A Synthesis of Arylboronates via the Palladium(0)-Catalyzed Cross-Coupling Reaction of

Abstract: Tetrakis(alkoxo)diborons cross-coupled with aryl triflates at 80 ｡C in the presence of PdCl2(dppf)-dppf catalyst and KOAc in dioxane, producing arylboronates in excellent yields. The synthetic utility of the method was demonstrated by the tandem coupling between two non-identical aryl triflates to give unsymmetrical biaryls. Recent studies on the transformations of tetrakis(alkoxo)diborons1 (1) by transition-metal catalysis provide new methodology for the synthesis of organoboron compounds. The addition of 1 to alkynes,2 1,3-dienes,3 and alkenes4 is effectively catalyzed by Pt(0), Rh(I), or Au(I) complex to provide a convenient access to stereodefined bis(boryl)alkenes, bis(allyl)boronates, and bis(boryl)alkanes. The mechanism was postulated to proceed through the oxidative addition of 1 to the low-valent metal complex to form bis(boryl)metal intermediate. Alternative route from 1 to organoboron compounds is the Pd(0)-catalyzed cross-coupling with organic electrophiles, which involves the transmetalation of boryl group from 1 to R-Pd(II)-X intermediate. Haloarenes5 and allyl acetates6 smoothly coupled with 1 in the presence or absence of base to afford the corresponding aryl- and allylboronates. As a part of our program on the direct borylatio