An efficient copper‐catalyzed α‐aminoxylation of ketones with 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO) is presented for the synthesis of 2‐aryloxy‐1‐aryl‐2‐(2,2,6,6‐tetramethylpiperidin‐1‐yloxy)ethanones in moderate to excellent yields. It is noteworthy that the copper/iron (Cu/Fe) catalyst can be recovered and reused several times with high catalytic reactivity.
The results from structure studies on 6a-thiathiophthenes show that different substituent groups perturb the bonding in the three-sulphur sequence to different degrees. Both equal and unequal S? S bonds occur in symmetrically as well as in unsymmetrically substituted derivatives. The specific effect of methyl and phenyl substituents on the sulphur-sulphur bonding may be described by the results from CNDO/2 calculations on mono-methyl and mono-phenyl substituted 6a-thiathiophthenes. Molecular packing and intermolecular close contacts also seem to affect the S? S bonding. The structures of equally substituted 6a-thiathiophthene analogues with and show, when compared with the equivalent 6a-thiathiophthene, that and cause a pronounced change in the S? S bonding, while the perturbation caused by is negligible. In symmetrical 6a-thiathiophthene analogues with and , the average bond length in the linear three-atom sequence is 9 – 12% longer than the respective single bond. 相似文献
Carbamoyl fluorides are formed in reactions of hydroxylamines with difluorocarbene generated from sodium bromodifluoroacetate as readily available and non‐toxic carbene precursor. The process shows a high functional group tolerance, and the reaction path has been rationalized by computational calculations.
Visible light and eosin Y catalyze the synthesis of vinyl sulfones from aryl sulfinates and alkenes by a photoredox process. The reaction scope is broad in aryl sulfinates and alkenes and the general and simple procedure provides a metal‐free alternative for the synthesis of synthetically valuable vinyl sulfones.
Palladium catalyzed conversion of 1‐(2‐aminophenyl)‐propargyl alcohols to 3‐alkynyl quinolines is realized via a cascade that involves aminopalladation, oxidative coupling with alkynes and dehydration. The method is shown to have a broad substrate scope with respect to propargyl alcohols as well as alkynes. Vinyl ketones as coupling partners in the same reaction afforded 3‐alkenyl quinolines with equal ease.
Herein a practical and efficient protocol for preparing a range of aminoisoquinolines is reported. Various aminoisoquinolines were prepared in moderate to good yields from the corresponding 2‐methylbenzonitriles and benzonitriles upon treatment with potassium tert‐butoxide.
Potassium hydroxide‐catalyzed hydrosilylation exhibits excellent activity and chemoselectivity for the reduction of cyclic imides under mild reaction conditions. The chemoselectivity of the reduction system may be readily tuned by changing the identity and stoichiometry of the hydrosilanes: a polymethylhydrosiloxane (PMHS)/potassium hydroxide reduction system resulted in the reduction of various cyclic imides to the corresponding ω‐hydroxylactams in 70–94% yield, while the diphenylsilane (Ph2SiH2)/potassium hydroxide reduction system selectively afforded the aryl lactams in 33–95% yield. These catalytic protocols tolerate diverse functional groups and are easy to scale up.
A metal‐free vinylic carbon‐hydrogen bond thiolation has been developed. Under the catalysis of iodine (10 mol%), the cyclization of α‐alkenoyl ketene dithioacetals afforded a broad range of polyfunctionalized 2‐methylene‐3‐thiophenones in good selectivity with moderate to excellent yields via tandem iodocyclization and dehydroiodination. The synthetic strategy can also be extended to the cyclization of ortho‐methylthiophenyl vinyl ketones leading to 2‐methylene‐3‐benzothiophenones.
Benzofuran derivatives can be synthesized through the sequential Michael addition and cyclization of 1,3‐dicarbonyl compounds with 1,4‐benzoquinones. However, ketones are rarely used in this reaction because of their low nucleophilicities. In this study, this problem was solved by utilizing triethyl orthoformate, which enabled the formation of a vinyl ethyl ether as an additive. As a result, the nucleophilicity of ketones increased. Many important 5‐hydroxybenzofuran derivatives, which were not readily available by synthesis in the past, were also prepared via these newly established reactions.
Two experimental approaches to the synthesis of a scarcely reported biologically active thienoisoquinoline system are demonstrated. A 5‐step linear synthesis employing a palladium‐catalyzed decarboxylative cross‐coupling and functionalization sequence allowed for the preparation of a diverse range of substituted thienoisoquinoline systems. Alternatively the palladium‐catalyzed decarboxylative cross‐coupling and C H activation steps can be telescoped to produce a one‐pot reaction sequence that provides efficient access to aryl‐substituted thienoisoquinolines.
