
%0 Journal Article
%A Browne, NR 
%A Brown, RFC 
%A Eastwood, FW 
%A Fallon, GD 
%T The Chemistry of Ethyl 2-Ethoxycarbonyl-5,5-Diphenylpenta-2,3,4-Trienoate, a Potential Precursor of Ph2c=C=C=C=C=O
%J Australian Journal of Chemistry
%D 1987/10/01
%V 40
%N 10
%P 1675-1686
%K 
%R https://doi.org/10.1071/CH9871675
%U https://www.publish.csiro.au/paper/CH9871675 
%X The title diester , Ph2C=C=C=C( COOEt )2 (2), has been prepared by a Wittig reaction between (2-bromo-3,3-diphenylprop-2-en-1-yl) triphenylphosphonium bromide and diethyl 2-oxopropane-1,3-dioate ( mesoxalic ester). The diester (2) undergoes cyclization reactions in concentrated sulfuric acid to give diethyl 2-(3'-phenyl-1H-inden-1'-y1idene)propane-l,3-dioate (4) and triethyl 3-oxo-3',9-diphenyl-2,3-dihydrospiro[lH-fluorene-1,l'-[1H]indene]-2,2,4-tricarboxylate (6), the structure of which was determined by X-ray crystallography. The title diester (2)adds cyclopentadiene across the 2,3-C=C bond to give diethyl 3-(2',2'-diphenylethenylidene)bicyclo[2.2.l]hept-5-ene-2,2-dicarboxylate (10). Alkaline hydrolysis of diester (10) gives an unstable colourless acid and a stable yellow crypto acid shown by X-ray crystallography to be 3-(2',2'-diphenylethenyl)bicyclo[2.2.l]hepta-2,5-diene-2-carboxylic acid (12). Attempts to convert diesters (2) and acid (12) into derivatives suitable for pyrolytic generation of Ph2C=C=C=C=C=O failed; The mono-acid chloride (14) yielded a small phenylazulene fraction on pyrolysis at 780-800&#176;/0.02 mm. 
