Copper-Catalyzed Diacetoxylation of Olefins using PhI(OAc)2 as Oxidant
摘要:
Copper(I) or -(II) salts with weakly coordinating anions catalyze the diacetoxylation of olefins efficiently in the presence of PhI(OAc)(2) as the oxidant under mild conditions, The reaction is effective for aryl, aryl alkyl, as well as aliphatic terminal and internal olefins forming the corresponding vicinal diacetoxy compounds in 70-85% yields and dr (syn/anti) of up to 5.2. Under these conditions, homoallylic alcohols formed the corresponding tetrahydrofuran derivatives in high yields.
For the first time, an asymmetric electrosynthetic reaction mediated by a catalytic amount of chiral iodoarene has been accomplished. Important aspects of the design of such transformations are disclosed, providing guidance for the development of novel enantioselective iodoarene-catalyzed processes promoted electrochemically.
A novel palladium-catalyzed alkene diacetoxylation with dioxygen (O-2) as both the sole oxidant and oxygen source is developed, which was identified by O-18-isotope labeling studies. Control experiments suggested that bis(pinacolato)diboron (B(2)pin(2)) played a dominant intermediary role in the formation of a C-O bond. This method performed good functional group tolerance with moderate to excellent yields, which could be successfully applied to the late-stage modification of natural products. Furthermore, an atmospheric pressure of dioxygen enhances the practicability of the protocol.