Carboxylates as Nucleophiles in the Enantioselective Ring-Opening of Formylcyclopropanes under Iminium Ion Catalysis
作者:Estibaliz Díaz、Efraim Reyes、Uxue Uria、Luisa Carrillo、Tomas Tejero、Pedro Merino、Jose L. Vicario
DOI:10.1002/chem.201801434
日期:2018.6.21
In this work, carboxylic acids, which are typically regarded as poor nucleophiles, are demonstrated to be competent reagents to promote the ring‐opening of formylcyclopropanes after activation of the latter through iminium ion formation. Under optimized reaction conditions, a variety of γ‐acyloxy‐substituted aldehydes can be obtained in high yields and enantioselectivities through the desymmetrization
BF(3).OEt(2) has been illuminated by successfully demonstrating the unique but highly stereoselectivereactions of hydroxy carbonyl and dicarbonyl substrates. For example, treatment of gamma-hydroxy ketone 1c with BF(3).OEt(2)/Bu(3)SnH in CH(2)Cl(2) at -78 to -40 degrees C afforded the corresponding 1, 4-diol 2c with virtually complete diastereoselection, while use of TiCl(4) as a Lewis acid under similar
These results were analyzed through the bent bond/antiperiplanar hypothesis (BBAH) orbital model to test its validity. According to the BBAH, incoming nucleophiles displace one of the two bent bonds of bicyclic oxocarbenium ion intermediates in an antiperiplanar fashion. The glycosylation stereoselectivity is then governed by the displacement of the weaker bent bond as determined by the presence of electron-withdrawing
Larson, Gerald L.; Ortiz, Margarita; Roca, Marisol Rodriguez de, Synthetic Communications, 1981, vol. 11, # 7, p. 583 - 590
作者:Larson, Gerald L.、Ortiz, Margarita、Roca, Marisol Rodriguez de
DOI:——
日期:——
Asymmetric reduction of substituted indanones and tetralones catalyzed by chiral dendrimer and its application to the synthesis of (+)-sertraline
作者:Guangyin Wang、Changwu Zheng、Gang Zhao
DOI:10.1016/j.tetasy.2006.07.010
日期:2006.8
A recoverable dendrimeric supported prolinol was used as a catalyst in the asymmetric reduction of indanones and tetralones to give separable cis and trans isomers up to 97% ee. This method was also applied in the enantio selective synthesis of the antidepressant drug (+)-sertraline. (c) 2006 Elsevier Ltd. All rights reserved.