Rapid and diverse route to natural product-like biaryl ether containing macrocycles

Formal dual C(sp2)–H cross-dehydrogenative C–O bond formation to construct highly functionalized diaryl ethers with O2

A formal dual C(sp2)–H cross-dehydrogenative C–O bond formation reaction between phenols and naphthylamine derivatives to construct diaryl ethers has been developed under mild conditions.

Synthesis of Diverse o-Arylthio-Substituted Diaryl Ethers by Direct Oxythiolation of Arynes with Diaryl Sulfoxides Involving Migratory O-Arylation

A diverse range of o-arylthio-substituted diaryl ethers has been synthesized by direct oxythiolation of arynes with diaryl sulfoxides that involves the formation of the C-O and C-S bonds followed by migratory O-arylation.

Rhodium(III)-Catalyzed Selective C-H Acetoxylation and Hydroxylation Reactions

An efficient Cp*Rh(III)-catalyzed, chelation-assisted C(sp²)-H acetoxylation and hydroxylation reaction has been developed for the first time. The reaction proceeds under mild conditions and allows for selective preparation of C-H acetoxylation and hydroxylation products, thus providing a good complement to previous C-H oxygenation reactions and expanding the field of Cp*Rh(III)-catalyzed C-H functionalizations.

Deceleration of thermal ring closure in a glass-forming mexylaminotriazine-substituted merocyanine (MC) linked to intramolecular hydrogen bonding

A new glass-forming photochromic spiropyran dye is reported, and its ring closure reaction is hindered by intramolecular hydrogen bonding.

Nickel-catalyzed reductive defunctionalization of esters and amides to aromatic hydrocarbons

In two recent studies, nickel has been used in the removal of ester and amide groups to afford aromatic hydrocarbons via one-pot reductive activation followed by tandem C–CO bond cleavage–decarbonylation. Isolation and characterization of key intermediates provide insight into this acyl C–O bond activation pathway.

Palladacycles of sulfated and selenated Schiff bases of ferrocene-carboxaldehyde as catalysts for O-arylation and Suzuki–Miyaura coupling

Palladacycles of Schiff-bases having a ferrocene core catalyze O-arylation of ArBr and Suzuki–Miyaura coupling of ArBr/Cl with a yield up to 93%.

Isocyanide-based multicomponent reactions towards cyclic constrained peptidomimetics

In the recent past, the design and synthesis of peptide mimics (peptidomimetics) has received much attention. This because they have shown in many cases enhanced pharmacological properties over their natural peptide analogues. In particular, the incorporation of cyclic constructs into peptides is of high interest as they reduce the flexibility of the peptide enhancing often affinity for a certain receptor. Moreover, these cyclic mimics force the molecule into a well-defined secondary structure. Constraint structural and conformational features are often found in biological active peptides. For the synthesis of cyclic constrained peptidomimetics usually a sequence of multiple reactions has been applied, which makes it difficult to easily introduce structural diversity necessary for fine tuning the biological activity. A promising approach to tackle this problem is the use of multicomponent reactions (MCRs), because they can introduce both structural diversity and molecular complexity in only one step. Among the MCRs, the isocyanide-based multicomponent reactions (IMCRs) are most relevant for the synthesis of peptidomimetics because they provide peptide-like products. However, these IMCRs usually give linear products and in order to obtain cyclic constrained peptidomimetics, the acyclic products have to be cyclized via additional cyclization strategies. This is possible via incorporation of bifunctional substrates into the initial IMCR. Examples of such bifunctional groups are N-protected amino acids, convertible isocyanides or MCR-components that bear an additional alkene, alkyne or azide moiety and can be cyclized via either a deprotection-cyclization strategy, a ring-closing metathesis, a 1,3-dipolar cycloaddition or even via a sequence of multiple multicomponent reactions. The sequential IMCR-cyclization reactions can afford small cyclic peptide mimics (ranging from four- to seven-membered rings), medium-sized cyclic constructs or peptidic macrocycles (>12 membered rings). This review describes the developments since 2002 of IMCRs-cyclization strategies towards a wide variety of small cyclic mimics, medium sized cyclic constructs and macrocyclic peptidomimetics.

Synthesis of highly functionalized diaryl ethers by copper-mediated O-arylation of phenols using trivalent arylbismuth reagents

Highly functionalized diaryl ethers were prepared by copper(II) acetate mediated O-arylation reaction of phenols using trivalent organobismuthanes. The reaction is performed under simple conditions and tolerates a wide diversity of functional groups on the phenol and on the organobismuth reagent. Substoichiometric amounts of catalyst can be used by performing the reaction under an oxygen atmosphere. The N-arylation of pyridones is also reported.

Palladium-catalyzed C-N and C-O bond formation of N-substituted 4-bromo-7-azaindoles with amides, amines, amino acid esters and phenols

Simple and efficient procedures for palladium-catalyzed cross-coupling reactions of N-substituted 4-bromo-7-azaindole (1H-pyrrole[2,3-b]pyridine), with amides, amines, amino acid esters and phenols through C–N and C–O bond formation have been developed. The C–N cross-coupling reaction of amides, amines and amino acid esters takes place rapidly by using the combination of Xantphos, Cs₂CO₃, dioxane and palladium catalyst precursors Pd(OAc)₂/Pd₂(dba)₃. The combination of Pd(OAc)₂, Xantphos, K₂CO₃ and dioxane was found to be crucial for the C–O cross-coupling reaction. This is the first report on coupling of amides, amino acid esters and phenols with N-protected 4-bromo-7-azaindole derivatives.

A new biarylphosphine ligand for the Pd-catalyzed synthesis of diaryl ethers under mild conditions

A new bulky biarylphosphine ligand (L8) has been developed that allows the Pd-catalyzed C-O cross-coupling of a wide range of aryl halides and phenols under milder conditions than previously possible. A direct correlation between the size of the ligand substituents in the 2', 4', and 6' positions of the nonphosphine containing ring and the reactivity of the derived catalyst system was observed. Specifically, the rate of coupling increased with the size of these substituents.