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.
We describe the first general method for the metal-free cyclopropanation of alkenes by using N-tosylhydrazones as an in situ source of diazo compounds. This new method works with a wide variety of alkenes (styrene derivatives, dienes, enynes, and electron-deficient alkenes) by using N-tosylhydrazones derived from various ketones or aldehydes (aromatic, aliphatic, enones). The reaction is performed
Pd-catalyzed cross-coupling reactions of less activated alkenyl electrophiles (for tosylates and mesylates) with tosylhydrazones: synthesis of various 1,3-dienes
作者:Poojan K. Patel、Jignesh P. Dalvadi、Kishor H. Chikhalia
DOI:10.1039/c4ra09012h
日期:——
Palladium catalyzed cross coupling reaction engaging N-tosylhydrazones of corresponding ketones as a nucleophilic coupling partner and various alkenyl tosylates and mesylates as an electrophiles for the synthesis of various alkenyl derivatives. The salient features of this reactions are (1) no stoichiometric organometallic reagents required, (2) it tolerates a wide range of functional groups, (3) easy