Key Laboratory of Organosilicon Chemistry and Material Technology, Ministry of Education, Hangzhou Normal University, Hangzhou, People's Republic of China.
Chirality. 2011 May;23(5):397-403. doi: 10.1002/chir.20940. Epub 2011 Apr 4.
A detailed experimental investigation of an aza-Michael reaction of aniline and chalcone is presented. A series of Cinchona alkaloid-derived organocatalysts with different functional groups were prepared and used in the aza-Michael and retro-aza-Michael reaction. There was an interesting finding that a complete reversal of stereoselectivity when a benzoyl group was introduced to the cinchonine and cinchonidine. The chirality amplification vs. time proceeds in the quinine-derived organocatalyst containing silicon-based bulky group, QN-TBS, -catalyzed aza-Michael reaction under solvent-free conditions. In addition, we have demonstrated for the first time that racemization was occurred in suitable solvents under mild conditions due to retro-aza-Michael reaction of the Michael adduct of aniline with chalcone. These indicate the equilibrium of retro-aza-Michael reaction and aza-Michael reaction produce the happening of chirality amplification in aza-Michael reaction and racemization via retro-aza-Michael reaction under different conditions, which would be beneficial to the development of novel chiral catalysts for the aza-Michael reactions.
本文对苯胺和查耳酮的氮杂迈克尔加成反应进行了详细的实验研究。合成了一系列具有不同官能团的金鸡纳生物碱衍生有机催化剂，并将其用于氮杂迈克尔加成和反氮杂迈克尔加成反应。有趣的是，当在金鸡纳碱和辛可宁中引入苯甲酰基时，立体选择性发生了完全反转。在无溶剂条件下，含有硅基大位阻基团的奎宁衍生有机催化剂 QN-TBS 可以促进氮杂迈克尔加成反应，其手性放大与时间有关。此外，我们首次证明，在手性温和的条件下，由于苯胺与查耳酮的迈克尔加成物的反氮杂迈克尔加成反应，在手性合适的溶剂中会发生外消旋化。这些结果表明，在不同条件下，反氮杂迈克尔加成反应和氮杂迈克尔加成反应的平衡会导致氮杂迈克尔加成反应中的手性放大以及通过反氮杂迈克尔加成反应的外消旋化，这将有利于发展用于氮杂迈克尔加成反应的新型手性催化剂。
