High Yielding, One-Pot Synthesis of Bis(1H-indazol-1-yl)methane Catalyzed by 3d-Metal Salts.

Natalie M Lind,Natalie S Joe,Brian S Newell,Aimee M Morris

doi:10.3390/reactions3010005

Abstract

Synthetic access to poly(indazolyl)methanes has limited their study despite their structural similarity to the highly investigated chelating poly(pyrazolyl)methanes and their potentially important indazole moiety. Herein is presented a high yielding, one-pot synthesis for the 3d-metal catalyzed formation of bis(1H-indazol-1-yl)methane from 1H-indazole utilizing dimethylsulfoxide as the methylene source. Complete characterization of bis(1H-indazol-1-yl)methane is given with 1H and 13C NMR, UV/Vis, FTIR, high resolution mass spectrometry and for the first time, single crystal X-ray diffraction. This simple, inexpensive pathway to yield exclusively bis(1H-indazol-1-yl)methane provides synthetic access to further investigate the coordination and potential applications of the family of bis(indazolyl)methanes.

Highlights

Bis(1H-indazol-1-yl)methanePoly(1H-pyrazol-1-yl)alkanes are a class of ligands that have been investigated due to their overall neutral charge and unique bidentate chelating capabilities through the formation of a six- or seven-membered ring in a boat conformation upon binding to a metal center [1]
1H-indazole and dimethylsulfoxide using either a comThe generalized for the optimized high yielding, one-pot syn1 mercially available
Our results indicate that a metal catalyst with Dimethyl sulfoxide (DMSO) at 175 C was necessary free catalysis is observed with

Summary

Introduction

Bis(1H-indazol-1-yl)methanePoly(1H-pyrazol-1-yl)alkanes are a class of ligands that have been investigated due to their overall neutral charge and unique bidentate chelating capabilities through the formation of a six- or seven-membered ring in a boat conformation upon binding to a metal center [1]. The first synthesis of a poly(1H-pyrazol-1-yl)methane was reported by Hückel and Chneider in 1937 [2]. In 1970, Trofimenko reported on the synthesis and coordination chemistry of a family of methane and/or pyrazole substituted bis(1H-pyrazol-1-yl)methane chelating agents, Figure 1a [3,4]. A second synthetic method using acetals of aldehydes and ketones was utilized for the preparation of a series of bis(1H-pyrazol-1-yl)methane ligands with substituted carbon linkers [4]. The preparation of poly(1H-pyrazol-1-yl)methanes utilizing multiple synthetic methods has been extensively studied and recently reviewed [3]. Recent applications of bis(1H-pyrazol-1-yl)methanes have highlighted its use in stabilizing chiral coordination complexes [5] and catalysis [6]. Related to the bis(1H-pyrazol-1yl)methane ligands, but less studied are the family of bis(1H-indazol-1-yl)methane ligands,

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Discussion

Conclusion