Synthesis of Chiral Pyrazoles: A 1,3-Dipolar Cycloaddition/[1,5] Sigmatropic Rearrangement with Stereoretentive Migration of a Stereogenic Group
作者:M. Carmen Pérez-Aguilar、Carlos Valdés
DOI:10.1002/anie.201506881
日期:2015.11.9
the obtention of chiral pyrazoles with a stereogenic group directly attached at a nitrogen atom. The cascade reaction includes decomposition of the hydrazone into a diazocompound, 1,3‐dipolarcycloaddition of the diazo compound with the alkyne, and [1,5] sigmatropic rearrangement with migration of the stereogenic group. This strategy has been successfully applied to the synthesis of structurally diverse
The Pd‐catalyzed reaction between 2,2′‐dibromobiphenyls and related systems with tosylhydrazones gives rise to new π‐extendedconjugatedpolycarbo‐ and heterocyclesthrough an autotandem process involving a cross‐coupling reaction followed by an intramolecular Heck cyclization. The reaction shows wide scope regarding both coupling partners. Cyclic and acyclic tosylhydrazones can participate in the
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.
are employed as electrophiles in the Pd-catalyzed cross-coupling with tosylhydrazones affording di-, tri-, and tetrasubstituted olefins. Fine tunning of the reaction conditions are required to accomplish the coupling successfully, including the addition of LiCl and the presence of small amounts of water. Under the optimized conditions, the reactions proceed with high yield and also high stereoselectivity