[3 + 2] cycloaddition and subsequent oxidative dehydrogenation between alkenes and diazo compounds: a simple and direct approach to pyrazoles using TBAI/TBHP
作者:Ying Shao、Jingjing Tong、Yanwei Zhao、Hao Zheng、Liang Ma、Meihua Ma、Xiaobing Wan
DOI:10.1039/c6ob01522k
日期:——
sequential [3 + 2] cycloaddition and oxidative dehydrogenation reactions using TBHP as the primary oxidant. In comparison with previous cases toward pyrazoles from alkenes and diazocompounds, alkenes without a pre-organized leaving group were applied in this transformation. In addition, this methodology was distinguished by its broad substrate scope, commercially available inexpensive starting materials
A facile synthesis of pyrazoles with multi-point structural diversity by 1,3-dipolar cycloaddition
作者:Kwai Ming J. Cheung、Jóhannes Reynisson、Edward McDonald
DOI:10.1016/j.tetlet.2010.09.012
日期:2010.11
We describe the synthesis of diverse pyrazoles by 1,3-dipolar cycloaddition of ethyl diazoacetate with various acetylenes in refluxing toluene. The product pyrazoles are useful starting points for preparing a diverse collection of trisubstituted pyrazole carboxamides. For aryl and heteroaryl alkynes a single product is obtained while alkyl alkynes afford a ca. 6:1 mixture of regioisomers. The observed regioselectivity for the cycloaddition step and the ease of reaction are consistent with predictions derived from computing the HOMO-LUMO energies of the reactants. (C) 2010 Published by Elsevier Ltd.
Total Syntheses of (−)-Pyrimidoblamic Acid and P-3A
作者:Adam S. Duerfeldt、Dale L. Boger
DOI:10.1021/ja412298c
日期:2014.2.5
approach is the potential it provides for the late stage divergent synthesis of modified analogsbearing deep-seated changes in either the pyrimidine cores or the highly functionalized C2 sidechain common to both natural products. The examination of the key cycloaddition reaction revealed that the inherent 1,2,3-triazine mode of cycloaddition (C4/N1 vs C5/N2) as well as the amidine regioselectivity were