Palladium-Catalyzed C−H Activation/Intramolecular Amination Reaction: A New Route to 3-Aryl/Alkylindazoles

Abstract

A method for the catalytic C-H activation of hydrazone compounds followed by intramolecular amination is described. It requires the use of a catalytic amount of Pd(OAc)2 in the presence of Cu(OAc)2 and AgOCOCF3, which efficiently effects the cyclization to afford variously substituted indazoles. The reactions proceed under relatively mild conditions and thus tolerate a variety of functional groups, including alkoxycarbonyl and cyano groups and halogen atoms.

Copper‐Catalyzed One‐Pot Synthesis of Imidazo/Benzoimidazoquinazolinones by Sequential Ullmann‐Type Coupling and Intramolecular CH Amidation

“…[6] Traditional methods for the synthesis of N-heterocycles substituted with functional groups require the use of prefunctionalized precursors. Recently, there have been great advances in the direct functionalization of C À H bonds, [7] and some N-heterocycles (for example, benzimidazoles, [8] carbazoles, [9] indazoles, [10] N-methoxylactams, [11] and indolines [12] ) have been synthesized through CÀH activation/ CÀN bond-formation sequences, in which expensive palladium-, rhodium-, and ruthenium-based catalysts are usually required. In recent decades, there has been remarkable progress in copper-catalyzed cross-couplings with inexpensive, low-toxicity copper catalysts, and wide applications with good functional group tolerance have been investigated.…”

Synthesis of Heterocyclic Compounds through Palladium-Catalyzed C–H Cyclization Processes

“…Encouraged by the success of our C-H cyclization approach to the synthesis of N-heterocycles such as indazoles, 22) indoles, 25) and 2-quinolinones, 30,39) we became interested in whether this intramolecular C-H amination process could be extended to C-S bond formation to prepare sulfur-based heterocycles. Indeed, when we started the study, the literature contained no examples of transitionmetal-catalyzed C-S bond formation via C-H functionalization.…”

Easily Modified Directing Groups for the Palladium-Catalyzed C—H Functionalization

“…以 Pd 2 (dba) 3 为钯试剂, X-Phos 为配体, NaOBu-t 为碱, 甲苯 为溶剂, 实现了吡啶苄基上的 sp 3 -C-H 键的芳基化 [45] . 2007 年, Hiroya 等 [64] 利用苯腙中 N 与 Pd 的配位作 用活化邻位 C-H 键, 然后通过分子内胺基化反应完成 了 3-芳基咪唑环的合成(Eq. 23).…”