Direct access to N-H-aziridines from asymmetric catalytic aziridination with borate catalysts derived from vaulted binaphthol and vaulted biphenanthrol ligands
Direct access to N-H-aziridines from asymmetric catalytic aziridination with borate catalysts derived from vaulted binaphthol and vaulted biphenanthrol ligands
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DOI：
10.1021/ja069371r
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发表时间：
2007-06-06
影响因子：
15
通讯作者：
Wulff, William D.
中科院分区：
文献类型：
--
作者：
Lu, Zhenjie;Zhang, Yu;Wulff, William D.
以三苯硼酸盐和拱形双酚（VANOL）和拱形双酚（VAPOL）为配体制备手性催化剂，研究了n -二苯基甲基胺（n - dam -亚胺）与重氮乙酸乙酯的不对称催化氮化反应（AZ）。从两种配体衍生的催化剂在不对称诱导方面同样有效，但VANOL催化剂略快。使用VANOL催化剂可以达到400次的转化率，同时在氮化吡啶产品中仍然保持>= 90%的ee。该配体的收率为95%，光学纯度无损失。芳基胺的不对称诱导效果很好，虽然烷基取代亚胺的诱导效果稍低，但所有亚胺基物的光学纯度都可以通过一次结晶提高到>= 99% ee。研究了在酸性条件下对N-DAM-aziridines进行脱保护而不引起酸促环开环的方法。烷基取代和芳基取代的氮吡啶都能得到很好的收率。最后，用Boc、tosyl和Fmoc基团活化n - h -叠氮嘧啶。活化后的叠氮吡啶可以转化为-(3)-氨基酯，出乎意料的是，n - boc保护的叠氮吡啶-2-羧酸酯16b在3位顺式取代基上被发现发生了环扩张，形成顺式和反式恶唑烷酮的混合物。
The asymmetric catalytic aziridination reaction (AZ reaction) of N-dianisylmethylimines (N-DAM-imines) with ethyl diazoacetate is developed with chiral catalysts prepared from triphenylborate and both the vaulted binaphthol (VANOL) and vaulted biphenanthrol (VAPOL) ligands. Catalysts derived from both ligands were equally effective in terms of asymmetric induction, but the VANOL catalyst was slightly faster. Up to 400 turnovers could be achieved with the VANOL catalyst while still maintaining >= 90% ee in the aziridine product. The ligand could be recovered in 95% yield with no loss in optical purity. Excellent asymmetric inductions were observed with arylimines, and although slightly lower inductions were observed for alkyl-substituted imines, the optical purity of the aziridines from all of the imine substrates could be enhanced to >= 99% ee with a single crystallization. Methods were developed for deprotection of the N-DAM-aziridines under acidic conditions without causing an acid-promoted opening of the ring. Excellent yields of the N-H-aziridines could be obtained with both alkyl- and aryl-substituted aziridines. Finally, activation of the N-H-aziridines was achieved with Boc, tosyl, and Fmoc groups. The activated aziridines can be converted to beta(3)-amino esters, and unexpectedly, the N-Boc-protected aziridine-2-carboxylate 16b with a phenyl substituent in the 3-position cis to the ester group was found to undergo ring expansion to a mixture of cis- and trans-oxazolidinones.