An Expeditious Approach for the Synthesis of β‐Carboline−Pyrazole‐Based Molecular Hybrids

Abstract

A simple and highly efficient one‐pot, metal‐free approach has been developed for the synthesis of β‐carboline−pyrazole/−pyrazoline‐based molecular hybrids. The synthesis of C1‐tethered β‐carboline−(N‐acetyl)pyrazolines was achieved by using a cyclocondensation approach, whilst β‐carboline‐substituted pyrazoles were synthesized through an I2‐mediated oxidative condensation reaction. This procedure provides easy access to biologically interesting di‐ and trisubstituted pyrazoles that are decorated with β‐carboline frameworks.

A cascade A3 coupling strategy towards the regioselective synthesis of β-carboline N-fused pyrrole derivatives with pyridine tethers

“…The study commenced with the gram scale synthesis of the natural product, Kumujian C, and its analogues 1–3 . 31 In the first phase of screening studies to find the optimal conditions, N -methyl Kumujian C ( 1 ), 5-bromo-2-aminopyridine ( E ) and phenylacetylene ( a ) were selected as model precursors towards the synthesis of the expected prototype 1aE or 1aE′ . When the reaction was conducted in the presence of CuSO 4 ·5H 2 O (20 mol%) as a catalyst in dry toluene at 100 °C for 24 h under inert conditions, a single product was obtained in 55% yield (entry 1, Table 1).…”

DABCO Mediated Sulfur Activation‐Intramolecular De‐Nitration Strategy for the Synthesis of Novel Dihydrothiochromeno[4,3‐c]pyrazoles

“…[23] TFA-assisted condensation of 2-nitroacetophenone (1) with phenylhydrazines a-h in EtOH afforded the corresponding hydrazone derivatives 1 a-h, which were transformed into 1-aryl-3-(2-nitrophenyl)-1H-pyrazole-4-carbaldehydes (2 a-h) via Vilsmeier-Haack formylation approach. [24] To achieve the synthesis of diversely substituted pyrazole fused thiochromenes; pyrazole-4-carbaldehydes 2 a-h were subjected to Claisen-Schmidt condensation [25] with aryl methyl ketones A-G to afford pyrazole C4 tethered enones linked with nitrophenyl moiety i. e. (E)-3-[3-(2-nitrophenyl)-1-aryl-1H-pyrazol-4-yl]-1-arylprop-2-en-1-ones (3) (Scheme 2). The respective enones 3 were obtained within 1-3.5 hours in excellent isolated yields (70-93%) via filtration of solid product precipitated during the course of reaction and no column chromatographic purification was required.…”

Domino Aza-Annulations of Enynyl-/(Alkynyl)aryl-acetonitriles to Access Nitrogen-Enriched Heterocycles

“…The versatility of this domino aza-annulation was planned to extend for the synthesis of triazolo­[5,1- a ]-β-carbolines (Scheme ). We were pleased to find that 2-(2-(phenylethynyl)-1 H -indol-3-yl)­acetonitrile could undergo annulation to give 5j in 67% yield. Likewise, 3-indolyl-acetonitriles, holding diverse arylethynyl groups 4-Me-phenyl, 4-Cl-phenyl, and 2-thiophenyl, were proficiently transformed to triazolo­[5,1- a ]-β-carbolines 5k – 5m in decent yields, respectively.…”