Stereoselective Synthesis of γ-Substituted (<i>Z</i>)-Allylic Boranes via Kinetically Controlled Hydroboration of Allenes with 10-TMS-9-borabicyclo[3.3.2]decane
作者:Jeremy Kister、Amy C. DeBaillie、Ricardo Lira、William R. Roush
DOI:10.1021/ja905494c
日期:2009.10.14
Kineticallycontrolled hydroboration of allenes 8 and 14a-d with the readily accessible Soderquist borane 7, which is generated in situ from borohydride 6, constitutes a convenient and preparatively useful method for synthesis of (Z)-gamma-(substituted)allylboranes 9 and 15a-d. These allylboranes undergo highly diastereo- (> or = 90: 10) and enantioselective (typically 89-96% e.e.) allylboration reactions
Development of a double allylboration reagent targeting 1,5-syn-(E)-diols: application to the synthesis of the C(23)–C(40) fragment of tetrafibricin
作者:Philippe Nuhant、Jeremy Kister、Ricardo Lira、Achim Sorg、William R. Roush
DOI:10.1016/j.tet.2011.06.008
日期:2011.9
Interest in the synthesis of the C(23) C(40) fragment 2 of tetrafibricin prompted us to develop a new method for the synthesis of 1,5-syn-(E)-diols. Toward this end, the kinetically controlled hydroboration of allenes 6, 33, ent-39, 42, and 45 with the Soderquist borane 25R were studied. Tetrabutylammonium allenyltrifluoroborate 45 gave superior results and was utilized in a double allylboration sequence with two different aldehydes to provide the targeted 1,5-syn-(E)-diols in generally high yields (72-98%), and with high enantioselectivity (>95% ee), diastereoselectivity (dr >20:1), and (E)/(Z) selectivity (>20:1). This new method was applied to the synthesis of the C(23) C(40) fragment 2 of tetrafibricin. (C) 2011 Elsevier Ltd. All rights reserved.