Ru(II)-Catalyzed Asymmetric Transfer Hydrogenation of Chalcones in Water: Application to the Enantioselective Synthesis of Flavans BW683C and Tephrowatsin E
作者:Felipe C. Demidoff、Guilherme S. Caleffi、Marcella Figueiredo、Paulo R. R. Costa
DOI:10.1021/acs.joc.2c01733
日期:2022.11.4
The stereoelectronic effects of electron-donating and electron-withdrawing groups at the ortho, meta and para positions of both aromatic rings were evaluated. The 2-OH group at the B ring was well tolerated, allowing a straightforward enantioselective synthesis of two flavans through the Mitsunobu cyclization, the antiviral (S)-BW683C and the natural flavan (S)-tephrowatsin E.
oxo-tethered-Ru(II) 预催化剂通过不对称转移氢化促进以甲酸钠为氢源的查耳酮的一锅法 C=C/C=O 还原。获得了 27 种 1,3-二芳基丙-1-醇,收率(高达 96%)和对映体纯度(高达 98:2)。我们的数据表明,烯酮首先被还原为相应的二氢查尔酮(1,4-选择性),然后还原为 1,3-二芳基丙-1-醇(C=O 还原)。邻位、间位和对位给电子和吸电子基团的立体电子效应评估了两个芳环的位置。B 环上的 2-OH 基团具有良好的耐受性,允许通过 Mitsunobu 环化直接对映选择性合成两种黄烷,即抗病毒 ( S )-BW683C 和天然黄烷 ( S )-tephrowatsin E。