Deoxygenative radical C–C bond-forming reactions of alcohols are a long-standing challenge in synthetic chemistry, and the current methods rely on multistep procedures. Herein, we report a direct dehydroxylative radical alkylation reaction of tertiary alcohols. This new protocol shows the feasibility of generating tertiary carbon radicals from alcohols and offers an approach for the facile and precise construction of all-carbon quaternary centers. The reaction proceeds with a broad substrate scope of alcohols and activated alkenes. It can tolerate a wide range of electrophilic coupling partners, including allylic carboxylates, aryl and vinyl electrophiles, and primary alkyl chlorides/bromides, making the method complementary to the cross-coupling procedures. The method is highly selective for the alkylation of tertiary alcohols, leaving secondary/primary alcohols (benzyl alcohols included) and phenols intact. The synthetic utility of the method is highlighted by its 10-g-scale reaction and the late-stage modification of complex molecules. A combination of experiments and density functional theory calculations establishes a plausible mechanism implicating a tertiary carbon radical generated via Ti-catalyzed homolysis of the C–OH bond.

A DFT comparative mechanistic study unveils that the TBD-catalyzed reactions of amines with CO2 and hydrosilanes may either undergo a neutral mechanism or a mechanism involving free ions, depending on the polarity of the solvent. The nucleophilicity of the amines is an important factor to determine the chemoselectivities of the reactions to give formamide or aminal/N-methylated amine.

A DFT study demonstrates that titanium is capable of promoting C–N bond formation via an unconventional reductive elimination pathway featuring back-donation (REBD).

A DFT study demonstrates that methylation and formylation of amines with CO2 and hydrosilane, catalyzed by 1,3,2-diazaphospholene, are two competitive reaction channels.

A DFT study has been performed to gain insight into the formic-acid-catalyzed depolymerization of the oxidized lignin model (1 ox ) to monoaromatics, developed by Stahl et al. (Nature 2014, 515, 249–252). The conversion proceeds sequentially via formylation, elimination, and hydrolysis. Intriguingly, the elimination process exploits an unconventional mechanism different from the known ones such as E2 and E1cb. The new mechanism is characterized by passing through an intermediate stabilized by a proton-shared 3c–4e bond (HCOO⊖···H⊕···⊖OCα) and by shifting the 3c–4e bond to the 3c–4e HCOO⊖···H⊕···⊖OOCH bond in the joint leaving group that is originally a regular H-bond (HCOO–H···OOCH−). According to these characteristics, as well as the important role of the original HCOO–H···OOCH– bond, we term the mechanism as E1H-3c4e elimination. The root-cause of the E1H-3c4e elimination is that the poor leaving formate group is less competitive in stabilizing the negative charge resulted from Hβ abstraction by the HCOO– base than the nearby carbonyl group (CαO) that can utilize the negative charge to form a stabilizing 3c–4e bond with a formic acid molecule. In addition, the study characterizes versatile roles of formic acid in achieving the whole transformation, which accounts for why the HCO2H/NaCO2H medium works so elegantly for 1 ox depolymerizaion.

Directed C-H functionalization of heterocycles through an exocyclic directing group (DG) is challenging due to the interference of the endocyclic heteroatom(s). Recently, the "heteroatom problem" was circumvented with the development of the protection-free Pd-catalyzed aerobic C-H functionalization of heterocycles guided by an exocyclic CONHOMe DG. We herein provide DFT mechanistic insights to facilitate the expansion of the strategy. The transformation proceeds as follows. First, the Pd2(dba)3 precursor interacts with t-BuNC (L, one of the substrates) and O2 to form the L2Pd(II)-η(2)-O2 peroxopalladium(II) species that can selectively oxidize N-methoxy amide (e.g., PyCONHOMe) substrate, giving an active L2Pd(II)X2 (X = PyCONOMe) species and releasing H2O2. After t-BuNC ligand migratory insertion followed by a 1,3-acyl migration and association with another t-BuNC, L2Pd(II)X2 converts to a more stable C-amidinyl L2Pd(II)XX' (X' = PyCON(t-Bu)C═NOMe) species. Finally, L2Pd(II)XX' undergoes C-H activation and C-C reductive elimination, affording the product. The C-H activation is the rate-determining step. The success of the strategy has three origins: (i) the N-methoxy amide DG can be easily oxidized in situ to generate the active L2Pd(II)X2 species via the oxidase pathway, thus preventing the destructive oxygenase pathway leading to stable t-BuNCO or the O-bridged dimeric Pd(II) species. The methoxy group in this amide DG greatly facilitates the oxidase pathway, and the tautomerization of N-methoxy amide to its imidic acid tautomer makes the oxidation of the substrate even easier. (ii) The X group in L2Pd(II)X2 can serve as an internal base to promote the C-H activation via CMD (concerted metalation-deprotonation) mechanism. (iii) The strong coordination ability of t-BuNC substrate/ligand suppresses the conventional cyclopalladation pathway enabled by the coordination of an endocyclic heteroatom to the Pd-center.

Near-infrared (NIR)-emitting materials have been extensively studied due to their important applications in biosensing and bioimaging. Luminescent metal-organic frameworks (LMOFs) are a new type of highly emissive materials with strong...

Luminescent metal-organic frameworks (LMOFs) have been extensively studied for their potential applications in lighting, sensing and biomedicine-related areas due to their high porosity, unlimited structure and composition tunability. However, methodical...