[3 + 2] Coupling of Quinone Monoacetals with Vinyl Ethers Effected by Tetrabutylammonium Triflate: Regiocontrolled Synthesis of 2-Oxygenated Dihydrobenzofurans

Abstract

The synthesis of 2-oxygenated dihydrobenzofurans involving the [3 + 2] coupling of quinone monoacetals with vinyl ethers has been realized by tetrabutylammonium triflate catalysis. The reaction involves a new activation method of the acetal moiety in quinone monoacetals under acid-free conditions affording the highly oxygenated dihydrobenzofurans. This new activation mode was achieved by using the triflate anion catalyst for stabilization of the highly reactive cationic intermediate.

Recent Advances Towards the Synthesis of Dihydrobenzofurans and Dihydroisobenzofurans

“…Yasuyuki Kita et al revealed in 2021 an efficient and novel strategy for constructing 2-oxygenated 2,3-DHB derivatives 116 via n Bu 4 NOTf catalyzed [2 + 3] coupling of vinyl ethers 115 and quinone monoacetals 114. [112] The 2-oxygenated 2,3-dihydrobenzofurans 116 are formed through a novel activation technique of the acetal moiety in quinone monoacetals 114 in acid-free circumstances. The triflate anion (TfO À ) catalyst stabilized the exceedingly volatile cationic intermediate, resulting in this unique activation mode.…”