Oxidative Cross-Esterification Of Dithiolanes With Alcohols Through A Cross-Dehydrogenative Coupling(CDC)/Deprotection Sequence

Ester group is one of the most important functional groups in organic chemistry, which can be widely found in natural products, pharmaceuticals and polymers. In organic synthesis, the ester group is also usually used as a mask for carboxylic acids and hydroxy group. Given the importance of esterification in organic synthesis, it is necessary to develop the highly efficient esterification which features simple experimental procedures under very mild conditions.2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) is well known as excellent oxidant that has been widely used as privileged oxidant in cross-dehydrogenative coupling (CDC). In this context, a novel direct oxidative esterification of2-aryl-1,3-dithiolanes with alcohols promoted by cuprous iodide and DDQ was developed. This simple and mild esterification was based on a C-O bond cross-dehydrogenative coupling (CDC)/deprotection sequence.1. The optimum reaction condition for this oxdative esterification was set up, there was no need for strict operation and apparatus. Equimolar mixture of1,3-dithiolanes, alcohols and water can be transformed into esters in the presence of10mol%CuI and DDQ (2.0eq.). With the best reaction condition in hand, we investigated the substrate scope and seventeen different structure esters were obtained smoothly. In addition, all those compounds were characterized by1H NMR,13C NMR, MS and UV.2. We proposed a plausible reaction mechanism for this oxidative cross-esterification of dithiolanes with alcohols. Besides, we have proved it through capturing the intermediate based on a C-O bond cross-dehydrogenative coupling (CDC) and the18O-labeling experiment.