作者:Marek Majewski、Izabella Niewczas、Nagarjuna Palyam
DOI:10.1055/s-2006-950421
日期:2006.9
Proline-catalyzed aldol addition of 2,2-dialkyl-1,3-dioxan-5-ones to aldehydes requires the presence of water, pyridinium p-toluenesulfonate or lithium chloride to proceed with high yield and high enantioselectivity. Acyclic amino acids such as alanine, phenylalanine, lysine and valine also catalyze the reaction but overall show yields and selectivities inferior to those of proline. An ester of a proline analogue shows catalytic activity in the presence of PPTS, suggesting that, in the presence of a Brønsted acid, a free carboxyl group on the catalyst might not be critical.
脯氨酸催化的 2,2-二烷基-1,3-二噁烷-5-酮与醛的醇醛加成反应需要水、对甲苯磺酸吡啶盐或氯化锂的存在,以实现高产率和高对映体选择性。非环状氨基酸,如丙氨酸、苯丙氨酸、赖氨酸和缬氨酸也能催化该反应,但总体产率和选择性逊色于脯氨酸。在存在 PPTS 的条件下,脯氨酸类似物的酯显示出催化活性,这表明在 Brønsted 酸的存在下,催化剂上的自由羧基可能并非关键。