An efficient and practical method for the construction of 2-aryl- and 2-alkyl-substituted benzothiazoles via a copper-catalyzed redox condensation process between benzothiazoles and aldehydes or ...benzylic alcohols has been developed. The reaction proceeded under mild reaction conditions using environmentally benign tert-butyl hydroperoxide (TBHP) as the oxidant. A reaction mechanism involving the ring-opening of benzothiazoles initiated by the attack of acyl radical on the thiazole ring and intramolecular condensation is proposed based on the isolation of an anilide disulfide intermediate.
Reported herein is the identification of a new methodology for the dibromination of benzylic diols. This method proceeds in moderate to good yields for a wide variety of electron-deficient, ...electron-neutral, and electron-rich aromatic substrates. Moreover, the reagent, 1,3-dibromo-5,5-dimethylhydantoin, and the solvent, tetrahydrofuran, are substantially more environmentally benign than traditional solvents and reagents used for bromination. The utility of this methodology was demonstrated in the high-yielding synthesis of a key intermediate in the synthesis of omeprazole.
The catalytic activity of copper-manganese (CuMn2) mixed oxide nanoparticles (Cu/Mn=1:2) has been studied for the selective oxidation of benzylic alcohols to the corresponding aldehydes using ...molecular oxygen as an oxidizing agent. The CuMn2 mixed oxide showed excellent catalytic activity for the oxidation of benzylic alcohols to the corresponding aldehydes with high selectivity (>99%). The complete conversion (100%) of all the benzylic alcohols to the corresponding aldehydes is achieved within a short reaction period at 102°C. The catalytic performance is obtained to be dependent on the electronic and steric effects of the substituents present on the phenyl ring. Electron withdrawing and bulky groups attached to the phenyl ring required longer reaction time for a complete conversion of the benzylic alcohols.
A convenient and efficient method for the synthesis of polysubstituted indenes has been developed by the iron(III) trichloride‐catalyzed tandem mono‐ and dibenzylation/cyclization reactions of ...benzylic alcohols with alkynes. This method is featured with the easily available starting materials, cheap catalyst, simple manipulation and mild conditions.
An efficient I2-mediated approach to the synthesis of disubstituted indenones from readily available 2-alkynylbenzyl alcohols in the presence of H2O has been developed. These results are different ...from the known iodocyclization reactions in which O-containing heterocycles are obtained.
The direct benzylation of 1,3-dicarbonyl compounds and 4-hydroxycoumarin with a wide variety of benzylic alcohols was achieved using trimethylsilyl trifluoromethanesulfonate as an efficient catalyst. ...The reaction proceeded under very mild conditions at room temperature providing the desired products in good to excellent yields.
Electron rich (R
=
MeO, Me) benzylic alcohols or acetates serve as electrophilic reaction partners in the Bi(III)-catalyzed reaction with silyl enol ethers or hydrosilanes.
The direct alkylation of ...silyl enol ethers with
para-methoxybenzylic alcohols or their corresponding acetates was efficiently catalyzed by Bi(OTf)
3 in CH
3NO
2 as the solvent. The reaction provided the α-benzylated carbonyl compounds in high yields after short reaction times using 1–2.5
mol
% of the catalyst. Benzylic acetates other than
para-methoxybenzylic acetates also underwent the reaction. High facial diastereoselectivities were observed with acetates derived from chiral α-branched
para-methoxybenzylic alcohols. In addition, a catalytic reduction with Et
3SiH as the reducing agent is reported.
N-Alkylation of tosylhydrazones in the presence of an acid catalyst is described for the first time. Tris(pentafluorophenyl) borane was found to be a mild and efficient catalyst when benzylic ...alcohols were used as the alkylating agents.
An inexpensive catalytic system consisting of vanadyl sulfate and sodium nitrite was developed for the oxidation of benzylic alcohols with molecular oxygen under mild conditions. Benzyl alcohols with ...various substitutions were efficiently converted to their corresponding aldehydes with high conversion and selectivity under 80 °C (e.g., 4‐nitrobenzyl alcohol was smoothly oxidized to 4‐nitrobenzyl aldehyde with 94% yield under 0.5 MPa of molecular oxygen). Halogen, noble metals, extra base or complicated ligands were avoided. Addition of a trace of water to this system before the reaction was crucial for the high efficiency.
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