Unexpected Synthesis of a 5H‐chromeno[3,4‐c]pyridine Derivative from 4‐Chlorocoumarin‐3‐carbaldehyde and Malononitrile

Abstract

In the reaction of 4‐chlorocoumarin‐3‐carbaldehyde with malononitrile in the presence of piperidine, a piperidinium salt of a novel tricyclic chromeno[3,4‐c]pyridine derivative was isolated instead of the expected “tert‐amino effect” product. When hexamethyleneimine (azepane) was used as a base, the corresponding azepanium salt (same anion) was obtained. Both structures have been formulated on the basis of their spectral (IR, NMR, MS) behavior and elemental analyses. In addition, the structure of the piperidinium salt was confirmed by means of X‐ray crystallographic analysis.

A novel magnetic layered double hydroxide as potent mesoporous recyclable heterogeneous nanocatalyst for the synthesis of 1H‐chromeno[2,3‐b]pyridine‐3‐carbonitrile derivatives

“…[47] Many of synthetic methods reported for the synthesis of various fused chromene derivatives including pyrano-fused chromenes utilize one-pot MCRs using different catalytic systems such as ionic liquids, [48] Mg/La mixed metal oxides, [49] H 6 P 2 W 18 O 62 .18H 2 O, [50] thiourea dioxide, [51] and silicagrafted ionic liquid. [52] So far, many approaches reported for the synthesis of chromeno-fused compounds employ MCRs between aromatic aldehydes and different types of reagents including malononitrile, thiols, amines, naphthols, 3-phenylisoxazol-5(4H)-one, 1,1-enediamines, ethyl benzoylacetates, and aminocoumarin under different catalytic effects [53][54][55][56] As mentioned earlier, regarding the vital importance of the environmental issues, further developments of efficient environmentally green and sustainable approaches and catalysts, particularly magnetic nanocatalysts, are on rising demand. Also, as evidenced from a huge compilation of the articles in the literature over the last few decades, many synthetic chemists have focused their attention on the design of eco-friendly methods for the synthesis of heterocyclic compounds mainly due to their biological importance utilized as useful precursors in synthetic organic and medicinal chemistry.…”

“…[ 47 ] Many of synthetic methods reported for the synthesis of various fused chromene derivatives including pyrano‐fused chromenes utilize one‐pot MCRs using different catalytic systems such as ionic liquids, [ 48 ] Mg/La mixed metal oxides, [ 49 ] H 6 P 2 W 18 O 62 .18H 2 O, [ 50 ] thiourea dioxide, [ 51 ] and silica‐grafted ionic liquid. [ 52 ] So far, many approaches reported for the synthesis of chromeno‐fused compounds employ MCRs between aromatic aldehydes and different types of reagents including malononitrile, thiols, amines, naphthols, 3‐phenylisoxazol‐5(4 H )‐one, 1,1‐enediamines, ethyl benzoylacetates, and aminocoumarin under different catalytic effects [ 53–56 ]…”