Regioselective [3 + 2] Cycloaddition Between Ynamides and Pyridine‐N‐Aminides Catalyzed by PicAuCl₂ Anchored Onto SBA‐15

Abstract

A dichloro(2‐pyridinecarboxylato)gold complex anchored on SBA‐15 (SBA‐15‐PicAuCl2) was conveniently prepared through the addition reaction between triethoxy(3‐isocyanatopropyl)silane and dichloro(3‐hydroxy‐2‐pyridinecarboxylato)gold complex and subsequent condensation with SBA‐15. The new heterogenized PicAuCl2 complex was fully characterized by using various analytic methods. In the existence of 5 mol% of SBA‐15‐PicAuCl2, the regioselective [3 + 2] cycloaddition reaction between ynamides and pyridine‐N‐aminides proceeded in toluene at 100°C for 1–24 h to deliver a wide array of functionalized trisubstituted 1,3‐oxazoles in 57%–95% yields. Ynamides with alkyl, benzyl, and aryl substituents as well as different sulfonyl groups at the nitrogen atom and the oxazolidinone‐derived ynamides were well‐tolerated. A wide range of pyridine‐N‐aminides bearing aroyl, naphthoyl, furoyl, vinylcarbonyl, alkylcarbonyl, and methoxycarbonyl were also allowed in the reaction. Moreover, SBA‐15‐PicAuCl2 is easy to recover through a simple centrifugation and recyclable at least seven cycles with only a slight drop in catalytic activity.