A convenient synthesis of unsymmetrical, substituted γ-pyrones from Meldrum's acid

Synthesis and calcium channel antagonist activity of novel 1,4-dihydropyridine derivatives possessing 4-pyrone moieties

“…The starting 4-pyrones 3a, b and 5a were synthesized through cyclization of related 1,3,5-triketone derivatives under acidic conditions that is an important method for the synthesis of a variety of 4-pyrones particularly those having substituents at the 2 and 6 positions (Arimoto et al, 1990;Zawacki and Crim-mine, 1996;Tyvorskii et al, 1998;Li and Lacasse, 2002;Hobuss et al, 2005;Light and Hauser, 1960;Dorman, 1967;Harris et al, 1976). 2,6-Dimethyl-4H-pyran-4-one 5b is commercially available.…”

Synthesis of aromatic heterocycles

“…149 2-Substituted γ-pyrones have been prepared in good yield from Meldrum's acid by the sequence shown in Scheme 38. 150 An unusual coumarin synthesis from phenols and acetylenic esters has been described. 151 The reaction is carried out in formic acid with a palladium(0) catalyst, which in effect directs the acetylene to the ring position ortho to the hydroxy function.…”

Cyclic 1,3‐diones and their derivatives—As versatile reactive intermediates in the syntheses of condensed fused ring heterocyles

“…The reaction between hydrazine derivatives Substituted γ-pyrones are versatile intermediates in o rg a n i c s y n t h e s i s. These can be used as polyketide synthons useful in the preparation of spiroketal containing natural products [130] as well as cycloaddition substrates for the construction of complex polycyclic system. Zawacki and Crimmins [131] reported an eff i c i e n t general synthesis of unsymmetrical substituted γpyrones as important synthetic building blocks out of acylated Meldrum's acid and vinyl ethers. Meldrum's acid was readily acylated with various acyl chlorides in presence of pyridine in DCM medium to give acyl Meldrum's acid 3 4 2.…”