N‐Tosylhydrazones as Reagents for Cross‐Coupling Reactions: A Route to Polysubstituted Olefins

Abstract

Metal‐free partner: No organometallic coupling partner is required for a Pd‐catalyzed cross‐coupling reaction that employs N‐tosylhydrazones as the nucleophilic component (see scheme; Ts=4‐toluenesulfonyl).

Pd-catalyzed coupling reactions of anhydro-aldose tosylhydrazones with aryl bromides to produce substituted exo -glycals

“…Optimal reaction conditions were sought for by applying literature conditions [25] to tosylhydrazone 1 [26][27][28] and bromobenzene (1,4-dioxane, 70 o C with 2 mol% tris(dibenzylideneacetone)dipalladium(0) (Pd 2 (dba) 3 ) catalyst in the presence of LiOtBu and XPhos, Table 1). Both short and longer reaction times resulted in moderate yields with the XPhos ligand (entries 1 and 2).…”

Coupling of N‐Tosylhydrazones with Terminal Alkynes Catalyzed by Copper(I): Synthesis of Trisubstituted Allenes

“…Notably, alkoxyl, acetyl, chloro, and trifluoromethyl groups are all tolerated under the given reaction conditions. The reaction also worked well with naphthyl alkynes (Table 2, entries 9 and 2 l, n-C 5 H 11 3 l, 54…”

Regioselective One‐Step Synthesis of Pyrazoles from Alkynes and N‐Tosylhydrazones: [3+2] Dipolar Cycloaddition/[1,5] Sigmatropic Rearrangement Cascade

“…Indeed, we and others, have shown that tosylhydrazones can be employed as a general source of diazo compounds from carbonyl compounds with almost no restriction regarding the structure of the hydrazone. [19] Taking advantage of this powerful transformation, a remarkable number of novel transition metal catalyzed [20] and transitionmetal-free [21] reactions have been reported. In this context, we report herein a new method for the regioselective preparation of 3,4,5-and 1,3,5-trisubstituted pyrazoles from readily available N-tosylhydrazones and terminal acetylenes through a…”