Highly Selective Copper-Catalyzed Ring Expansion of Vinyl Thiiranes: Application to Synthesis of Biotin and the Heterocyclic Core of Plavix
摘要:
We report herein a new, highly selective, mild copper-catalyzed vinyl thiirane ring-expansion protocol for the formation of 2,5-dihydrothiophenes. Preliminary substrate scope and applications of this new synthetic disconnection to the formal racemic total synthesis of biotin and the synthesis of the antiplatelet blockbuster pharmaceutical agent Plavix are described.
A novel copper-catalyzed vinyl oxirane ring expansion protocol has been developed. A wide range of vinyl oxiranes can be rearranged to 2,5-dihydrofurans in excellent yields in the presence of electrophilic copper(II) acetylacetonate catalysts. Regioisomeric vinyl oxiranes can be converted to a single dihydrofuran product using these conditions. This method uses low catalyst loadings (0.5-5 mol %), has good tolerance of substitution patterns, and can be done in the absence of solvent.
N-tosyl vinylaziridines toward arynes has been demonstrated under mild and transition-metal-free conditions to yield 2-(phenanthren-9-yl)ethan-1-sulfamides in moderate to good yields. The selective synthesis of N-H and N-aryl products was accomplished using CsF in MeCN and KF/18-C-6 in 1,4-dioxane, respectively. This cascade process involves a sequential Diels-Alder reaction, ring-opening aromatization
Palladium-Catalyzed Regioselective [5 + 1] Annulation of Vinyl Aziridines/Epoxides with ClCF<sub>2</sub>COONa
作者:Dandan Zuo、Tao Zhang、Jingjing Zhao、Wen Luo、Chaojie Wang、Pan Li
DOI:10.1021/acs.orglett.2c01739
日期:2022.7.1
regioselective [5 + 1] annulation reactions of vinyl aziridines/epoxides with ClCF2COONa have been developed. Significantly, vinyl aziridines/epoxides act as heteroatom-containing five-atom synthons, and commercially available and cheap ClCF2COONa acts as the source of carbonyl serving as a difluorocarbene precursor. This protocol provides an efficient and practical method for the synthesis of δ-lactams and
Intermolecular Oxonium Ylide Mediated Synthesis of Medium-Sized Oxacycles
作者:Daniel J. Mack、Lindsay A. Batory、Jon T. Njardarson
DOI:10.1021/ol203129d
日期:2012.1.6
Detailed in this account are our efforts toward efficient oxacycle syntheses. Two complementary approaches are discussed, with both employing chemoselective allyl ether activation and rearrangement as the key step. Vinyl substituted oxiranes and oxetanes provide a single step access to dihydropyrans and tetrahydrooxepines. Oxiranes proved to be poor substrates, while oxetanes were slightly better. An alternative approach using substituted allyl ethers proved successful and addressed the limitations encountered in the ring expansions.