59000-96-3Relevant academic research and scientific papers
Photochromic Heterocyclic Fulgides. Part 6. Base-catalysed Cyclizations of 1-(2,5-Dimethyl-3-furyl and 2,5-Dimethyl-3-thienyl)ethylidene(isopropylidene)succinic Anhydrides and Related Compounds
Bowden, Sean L.,Harris, Stuart A.,Heller, Harry G.,Hewlins, Michael J. E.
, p. 725 - 728 (2007/10/02)
The title fulgides 1a and 3a (X = O or S) rearrange in boiling pyridine to yield deep red cis-8,8a-dihydro-2,4,7,8a-tetramethyl-7H-cyclohepta-furan and -thiophene-5,6-dicarboxylic anhydrides 6a (X = O or S) respectively.The corresponding 2-thienyl fulgide 8 undergoes a similar rearrangement but with a subsequent 1,5-shift of its 3-hydrogen to give the colourless cis-5,6-dihydro-5,8-dimethyl-4H-cycloheptathiophene-6,7-dicarboxylic anhydride 11.The 3-thienylfulgide 1d (X = S) undergoes a similar rearrangement to yield the colourless trans-7,8-dihydro-4,7-dimethyl-6H-cycloheptathiophene-5,6-dicarboxylic anhydride 7. 3-Methyl-5,5-diphenylcyclohepta-1(7),2-diene-1,2-dicarboxylic anhydride 13 is obtained in an analogous reaction from (E)-3,3-diphenylallylidene(isopropylidene)succinic anhydride 12.Structural assignments are based on NMR studies.The mechanistic implications of the reactions are discussed.
