Diastereo-Face Selectivity in the Aldol Reaction of Boryl Enolate Derived from Oppolzer's Sultam.
作者:Katsuhiko ISEKI、Satoshi OISHI、Yoshiro KOBAYASHI
DOI:10.1248/cpb.44.2003
日期:——
In the Oppolzer aldol reaction, aldehyde reacts exclusively on the Si face (C(α)-Si attack) of the double bond of the boryl enolate 2 derived from (1S, 2R)-N-propionylbornane-10, 2-sultam (1), providing only 3a stereoselectively. Hexafluoroacetone (4) caused complete reversal of the diastereo-face selectivity, reacting exclusively on the Re face (C(α)-Re attack) of 2 to give only 5. Trifluoroacetaldehyde (8) and 2, 2-difluoro-5-phenylpentanal (9) caused partial reversal of the diastereo-face selectivity, giving significant amounts of unexpected and unusual syn- (12c, 13c) and anti- (12d, 13d) aldols along with the normal syn-aldol (12a, 13a). This finding was applied to the reactions of the boryl enolate with phenylglyoxal (10) and ethyl glyoxylate (11).
在 Oppolzer 羟醛反应中,醛仅在衍生自 (1S, 2R)-N-丙酰基冰片烷-10, 2-磺内酰胺 (1S, 2R)-N-丙酰基冰片烷-10, 2-磺内酰胺 (1 ),仅立体选择性地提供 3a。六氟丙酮 (4) 导致非对映面选择性完全逆转,仅在 2 的 Re 面(C(α)-Re 攻击)上反应,仅生成 5。 三氟乙醛 (8) 和 2, 2-二氟-5-苯基戊醛(9)引起非对映面选择性的部分逆转,产生大量意想不到的和不寻常的顺式(12c,13c)和反式(12d,13d)羟醛以及正常的顺式羟醛(12a,13a)。这一发现应用于硼基烯醇化物与苯基乙二醛 (10) 和乙醛酸乙酯 (11) 的反应。