Regioselective One-Step Synthesis of Pyrazoles from Alkynes and N-Tosylhydrazones: [3+2] Dipolar Cycloaddition/[1,5] Sigmatropic Rearrangement Cascade
作者:M. Carmen Pérez-Aguilar、Carlos Valdés
DOI:10.1002/anie.201301284
日期:2013.7.8
Rearrangement under control: A wide variety of 3,4,5‐ and 1,3,5‐trisubstituted pyrazoles can be prepared from tosylhydrazones of ketones and terminal alkynes through the title reaction sequence (see scheme; Ts=4‐toluenesulfonyl). The rearrangement, and therefore, the regioselectivity of the reaction is controlled by the nature of the substituents of the tosylhydrazone.
Decomposition of toluene-p-sulphonylhydrazones by alkali. Part II
作者:R. K. Bartlett、T. S. Stevens
DOI:10.1039/j39670001964
日期:——
Hydrazones of further mono- and especially di-carbonyl compounds have been studied. That of acetonylacetone gave hexa-2,5-diene, and that of biphenacyl gave diphenylbutadiene with much 3,6-diphenylpyridazine. Hydrazones of αβ-unsaturated aldehydes and ketones gave pyrazoles, also obtained under the same conditions from 1-toluenesulphonylpyrazolines. Hydrazones of ω-substituted acetophenones, PhCO·CH2X
leads to 2-(pyrazol-3-yl)pyridines, important structural motifs in ligands for transition metals and bioactive molecules. When the reaction is conducted with 2,6-diethynylpyridine, the important 2,6-bis(pyrazolyl)pyridines are obtained, featuring the arrangement of tridentate and also pentadentate ligands. A novel three-component version of the reaction has been designed, which involves the use of α-
Olefination of Carbonyl Compounds through Reductive Coupling of Alkenylboronic Acids and Tosylhydrazones
作者:M. Carmen Pérez-Aguilar、Carlos Valdés
DOI:10.1002/anie.201200683
日期:2012.6.11
The partners decide: The CC bond‐forming reductive cross‐coupling of alkenylboronicacids and tosylhydrazones takes place under mild reaction conditions without the need of a metal catalyst, thus giving rise to olefination‐type products (see scheme). The position of the double bond in the product is determined by the structure of the coupling partners.