Three Step Green Synthesis of Substituted Butenolides Using Copper II Oxide

Butenolides are an important groups of chemicals that have a furan ring backbone. They are found in nature in a variety of compounds, with diverse functions. The most well-known butenolide is ascorbic acid, or vitamin C. Here the synthesis of a 2,3,4,4-tetrasubstituted-but-2-ene-4-olide is reported. This three step synthesis starts with the hydration of 3-methylpentyn-3-ol using a mercury II oxide catalyst to form 3-hydroxy-3-methylpentane-2-one. The second step converts this ketone into 2-cyano-3,4-dimethylhex-2-en-4-olide; a lactone, using a Knoevenagel reaction. The final step required an Aldol condensation reaction between 2-cyano-3,4-dimethylhex-2-en-4-olide and anisaldehyde to produce the final product, 2-cyano-4-methyl-3-((1E)-2-(4-methyl-phenyl)ethenyl)-hex-2-en-4-olide. The first step was also attempted using copper II oxide instead of mercury II oxide to make this process "more green."