Copper-Catalyzed Borylative Cyclization of Substituted N-(2-Vinylaryl)benzaldimines

Abstract

A t-BuOCu-initiated reaction sequence of styrene borometalation and intramolecular imine addition has been achieved using a Cu(OTf)/dppf combination as catalyst. The product of this reaction cascade is a useful 2,3-disubstituted indoline bearing a versatile boryl moiety and is formed with sole cis-selectivity. To account for the observation of the exclusive formation of cis-stereoisomers, a transition state featuring copper-imine coordination is suggested. The application to the synthesis of antioxidant tetrahydroindenoindoles is described.

Enantioselective Intramolecular Copper‐Catalyzed Borylacylation

“…Although intramolecular termination has been explored, [7] there have been few examples in the synthesis of heterocycles. [8] In 2017, Brown and co-workers reported preliminary results on enantioselective borylacylation (Scheme 1). [9] Recent efforts to further this methodology have focused on utilizing different acylatingreagents.…”

Cation-induced ring-opening and oxidation reaction of photoreluctant spirooxazine–quinolizinium conjugates

“…In 3a and 3b, the electron density of the phenolate oxygen atom was significantly reduced due to the direct conjugation with the strong electron-accepting styrylquinolinizium unit at the neighboring carbon atom C5''. At the same time, imine groups also have a high binding affinity to Cu 2+ [83][84][85] and Fe 3+ [86,87] so that we propose the initial coordination of the metal cation mainly to the imine nitrogen atom of the spirooxazine group in the course of the reaction (Scheme 4, A). Moreover, this explanation is in agreement with the occurrence of the additional set of signals at small copper-to-ligand ratios (Figure 5B,C and Figure S6B,C, Supporting Information File 1, marked with green asterisks) and with the course of the spectrophotometric titration (Figure 2), thus indicating that the initial coordination of the copper ion to the closed form of the spirooxazine was the rate-determining step of the reaction.…”

Copper‐Catalyzed Borylative Couplings with C−N Electrophiles

“…A range of (hetero)aryl substituents on the imines and aryl‐substitutents on the alkene was well tolerated (Scheme 6 B). Shen, Xu and co‐workers [30a] reported a diastereoselective variant using dppf L5 (Scheme 6 C). Interestingly, the products arising from the reaction of 2‐bromo‐aryl imines were further transformed into the corresponding tetrahydroindenoindoles 25 through a palladium‐catalyzed Suzuki–Miyaura coupling.…”