Denmark Scott E, Fan Yu
Roger Adams Laboratory, Department of Chemistry, University of Illinois, Urbana, Illinois 61801, USA.
J Am Chem Soc. 2002 Apr 24;124(16):4233-5. doi: 10.1021/ja025670e.
Catalytic, enantioselective additions of a trichlorosilyl ketene acetal to ketones have been demonstrated. The trichlorosilyl enolate of methyl acetate undergoes a rapid and high-yielding aldol addition to a wide range of ketones (aromatic, olefinic, acetylenic, aliphatic) in the presence of a catalytic amount of pyridine N-oxide. Moreover, in the presence of a catalytic amount (10 mol %) of a chiral bispyridine bis N-oxide (possessing both axial and central chiral elements) the aldol addition takes place again in excellent yield and with good stereoselectivity. The enantioselectivities of the additions are highly variable (7-86% ee) and are strongly dependent on the structure of the ketone acceptor. Aromatic methyl ketones gave the highest selectivity, whereas olefinic ketones were the least selective.
已证明三氯甲硅烷基烯酮缩醛对酮的催化对映选择性加成反应。在催化量的吡啶N - 氧化物存在下，乙酸甲酯的三氯甲硅烷基烯醇化物能快速且高产率地与多种酮（芳香族、烯烃类、炔烃类、脂肪族）发生羟醛加成反应。此外，在催化量（10 mol%）的手性双吡啶双N - 氧化物（同时具有轴向和中心手性元素）存在下，羟醛加成反应再次以优异的产率和良好的立体选择性进行。加成反应的对映选择性变化很大（对映体过量值为7 - 86%），并且强烈依赖于酮受体的结构。芳香族甲基酮的选择性最高，而烯烃类酮的选择性最低。
