Abstract:

Diels-Alder reaction of furan as diene provides an important intermediate — 7-oxanorbonene (1) — which is the precursor in the synthesis of many natural products such as terpene (2) and prostaglandin (3) analogues (Figure 1). It is reported that uncatalyzed Diels-Alder reactions of furan take several weeks to give low yields due to diene’s low reactivity. The use of Lewis acid catalysts or high pressures are described as efficient methods to improve reaction yields. Niobium compounds have been used as catalyst in various organic reactions and provided excellent yields with good selectivity in some cases. In this study, we describe our investigations on the use of niobium pentachloride (NbCl5) as catalyst in Diels-Alder reactions between furan and some reactive dienophiles.