137411-62-2Relevant articles and documents
Application of 3-Oxabicyclohept-6-ene-2,4-dione (Cyclobut-3-ene-1,2-dicarboxylic Anhydride) as an Acetylene Equivalent in Cycloadditions
Cadogan, J. I. G.,Cameron, Donald K.,Gosney, Ian,Tinley, Edward J.,Wyse, Stuart J.,Amaro, Alicia
, p. 2081 - 2088 (2007/10/02)
The effectiveness and limitations of dioxo-3-oxabicyclohept-6-ene-2,4-dione (cyclobut-3-ene-1,2-dicarboxylic anhydride) as an acetylene equivalent in both 1,3-dipolar and Diels-Alder cycloadditions is reported; it reacted readily with a variety of reagents, including N-benzylideneaniline N-oxide, nitrile oxides, diazomethane, cyclopentadiene, tetracyclone, anthracene, 1,2,5-triphenylphosphole 1-oxide and 1,3-diphenylisobenzofuran.The structures and stereochemistry of the adducts were deduced from their NMR data; in all cases, the sterically favoured anti-isomersare formed exclusively.The configuration of the Diels-Alder adducts are assigned as endo with the exception of that from tetracyclone (and possibly 1,3-diphenylisobenzofuran) for which an exo-structure is assumed on the basis of steric arguments.Adducts were not obtained with several other reagents; possible reasons for this lack of reactivity are discussed.When subjected to flash vacuum pyrolysis, the adducts underwent thermal fragmentation, either by retro-cleavage, or by loss of maleic anhydride to form products that are derived formally from reaction of acetylene in the cycloaddition step.A concerted pathway is proposed for the pyrolytic conversion into the 'formal acetylene cycloadduct' rather than a stepwise radical mechanism.
