93097-70-2Relevant academic research and scientific papers
A Study of Grignard Reaction on 3,4-Diarylcoumarins: Part II - Effect of Substituents on Chromene Formation in Grignard Reaction of 4-(2-Hydroxy-phenyl)-3-phenylcoumarin
Sharma, Indra,Salman, M.,Koley, P. L.,Ray, Suprabhat
, p. 567 - 570 (2007/10/02)
Condensation of 2,2'-dihydroxy-4-methoxybenzophenone (1) with phenylacetic acid gives an inseparable mixture of 4-(2-acetoxyphenyl)-7-methoxy-3-phenylcoumarin (2) and 4-(2-acetoxy-4-methoxyphenyl)-3-phenylcoumarin (3).This isomeric mixture on Grignard reaction with MeMgI leads to a mixture of Z- and E-4-(2-hydroxy-4-methoxyphenyl)-4-(2'-hydroxyphenyl)-2-methyl-3-phenylbut-3-en-2-ols (4 and 5), which on acid treatment undergo cyclisation to 4-(2-hydroxyphenyl)-7-methoxy-2,2-dimethyl-3-phenylchromene (6) as the sole product.However, a mixture of 7-methoxy-3-phenyl-4-(2,4-dipropyloxyphenyl)coumarin (13) and 3-phenyl-7-propyloxy-4-(2-propyloxy-4-methoxyphenyl)coumarin (14), obtained from 2,2',4'-trihydroxy-4-methoxybenzophenone (12) and phenylacetic acid, under similar treatment with MeMgI produces a 60:40 mixture of 7-hydroxy-4-(2-hydroxy-4-methoxyphenyl)-2,2-dimethyl-3-phenylchromene (15) and 4-(2,4-dihydroxyphenyl)-7-methoxy-2,2-dimethyl-3-phenylchromene (16). 2,2'-Dihydroxy-5-methylbenzophenone (17), when subjected to a similar reaction sequence, produces a mixture of 4-(2-acetoxyphenyl)-6-methyl-3-phenylcoumarin (18) and 4-(2-acetoxy-5-methylphenyl)-3-phenylcoumarin (19), that gives rise to a 80:20 mixture of 4-(2-hydroxyphenyl)-2,2,6-trimethyl-3-phenylchromene (20) and 4-(2-hydroxy-5-methylphenyl)-2,2-dimethyl-3-phenylchromene (21).The role of substituents on the formation of isomeric mixtures of chromenes has been discussed.
