Organoboron compounds are of great importance to organic, medicinal and materials chemistry, representing key intermediates for the introduction of a wide variety of functional groups. This is best exemplified by the Suzuki-Miyaura cross-coupling. In recent years, the direct C-H borylation of arenes has become an attractive method for the synthesis of aryl boronate esters. However, this transformation is more challenging for heterocycles bearing an azinyl nitrogen atom, where the presence of the nitrogen lone pair can inhibit the reaction. This is particularly evident at the proximal C-H bond, where C-H activation often does not occur. Whilst many heterocycles have been investigated, aminopyrazoles remain underexplored. This nucleus features in an array of bioactive molecules, such as herbicides, anti-cancer, and anti-parastic drugs (Figure 1). In this presentation, we will describe a simple method for the selective C-H functionalization at both azinyl and remote C-H positions of 3- and 5- aminopyrazoles (Scheme 1).

Regioselective borylation of azinyl heterocycles

256th National Meeting (2018)

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