News&Event
33.Synthesis of Catechins via Thiourea/AuCl3-Catalyzed Cycloalkylation of Aryl Epoxides
Y. X. Liu, X. Li, G. Li, Z. Xiang, J. Xiang, M. Z. Zhao, J. Chen*, Z. Yang*
A diversity-oriented approach for the synthesis of structurally diverse catechins was achieved in good yields via thiourea/AuCl3/AgOTf-catalyzed annulations of aryl epoxides under mild conditions. This new protocol provides a highly efficient entry to a library of catechins-derived natural products, notably anti-HIV agent 8-C-ascorbyl-(−)-epigallocatechin.
32.Total Synthesis of Crisamicin A
Z. T. Li, Y. X. Gao, Y. F. Tang, M. J. Dai, G. X. Wang, Z. G. Wang* and Z. Yang*
Stereoselective total synthesis of natural product crisamicin A (1) was accomplished for the first time via the Pd/TMTU-catalyzed alkoxycarbonylative annulation to generate a uniquecis-pyran-fused lactone, an intermolecular Diels−Alder reaction to construct the pyranonaphthoquinone unit, and a novel Pd−thiourea pincer complex-catalyzed homocoupling of functionalized naphthoquinones.
31.Diversity-Oriented Synthesis of Fused Pyran v-Lactones via an Efficient Pd−Thiourea-Catalyzed Alkoxycarbonylative Annulation
Z. T. Li, Y. X. Gao, Z. D. Jiao, N. Wu, D. Z. G. Wang* and Z. Yang*
We reported herein a diversity-oriented synthesis of a range of fused pyran-γ-lactones that was effected through a versatile Pd−thiourea complex-catalyzed intramolecular alkoxycarbonylative annulation.
30. Steteoselective Construction of an Unprecedented 7-8 Fused Ring System in Micrandilactone A by [3,3]-Sigmatropic Rearrangement
Y. D. Zhang, W. Ren, Y. Lan, Q. Xiao, K. Wang, J. Xu, J. H. Chen*, Z. Yang*
The 7−8 bicyclic ring system of micrandilactone A (1) with the required stereochemistry and functional groups was constructed by a Bu3Al-promoted Claisen rearrangement. Computational studies indicated that the exocyclic vinyl ether undergoes a [3,3] sigmatropic process via a chairlike transition state to afford exclusively the Z-double bond in the newly generated 8-membered ring with a high level of chirality transfer.
29.Effective Pd-Nanoparticle (PdNP)-Catalyzed Negishi Coupling Involving Alkylzinc Reagents at Room Temperature
J. Liu, Y. Deng, H. Wang, H. Zhang, G. Yu, B. Wu, H. Zhang, Q. Li, T. B. Marder*, Z. Yang*, A. W. Lei*
Pd(OAc)2 is an efficient catalyst precursor for Negishi coupling in the presence of Bu4NBr. Secondary and primary alkylzinc reagents with β-H and arylzinc reagents all reacted with aryl iodides at temperatures as low as −20 °C, giving moderate to good yields. One example of coupling between alkynylzinc reagents and aryl iodides was tested and the yield was good. Preliminary kinetic studies indicated that the process involved PdNPs as the active catalytic species.
