nanofibers obtained from wood pulp by TEMPO-mediated oxidation acted as a chiral enhancer in direct aldol reactions of 4-nitrobenzaldehyde and cyclopentanone with (S)-proline as an organocatalyst. Surprisingly, catalytically inactive TEMPO-oxidized cellulose nanofibers enriched the (R,R)-enantiomer in this reaction, affording 89% ee in the syn form with a very high yield (99%). Conversely, nanocellulose-free
通过
TEMPO 介导的氧化从木浆中获得的
纤维素纳米纤维在 4-硝基
苯甲醛和
环戊酮与 ( S )-脯
氨酸作为有机催化剂的直接羟醛反应中充当手性增强剂。令人惊讶的是,催化失活的
TEMPO 氧化
纤维素纳米纤维在该反应中富集了 ( R , R )-对映异构体,以非常高的产率 (99%)提供了 89% 的顺式ee。相反,无纳米
纤维素 ( S )-脯
氨酸催化导致选择性差 (64% ee, syn形式),产率低(18%)。在疏
水结晶面上带有规则排列的手性碳的纳米
纤维素固体表面上发生的绿色有机催化将为界面催化的不对称合成策略提供新的见解。