Lactone Synthesis by Enantioselective Orthogonal Tandem Catalysis
作者:Sourabh Mishra、Aaron Aponick
DOI:10.1002/anie.201904438
日期:2019.7.8
In this work, we report enantioselective orthogonal tandem catalysis for the one pot conversion of Meldrum's acid derivatives and alkynes into δ‐lactones. This new transformation, which resembles a formal [4+2] cycloaddition with concomitant decarboxylation and loss of acetone, proceeds in high yields and excellent enantioselectivity (up to 99 % ee) over a broad substrate scope. The products are densely
在这项工作中,我们报道了对映体选择性正交串联催化作用,用于将麦德鲁姆的酸衍生物和炔烃一锅转化为δ-内酯。这种新的转化过程类似于正式的[4 + 2]环加成反应,伴随着脱羧作用和丙酮的损失,在宽的底物范围内都可以高收率和出色的对映选择性(高达99%ee)进行。产物经过密集的官能化处理,已经成熟,可以进行进一步的转化,如开环反应和还原为饱和内酯所示。结果发现,一种新的偶然形成的Ag I -Me-StackPhos复合物可有效催化高度选择性的6-内酰胺dig环化反应,完全逆转了以前在相关系统中报道的区域化学反应。更一般而言,在这项研究中,我们确定了一对可同时运行的炔烃双官能化兼容催化剂,这些催化剂可使炔烃在连续的一锅转换中既充当亲核试剂又充当亲电试剂。
Asymmetric Access to the Smallest Enolate Intermediate via Organocatalytic Activation of Acetic Ester
作者:Shaojin Chen、Lin Hao、Yuexia Zhang、Bhoopendra Tiwari、Yonggui Robin Chi
DOI:10.1021/ol402877n
日期:2013.11.15
An NHC-catalyzed activation of acetic esters to afford enolate intermediates is disclosed. The catalytically generated triazolium enolate intermediates serve as two-carbon nucleophiles that undergo highly enantioselective reactions with enones and alpha,beta-unsaturated imines to give a-unsubstituted delta-lactones and lactams, respectively.
Enantioselective Mukaiyama–Michael with 2-enoyl pyridine N-oxides catalyzed by PYBOX-DIPH-Zn(ii)-complexes at ambient temperature
作者:Subhrajit Rout、Sumit K. Ray、Vinod K. Singh
DOI:10.1039/c3ob40445e
日期:——
A chiral PYBOX-DIPH-Zn(II) catalyzedenantioselectiveMukaiyama–Michaelreaction of acyclic silylenolethers with 2-enoylpyridine N-oxides has been studied in external additive free conditions at ambient temperature. The methodology offers straightforward access to a variety of functionalized chiral 1,5-dicarbonyl compounds, which could easily be elaborated into synthetically viable pyrones via hydrolysis