Efficient One Pot and Chemoselective Synthesis of Polysubstituted Dihydro‐6H‐chromeno[4,3‐d]pyrazolo[1,5‐a]pyrimidin‐6‐ones via a Four‐Component Reaction

Abstract

In this research, a simple and chemoselective synthesis of highly fluorescent polysubstituted dihydro‐6H‐chromeno[4,3‐d]pyrazolo[1,5‐a]pyrimidin‐6‐ones containing one chiral stereocenter is presented by a sequential four‐component reaction of 4‐chloro‐3‐formylcoumarin, 1‐phenyl‐2‐(1,1,1‐triphenyl‐λ5‐phosphanylidene)ethan‐1‐ones (Wittig reagent), benzoylacetonitriles and hydrazine hydrate as readily available starting materials, which includes base‐mediated 1,4‐addition/aza‐Michael addition/formation of two C−N bonds. The desired products were obtained with short reaction times, easy purification (products can be purified by washing with EtOH), and medium to high yields (up to 92 %) under relatively mild reaction conditions. Molecular structures were determined by IR spectrophotometry, mass spectrometry, NMR spectroscopy, and single‐crystal X‐ray analysis.

Base-promoted synthesis of dihydrochromeno[4,3-d]pyrrolo[3,4-b]pyridines from 4-chloro-3-substituted coumarins and α-aminomaleimides

“…12 Then, with our previous knowledge, we focused on the preparation of 4-chloro-3-vinyl coumarins 2 and 4-chloro-3-formyl coumarin 2′ . 23 α-Aminomaleimide 1 (1.0 equiv.) and 4-chloro-3-vinyl coumarin 2 or 2′ (1.0 equiv.)…”

“…9 of coumarin), 7.72 (2H, d, 3 J HH = 7.9 Hz, 2CH of Ph), 7.90 (2H, d, 3 J HH = 7.9 Hz, 2CH of Ph), 9.1 (1H, dd, 3 J HH = 8.8 Hz, 2 J HH = 1.8 Hz, CH 11 of coumarin). 13 (12), 358 (53), 357 (100), 281 (12), 104 (41), 90 (23), 77 (78), 50 (13)…”

“…22 Recently, we also reported the synthesis of dihydro-6 H -chromeno[4,3- d ]pyrazolo[1,5- a ]pyrimidin-6-ones from the reaction of 4-chloro-3-vinyl coumarins and 3-amino pyrazoles under mild conditions with acceptable efficiency. 23 The possibility of a wide range of biological and physical properties makes chromenopyridines interesting synthetic targets.…”