Additions of functionalized α-substituted allylboronates to aldehydes under the novel Lewis and Brønsted acid catalyzed manifolds
作者:Lisa Carosi、Hugo Lachance、Dennis G. Hall
DOI:10.1016/j.tetlet.2005.10.115
日期:2005.12
stereo- and chemoselectivity in the additions of four model α-substituted allylboronates to benzaldehyde was examined under the standard thermal (uncatalyzed) conditions and the novel Lewis and Brønsted acid-catalyzed conditions. With either of Sc(OTf)3 or triflic acid as catalysts, an α-ethyl allylboronate, 1a, led to a surprising inversion of stereoselectivity that can be tentatively rationalized through
在标准的热(未催化)条件和新型的路易斯和布朗斯台德酸催化的条件下,考察了向苯甲醛中添加四种模式α-取代的烯丙基硼酸酯到苯甲醛中的立体和化学选择性。使用Sc(OTf)3或三氟甲磺酸作为催化剂,α-乙基烯丙基硼酸酯1a会导致令人惊讶的立体选择性反转,可以通过未催化途径和催化途径之间的烯丙基硼化过渡态几何形状的细微差异来初步合理化。还发现α-甲硅烷基试剂的化学选择性(1c和1d可以在使用催化剂时逆转,从而提供烯丙基甲硅烷基化产物而不是由热未催化反应获得的烯丙基硼化产物。