alcohols via an allenyl addition to indoline-2,3-diones. Origins of the high enantioselectivity in chiral BINOL-catalyzed allylboration of isatins were examined by DFT calculations. A hypothetical scenario suggested a crucial internal hydrogen bonding between the amide group (C═O···H–O) and the ethylene hydroxyl of the transient chiral mixed boronate ester, generating a rigid and stabilized system that favors
Efficient and straightforward preparation of a building block for (−)-teubrevin G synthesis via chemically diversed oriented synthesis
作者:Daniel Garcia Velazquez、Rafael Luque
DOI:10.1016/j.tetlet.2011.10.112
日期:2011.12
A rapid and efficient methodology to highly functionalised molecular units well suited as scaffolds for diversity-oriented molecular construction in the synthesis of natural products is reported herein. A key macrocyclic intermediate in the synthesis of the neo-clerodane diterpene (-)-teubrevin G was successfully synthesized in a 5-step sequence in a 70% overall yield using a novel intramolecular coupling between an allylborating agent and a 1,5-dialdehyde moiety. (C) 2011 Elsevier Ltd. All rights reserved.
Asymmetric Propargylation of Ketones Using Allenylboronates Catalyzed by Chiral Biphenols
作者:David S. Barnett、Scott E. Schaus
DOI:10.1021/ol201535b
日期:2011.8.5
Chiralbiphenolscatalyze the enantioselective asymmetric propargylation of ketones using allenylboronates. The reaction uses 10 mol % of 3,3′-Br2-BINOL as the catalyst and allenyldioxoborolane as the nucleophile, in the absence of solvent, and under microwave irradiation to afford the homopropargylic alcohol. The reaction products are obtained in good yields (60–98%) and high enantiomeric ratios (3:1–99:1)