Chiral Brønsted Acid Catalyzed Enantioselective Synthesis of <i>anti</i>-Homopropargyl Alcohols via Kinetic Resolution–Aldehyde Allenylboration Using Racemic Allenylboronates
作者:Andy S. Tsai、Ming Chen、William R. Roush
DOI:10.1021/ol4003459
日期:2013.4.5
A chiral phosphoric acidcatalyzedkinetic resolution/allenylboration of racemicallenylboronates with aldehydes is described. Allenylboration of aldehydes with 2.8 equiv of allenylboronate (±)-1 in the presence of 10 mol % of catalyst (R)-2 provided anti-homopropargylalcohols 3 in 83–95% yield with 9:1 to 20:1 diastereoselectivity and 73–95% ee. The catalyst enables the kinetic resolution of the
Diastereo- and Enantioselective Synthesis of (<i>E</i>)-2-Methyl-1,2-<i>syn</i>- and (<i>E</i>)-2-Methyl-1,2-<i>anti</i>-3-pentenediols via Allenylboronate Kinetic Resolution with (<sup><i>d</i></sup>Ipc)<sub>2</sub>BH and Aldehyde Allylboration
作者:Jeng-Liang Han、Ming Chen、William R. Roush
DOI:10.1021/ol3010968
日期:2012.6.15
Enantioselective hydroboration of racemic allenylboronate (+/-)-1 with 0.48 equiv of ((d)Ipc)(2)BH at -25 degrees C proceeds with efficient kinetic resolution and provides allylborane (R)-Z-4. When heated to 95 degrees C, allylborane (R)-Z-4 isomerizes to the thermodynamically more stable allylborane isomer (S)-E-7. Subsequent allylboration of aldehydes with (R)-Z-4 or (S)-E-7 at -78 degrees C followed by oxidative workup provides 1,2-syn- or 1,2-anti-diols, 2 or 3, respectively, in 87-94% ee.