Practical Synthesis of 4,4,4-Trifluorocrotonaldehyde: A Versatile Precursor for the Enantioselective Formation of Trifluoromethylated Stereogenic Centers via Organocatalytic 1,4-Additions.

The practical synthesis of 4,4,4-trifluorocrotonaldehyde (1) and its application to enantioselective 1,4-additions are described. The organocatalytic 1,4-addition of 1 with several nucleophiles such as heteroaromatics, alkylthiols and aldoximes afforded the corresponding products, each bearing a trifluoromethylated stereogenic center with high optical purity. A resulting product was converted into an MAO-A inhibitor, befloxatone.