fully selective arylation and alkylation of C-Br ortho to an adamantyl group, even if challenged with competing non-hindered C-OTf or C-Cl sites. The method makes use of an air-stable PdI dimer and enables straightforward access to diversely substituted therapeutically important adamantylarenes in 5-30 min.

Site-Selective, Modular Diversification of Polyhalogenated Aryl Fluorosulfates (ArOSO2 F) Enabled by an Air-Stable PdI Dimer

Since 2014, the interest in aryl fluorosulfates (ArOSO2 F) as well as their implementation in powerful applications has continuously grown. In this context, the enabling capability of ArOSO2 F will strongly depend on the substitution pattern of the arene, which ultimately dictates its overall function as drug candidate, material, or bio-linker. This report showcases the modular, substrate-independent, and fully predictable, selective functionalization of polysubstituted arenes bearing C-OSO2 F, C-Br, and C-Cl sites, which makes it possible to diversify the arene in the presence of OSO2 F or utilize OSO2 F as a triflate surrogate. Sequential and triply selective arylations and alkylations were realized within minutes at room temperature, using a single and air-stable PdI dimer.

Chiral Control in Pentacoordinate Systems: The Case of Organosilicates

Chirality at the central element of pentacoordinate systems can be controlled with two identical bidentate ligands. In such cases the topological Levi-Desargues graph for all the Berry pseudorotations (BPR, max. 20) reduces to interconnected inner and outer "circles" that represent the dynamic enantiomer pair. High enough barriers of the BPR crossovers between the two circles is all what is needed to ascertain chiral integrity. This is illustrated computationally and experimentally for the organosilicates 7 and 10 that carry besides a Me (a), Et (b), Ph (c), or F (d) group two bidentate 2-(phenyl)benzo[ b]-thiophene or 2-(phenyl)naphthyl ligands, respectively. The enantiomers of tetraorganosilane precursor 9 could be separated by column chromatography. Their chiral integrity persisted on forming the silicates. CD spectra are reported for 10c. Fluoro derivative 10d is shown to have its electronegative F substituent in an equatorial position, is stable toward hydrolysis, and its enantiomers do not racemize at ambient temperatures, while those of 10c racemize slowly.

Modular Functionalization of Arenes in a Triply Selective Sequence: Rapid C(sp2 ) and C(sp3 ) Coupling of C-Br, C-OTf, and C-Cl Bonds Enabled by a Single Palladium(I) Dimer

Full control over multiple competing coupling sites would enable straightforward access to densely functionalized compound libraries. Historically, the site selection in Pd0 -catalyzed functionalizations of poly(pseudo)halogenated arenes has been unpredictable, being dependent on the employed catalyst, the reaction conditions, and the substrate itself. Building on our previous report of C-Br-selective functionalization in the presence of C-OTf and C-Cl bonds, we herein complete the sequence and demonstrate the first general arylations and alkylations of C-OTf bonds (in <10 min), followed by functionalization of the C-Cl site (in <25 min), at room temperature using the same air- and moisture-stable PdI dimer. This allowed the realization of the first general and triply selective sequential C-C coupling (in 2D and 3D space) of C-Br followed by C-OTf and then C-Cl bonds.

Palladium(I) Dimer Enabled Extremely Rapid and Chemoselective Alkylation of Aryl Bromides over Triflates and Chlorides in Air

Disclosed herein is the first general chemo- and site-selective alkylation of C-Br bonds in the presence of COTf, C-Cl and other potentially reactive functional groups, using the air-, moisture-, and thermally stable dinuclear PdI catalyst, [Pd(μ-I)PtBu3 ]2 . The bromo-selectivity is independent of the substrate and the relative positioning of the competing reaction sites, and as such fully predictable. Primary and secondary alkyl chains were introduced with extremely high speed (<5 min reaction time) at room temperature and under open-flask reaction conditions.

Rapid Room-Temperature, Chemoselective Csp2 -Csp2 Coupling of Poly(pseudo)halogenated Arenes Enabled by Palladium(I) Catalysis in Air

While chemoselectivities in Pd⁰‐catalyzed coupling reactions are frequently non‐intuitive and a result of a complex interplay of ligand/catalyst, substrate, and reaction conditions, we herein report a general method based on Pd^I that allows for an a priori predictable chemoselective Csp2 −Csp2 coupling at C−Br in preference to C−OTf and C−Cl bonds, regardless of the electronic or steric bias of the substrate. The C−C bond formations are extremely rapid (<5 min at RT) and are catalyzed by an air‐ and moisture‐stable Pd^I dimer under open‐flask conditions.

Regioselective Suzuki couplings of non-symmetric dibromobenzenes: alkenes as regiochemical control elements

The regioselective Suzuki coupling of dibromobenzenes has been investigated. The regiochemistry is high when one bromine atom is proximal to an alkene.

Synthesis of 2-Acetyl-1,4-Dimethoxynaphthalene, A Potential Intermediate for Disubstituted Naphtho[2,3,c]pyran-5,10-dione

2-Acetyl-1-hydroxynaphthalene was converted into the title compound in three steps (bromination, substitution and methylation). 1-Methoxynaphthalene on bromination, substitution and acetylation, respectively, also yielded the target compound.