ZrCl₄ catalysed solvent free synthesis of coumarins

Abstract

ZrCl4 is an efficient catalyst in the Pechmann condensation of phenols with ethyl acetoacetate and propynoic acid under solvent free conditions leading to formation of coumarins in very good yields.

Factors Influencing the Regioselectivity of the Oxidation of Asymmetric Secondary Amines with Singlet Oxygen

“…Imines 2 and 3 , formed by oxidation of the benzylamine side, do not isomerize to imines 4 and 5 ,24, 27 and thus the initial ratio of photooxidation products, and hence the selectivity, can be quantified by the sum of the integrals for the respective peaks of the product pairs ( 2 + 3 and 4 + 5 ; 1.08:1.00) 28. Other solvents such as ethyl acetate, toluene, and CH 2 Cl 2 afforded the same oxidation ratio.…”

Daphnetin, a Coumarin in Genus Stellera Chamaejasme Linn: Chemistry, Bioactivity and Therapeutic Potential

“…[58] Gangadasu et al synthesized daphnetin by Brønsted acid-mediated trost-type condensation reaction using pyrogallol (II) and propynoic acid with ZrCl 4 as a catalyst (Route c). [59] Wang et al synthesized daphnetin in the presence of N, N-diethylaniline and a nitrogen atmosphere using 2,3,4-trihydroxybenzaldehyde (III) as well as ethyl (triphenylphosphoranylidene) acetate as substrates (Route d). [60] Gao et al conducted one-pot Wittig/ cyclization reaction to synthesize daphnetin by reacting 2,3,4-trihydroxybenzaldehyde (VI) as a substrate with ethyl (triphenylphosphoranylidene) acetate in N,N-diethylaniline solution under N 2 atmosphere (Route e).…”

Applications of Zirconium (IV) Compounds in Organic Synthesis

“…The classical Pechmann synthesis of these compounds involves the condensation of phenols with -ketonic esters in the presence of variety of acidic condensing agents. ZrOCl 2 ·8H 2 O [98] and ZrCl 4 [99][100][101] have been found to be efficient catalyst for the synthesis of coumarins under the Pechmann reaction conditions (Scheme 45). The electron donating group on phenol promoted the reaction while the electron withdrawing group inhibited the reaction.…”