|
Abstract
|
Organophosphorus compounds have been extensively used in organic synthesis as useful reagents as well as ligands of a number of transition metal catalysts. However, there are few reactions in which organophosphorous (Ill) species work as catalysts. The a-addition of OH-acids such as phenol, 3-hvdroxybenzaldehyde, 3-hydroxy-4- methoxybenzaldehyde, 1-naphthol, 2-naphthol, 8-hydroxyquinoline, 4-hydroxy coumarine or 7-hydroxycoumarine to alkyl propiolate in the presence of triphenyiphosphine leads to O-alkylation and C-alkylation. The postulation that the phosphine induced isomerization of alkylnoates to 2,4- dienoates and addition of pronucleophiles to the 4-position of these substrares suggested the possibility of a new and unprecedented reactivity pattern for alkynoates nucleophilic addition at the a-position as shown in following Scheme as a new source of C-alkylation or O-alkylation.
|