A catalyst system of the present invention may further comprise a Lewis or Bronsted acid.

To enclose a Lewis-acid metal in a polymer and enable the resultant Lewis-acid metal catalyst to be recovered while maintaining the function of the catalyst.

The present invention relates to novel cocatalysts comprising (a) a Lewis base and a hydroxy compound and (b) a Lewis acid.

By a method comprising reaction of terephthalic acid (formula (II)) with trioxane or paraformaldehyde in the presence of a Lewis acid or a mineral acid, 5-carboxyphthalide is obtained with very high purity and in high yields at mild reaction conditions.

The reaction of a diisocyanate compound containing a reduced amount of chlorine is promoted by a Lewis acid and/or a protonic acid.

The Lewis acid binds to a bidentate secondary site on the Ch1 substituent to form a Lewis acid-catalyst complex.

The activating cocatalyst is generally an aluminum compound or other Lewis acid.

In a method of performing a chemical reaction using a Lewis acid, after the reaction is complete, the Lewis acid is extracted from the reaction product in the form of an aqueous solution, followed by drying of the aqueous solution of the Lewis acid.

Oss, Good (acid-base) Lewis acid part and Lewis base part

Preferably the catalyst system comprises a Lewis acid, e.g., dibutyltin dilaurate, in combination with a Brønsted acid, e.g., sulfonic acid.

The compositions comprise equal to or less than 500 ppm of a Lewis acid.

A Lewis base is also a Brønsted–Lowry base, but a Lewis acid doesn't need to be a Brønsted–Lowry acid

NOTE: A Lewis base is also a Brønsted-Lowry base, but a Lewis acid is not necessarily also a Brønsted-Lowry acid.

A Lewis base is also a Brønsted–Lowry base, but a Lewis acid doesn't need to be a Brønsted–Lowry acid.

In some embodiments, the catalyst is a transesterification catalyst, a Lewis acid, or a Lewis base such as sodium hydroxide.