Methylenelactones syntheses in supercritical fluids

A process for preparing α-methylenelactones of Formula II comprising heating lactones of Formula I and formaldehyde in a supercritical fluid in the presence of a catalyst:

• 3
• wherein,
• n=1-11;
• R1, R2, R3 and R4 taken independently are selected from the group consisting of hydrogen, hydrocarbyl or substituted hydrocarbyl, C1-C18 unsubstituted or substituted alkyl, unsubstituted or substituted alkenyl, unsubstituted or substituted cycloalkyl, unsubstituted or substituted cycloalkyl containing at least one heteroatom unsubstituted or substituted aromatic ring, and unsubstituted or substituted aromatic ring containing at least one heteroatom;
• and any two of R1, R2, R3 and R4 together can optionally form a ring.