[reaction: see text] Boricacid is a highly effective catalyst for the dehydrative esterification reaction between equimolar mixtures of alpha-hydroxycarboxylic acids and alcohols. In contrast, N-methyl-4-boronopyridinium iodide (2a) is a more effective catalyst than boricacid for the similar esterification in excess alcohol. A heterogeneous catalyst, such as N-polystyrene-bound 4-boronopyridinium
The present invention relates to chain extenders, processes for their preparation and their use in the preparation of biocompatible biodegradable polyurethanes and polyurethane ureas for biomedical applications such as stents, scaffolds for tissue engineering.
The chain extenders comprise a compound of formula.(I)
US9982072B2
申请人:——
公开号:US9982072B2
公开(公告)日:2018-05-29
New boron(III)-catalyzed amide and ester condensation reactions
meta- or para-position are highly effective catalysts for the amide condensation reaction in less-polar solvents. In this paper, we report that N-alkyl-4-boronopyridinium halides are more effective catalysts than the previous ones in more polar solvents. N-Alkyl-4-boronopyridinium halides are effective not only for amide condensation between equimolar mixtures of carboxylic acids and amines but also