Dimethylformamide → 2-carboxy-5-oxo-5H-dibenzo[a,d]cycloheptene

Reaction equation

[N+](=C)=[N-].BrN1C(=[O:10])CCC1=O.CN(C)[CH:14]=[O:15].[C:17]1([C:26]2[CH2:34][CH2:33][CH2:32][CH2:31][CH2:30][CH2:29][CH2:28][CH:27]=2)[CH2:25][CH2:24][CH2:23][CH2:22]CCNN=1.CN(C)[CH:37]=[O:38]>>[O:38]=[C:37]1[C:27]2[CH:28]=[CH:29][C:30]([C:14]([OH:15])=[O:10])=[CH:31][C:32]=2[CH:33]=[CH:34][C:26]2[CH:17]=[CH:25][CH:24]=[CH:23][C:22]1=2

Participants

Reactant 4

HCID 6228Dimethylformamide

HCID 9550Diazomethane

HCID 67184N-bromobutanimide

HCID 86734972Dimethylformamide diazabicyclononene

Product 1

HCID 125630012-carboxy-5-oxo-5H-dibenzo[a,d]cycloheptene

Procedure

5-Oxo-5H-dibenzo[a,d]cycloheptene-2-carboxylic acid is prepared by esterifying 2-methylterephthalic acid with methanol, in the presence of acid catalyst, to afford the corresponding dimethyl ester which, in turn, is reacted with N-bromosuccinimide to afford 2-bromomethylterephthalic acid dimethyl ester. This diester is reacted with triphenylphosphine to afford 2,5-bis(carbomethoxy)benzyltriphenyl phosphonium bromide which is treated with benzaldehyde and a non-nucleophilic base, such as diazabicylononene, to afford, after alkaline hydrolysis, cis and trans stilbene 2,5-dicarboxylic acid. Hydrogenation of this latter compound with hydrogen over a 5% palladium on carbon catalyst affords 2-(2-phenethyl)terephthalic acid. Treatment with polyphosphoric acid yields 5-oxo-5H-dibenzo[a,d]cycloheptane-2-carboxylic acid which can be recystallized from aqueous dimethylformamide. 5-oxo-5H-dibenzo[a,d]cycloheptene-2-carboxylic acid is prepared by successively treating 5-oxo-5H-dibenzo[a,d]cycloheptane-2-carboxylic acid with diazomethane, N-bromosuccinimide, and dimethylformamide/diazabicyclononene, followed by base hydrolysis and acidification.