A facile route to phenyl, phenylsulfanyl and phenylselanyl substituted pyrano[3,2-c]chromenes

Ring opening and ring closure reactions of chromone-3-carboxylic acid: unexpected routes to synthesize functionalized benzoxocinones and heteroannulated pyranochromenes

“…The next step is an intramolecular nucleophilic attack of ethanol at the C-2 position of the reactive γ -pyrone ring, yielding intermediate B, which underwent cyclodehydration to form the target products 17 and 18 (Figure 9). 33…”

Synthesis and Chemical Reactivity of 4‐Oxo‐4H‐1‐benzopyran‐3‐carboxaldehyde

“…Again, 69 reacted with various amides to yield 74 , 69 , 70 , and 72 , respectively. 74 can also be synthesized under microwave irradiation in moderate to good yield (Scheme ).…”

Synthesis, antifungal activity and semi-empirical AM1-MO calculations of some new 4-oxo-4H-chromene derivatives

“…These compounds possess a highly polarized C2-C3 -bond and their reactions with dinucleophiles start predominantly from the attack of the unsubstituted C-2 atom (1,4-addition) and are accompanied by pyrone ring opening to form the -dicarbonyl intermediate capable of undergoing intramolecular heterocyclizations [7,8]. In continuation to our interest in the chemistry of 4-oxo-4H-chromene-3carbaldehydes ring system [9][10][11][12][13][14], owing to its considerable biological activities. The present work describes the preparation of new systems derived from the reaction of 4-oxo-4H-chromene-3-carbaldehydes 1a,b with primary amines 2a,e and amide/thioamide derivatives 6a-d in polar and non-polar solvents.…”