Abstract
We reported an efficient one-pot two-step synthesis of 3-(tert-butyl)-N-(4-methoxybenzyl)-1-methyl-1H-pyrazol-5-amine 3 in good yield by a solvent-free condensation/reduction reaction sequence starting from 3-(tert-butyl)-1-methyl-1H-pyrazol-5-amine 1 and p-methoxybenzaldehyde 2. The one-pot reductive amination proceeded by the formation in situ of the N-(5-pyrazolyl)imine 4 as key synthetic intermediate of other valuable pyrazole derivatives. This methodology is distinguished by its operational easiness, short reaction time, isolation and purification of the aldimine intermediate is not required. The structure of the synthesized N-heterocyclic amine 3 was fully characterized by FTIR-ATR, 1D and 2D NMR experiments, EIMS, and elemental analysis.
Highlights
Amines are one of the most important functional groups in organic chemistry [1]
Due to the powerful physiological activities of pyrazole derivatives and secondary amines as building blocks for the synthesis of potential druglike compound libraries and important pharmaceutical intermediates, we described the synthesis of a novel N-pyrazolyl amine 3 as a potential bioactive N-heterocycle through a simple and efficient one-pot reductive amination
In connection with the ongoing development of novel protocols for the construction of C–N bonds [20,21,22], and our current studies on the synthetic utility of N-(5-pyrazolyl)imine derivatives for the preparation of N-heterocycles of biological interest [23,24,25], we reported a one-pot two-step synthesis of 3-(tert-butyl)-N-(4-methoxybenzyl)-1-methyl-1H-pyrazol5-amine 3 through a solvent-free condensation reaction between equimolar amounts of 3-(tert-butyl)-1-methyl-1H-pyrazol-5-amine 1 and p-methoxybenzaldehyde 2 to form the N-(5-pyrazolyl)imine 4, followed by reduction with sodium borohydride in methanol at ambient temperature, as depicted in Scheme 1
Summary
Amines are one of the most important functional groups in organic chemistry [1]. In particular, N-heterocyclic amines are valuable building blocks in drug discovery and modern organic synthesis because they are key precursors in the preparation of active pharmaceutical ingredients, bioactive molecules, natural occurring products, and agrochemicals [1,2,3,4]. In connection with the ongoing development of novel protocols for the construction of C–N bonds [20,21,22], and our current studies on the synthetic utility of N-(5-pyrazolyl)imine derivatives for the preparation of N-heterocycles of biological interest [23,24,25], we reported a one-pot two-step synthesis of 3-(tert-butyl)-N-(4-methoxybenzyl)-1-methyl-1H-pyrazol5-amine 3 through a solvent-free condensation reaction between equimolar amounts of 3-(tert-butyl)-1-methyl-1H-pyrazol-5-amine 1 and p-methoxybenzaldehyde 2 to form the N-(5-pyrazolyl)imine 4, followed by reduction with sodium borohydride in methanol at ambient temperature, as depicted in Scheme 1.
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