5949-36-0

Fumaric acid diesters are important building blocks for organic synthesis. A class of zwitterionic organocatalysts based on an amide anion/iminium cation charge pair were found to be effective in catalyzing the isomerization of maleic acid diesters to give fumaric acid diesters. Comparison of the performance of different zwitterionic organocatalysts toward the reaction revealed that nonclassical hydrogen bonding was involved in the stabilization of the Michael adduct intermediate.

(Chemical Equation Presented) The conjugate addition of dialkylzinc reagents to allyl fumarates with subsequent Ireland-Claisen rearrangement has been accomplished yielding substituted unsymmetrical succinic acid derivatives. This one-pot reaction creates two new carbon-carbon bonds at contiguous stereogenic centers. The reaction proceeds for several alkylzinc reagents and substituted allyl fumarates. The products contain distinguishable functional handles for further manipulation.

The crystalline acids which are formally cycloadducts of cyclopentadiene and the thioaldehyde thioxoacetic acid (HO2C-CHS) have been converted into a series of esters with the alkenols CH2=CHnOH.These cycloadduct esters, 8 and 9, when subjected to flash vacuum pyrolysis (FVP) at ca. 500 deg C, liberated the corresponding alkenyl thioacetates, 10, which underwent intramolecular 'ene'reactions to give a series of thia-alkenolides having 6- to 11-membered rings.The 3-thianon-5-en-9-olide 11d has been transformed, by standard reactions, into 3-vinylhex-2-en-6-olide, 20, with removal of sulfur.The sulfoxides 28 of the cyclopentadiene adducts have been employed similarly as precursors for the corresponding thioxoacetate ester S-oxides (sulfines).Under FVP conditions, intramolecular cyclisation of the allyl 33 and the homoallyl 29 sulfines gave furan-2(5H)-one 35 and 5,6-dihydro-2-pyrone, 31, respectively.The prenyl derivative 37 gave a mixture of the simple product furan-2(5H)-one 35 and its 4-isopropenyl derivative 39.Generally, fumarate esters were formed from sulfines that had failed to cyclise.