Enantioselective deprotometalation of N,N-dialkyl ferrocenecarboxamides using metal amides
Enantioselective deprotometalation of N,N-dialkyl ferrocenecarboxamides using metal amides
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使用金属酰胺对 N,N-二烷基二茂铁甲酰胺进行对映选择性脱原金属化
DOI：
10.1039/c9nj03780b
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发表时间：
2019
影响因子：
3.3
通讯作者：
Mongin Florence
中科院分区：
文献类型：
--
作者：
Hedidi Madani;Dayaker Gandrath;Kitazawa Yu;Yoshii Tatsuya;Kimura Mutsumi;Erb William;Bentabed-Ababsa Ghenia;Chevallier Floris;Uchiyama Masanobu;Gros Philippe C.;Mongin Florence
N，N-二异丙基二茂铁甲酰胺可在低温下与丁基锂和(−)-司马汀在乙醚中对映体选择性脱金属。有兴趣的是确定可以允许具有更多活性官能团(例如酯和酮)的底物被类似地转化的条件。本文报道了由简单的手性锂酰胺(R，R)-或(S，S)-双(1-苯乙基)酰胺锂(PEALi)制成的不同的手性锂锌碱用于N，N-二异丙基二茂铁甲酰胺的不对称去质子化反应。首先，用不同的锌基原位捕捉剂截留生成的二茂铁基锂；用对映体双[1-(S)-苯乙基]酰胺锂((S)-PEALi)进行优化，得到产率为96%的2-碘衍生物和69%的ee有利于RP对映体。将该方法推广到N，N-二甲基二茂铁甲酰胺、吗啉二茂铁甲酰胺和N，N-二乙基二茂铁甲酰胺，后者的产率和对映体选择性相近。模型反应的密度泛函理论计算表明，(RP)-和(SP)-2-二硫代二茂铁甲酰胺的活化能相差很小。其次，通过改变反应温度、反应时间和碱用量，研究了R2[(S)-PEA]锌酸锌和R2[(S)-PEA]2ZnLi2(R=烷基)两种混合氨基烷基锌酸锂的反应行为。以Me_2[(S)-PEA]_2ZnLi_2为原料合成2-碘的产率最高，产率为97%，对映体的选择性为86%。
N,N-Diisopropylferrocenecarboxamide can be enantioselectively deprotometalated by combining butyllithium with (−)-sparteine in diethyl ether at low temperature. It is of interest to identify conditions that could allow substrates bearing more reactive functional groups (such as esters and ketones) to be similarly converted. We here report our efforts to use different chiral lithium–zinc bases, made from a simple chiral lithium amide, (R,R)- or (S,S)-lithium bis(1-phenylethyl)amide (PEALi), for the enantioselective deprotonation of N,N-diisopropylferrocenecarboxamide. First, different zinc-based in situ traps were employed to intercept the formed ferrocenyllithium; optimization using enantiopure lithium bis[1-(S)-phenylethyl]amide ((S)-PEALi) led to the 2-iodo derivative in 96% yield and 69% ee in favor of the RP enantiomer. The method was extended to N,N-dimethylferrocenecarboxamide, morpholinoferrocenecarboxamide and N,N-diethylferrocenecarboxamide; for the latter, similar yield and enantioselectivity were recorded. DFT calculations on a model reaction showed very small differences between the activation energies leading to (RP)- and (SP)-2-lithioferrocenecarboxamides. Next, the behavior of various mixed amino-alkyl lithium zincates of the types R2[(S)-PEA]ZnLi and R2[(S)-PEA]2ZnLi2 (R = alkyl) was studied, notably by varying the reaction temperature and time, and the amount of base. The best results were obtained with Me2[(S)-PEA]2ZnLi2, affording the 2-iodo derivative in 97% yield and 86% ee in favor of the SP enantiomer.
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