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Activation parameters are reported for ClCCF3 additions to three alkenes (tetramethylethylene, cyclohexene, and 1-hexene). The results are compared to those for CCl2, CClF, and CF2. Activation enthalpies decrease as the carbene stability decreases and its electrophilicity increases, and also as alkene reactivity (degree of alkylation) increases. Activation entropies decrease in parallel with activation enthalpies, suggesting the operation of enthalpy-entropy compensation in these carbene additions. [ABSTRACT FROM AUTHOR]

An enantioselective Fnedel—Crafts alkylation/cyclization cascade reaction of l-naphthols and α,β-unsaturated aIdehydes promoted by diphenylprolinol ether has been developed. The method affords one-pot access to chiral and synthetically useful chromanes and dihydrobenzopyranes in high yields and enantioselectivities from readily available compounds. In addition, the addition/cyclization products could be afterward transformed to various natural products and biologically active derivatives. On the basis of the experimental results and the observed absolute configurations of the products, a plausible mechanism has been proposed to explain the origin of the activation and the asymmetric induction. [ABSTRACT FROM AUTHOR]

A novel RhIII-catalyzed direct alkylation of azobenzenes with allyl acetates through C-H activation and functionalization is demonstrated in which the allyl acetates serve as unique alkylation agents. The rhodium-catalyzed alkylation provides a highly efficient and atom-economic approach to a series of azo compounds. [ABSTRACT FROM AUTHOR]

A simple and efficient protocol for nickel-catalyzed regioselective C-H bond difluoroalkylation of 8-aminoquinoline scaffolds with functionalized difluoromethyl bromides was developed. The reaction has broad substrate scope and provides a facile and useful access to the corresponding C5-functionalized difluoromethylated quinolines in good to excellent yields. [ABSTRACT FROM AUTHOR]

Two chiroptical spectroscopic techniques, namely, electronic and vibrational circular dichroism (ECD and VCD), as well as NMR spectroscopy have been utilized to determine the absolute configurations and geometries of two Fráter-Seebach alkylation reaction products with long hydrocarbon chains. The experimental studies have been complemented with density functional theory calculations. Strong characteristic bisignate VCD signatures in the carbonyl stretching region have been observed for both compounds in film state. Truncated models, i.e., without the long CH2 chains, have been utilized to examine different hydrogen-bonding topologies between two monomeric moieties and to simulate the corresponding IR and VCD spectra of the dimers. In addition, the exciton coupling model has also been applied to the -C=O groups of the two monomeric moieties, which can be coupled through intermolecular hydrogen-bonding. On the basis of these simplified approaches, the absolute configurations of the compounds have been unambiguously assigned using VCD and ECD spectroscopy. Spectral simulations in the IR and UV--vis regions have also been carried out with the full dimers to validate the fitness of the truncated model. The study shows that the combination of the film VCD and ECD techniques is a relatively straightforward method to determine the absolution configurations of such synthetic compounds. [ABSTRACT FROM AUTHOR]

Direct application of benzyl alcohols (or their magnesium salts) as electrophiles in various reactions with Grignard reagents has been developed via transition metal-catalyzed sp3 C-O bond activation. Ni complex was found to be an efficient catalyst for the first direct cross coupling of benzyl alcohols with aryl/alkyl Grignard reagents, while Fe, Co, or Ni catalysts could promote the unprecedented conversion of benzyl alcohols to benzyl Grignard reagents in the presence of nhexylMgCl. These methods offer straightforward pathways to transform benzyl alcohols into a variety of functionalities. [ABSTRACT FROM AUTHOR]

A metal-free novel, simple, and highly efficient method for the direct C2-alkylation of azoles with alcohols and ethers has been developed on the basis of an oxidative C–H activation process. The dehydrogenative C–C cross-coupling reactions of α-position sp3C–H in alcohols and ethers with the 2-position sp2C–H in azoles proceeded smoothly in the presence of tert-butyl hydroperoxide (TBHP) under neat reaction conditions, which generated the corresponding products in good yields. [ABSTRACT FROM AUTHOR]