Rh(iii)-catalyzed spiroannulation of 3-arylquinoxalin-2(1H)-ones with alkynes: practical access to spiroquinoxalinones

Abstract

The use of imines as a H acceptor for Rh(iii)-catalyzed spirocyclization of 3-arylquinoxalinones and alkynes via a C–H functionalization/[3 + 2] annulation sequence has been achieved.

Transition‐Metal‐Catalyzed Synthesis of Spiro Compounds through Activation and Cleavage of C−H Bonds

“…With low catalytic loading, similar imine directed spiroannulation was extended to 3‐arylquinoxalin‐2(1 H )‐one substrates ( 65 ) which on reaction with alkynes (symmetrical) produced spiroquinoxalinones ( 66 , Scheme 15). [30] Unsymmetrical alkynes suffered from poor regioselectivity. Thus this synthesis of spiroquinoxalinones was limited to only symmetrical internal alkynes and only one unsymmetrical alkyne was tested for this annulation reaction.…”

Rhodium(iii)-catalyzed oxidative cross-coupling of benzoxazinones with styrenes via C–H activation

“…8 b ,20 Given the utility and high efficiency of the Rh( iii )-catalyzed oxidative alkenylations, it is necessary to further explore the oxidative coupling between arenes and styrenes, which will broaden the scope of Rh( iii )-catalyzed regioselective C–H alkenylation and accessed structurally diverse vinylarene molecules with styrenes. Although the imine-containing benzoxazinones and their derivatives have been rarely used in Rh( iii )-catalyzed C–H activation and annulation (Scheme 1b, right), 21 their wide applications in the construction of related heterocycles via asymmetric hydrogenation reactions have attracted our attention. 22 With our persistent interest in transition-metal-catalyzed C–H functionalization reactions, 23 we unraveled a novel method to rapidly assemble vinylarenes through Rh( iii )-catalyzed imine directing C–H alkenylation with high chemo- and regio-selectivity (Scheme 1c).…”

Sustainable C–H activation approach for palladium-catalyzed, regioselective functionalization of 1-methyl-3-phenyl quinoxaline-2(1H)-ones in water

“…These drawbacks can be easily eliminated by transition metal-catalyzed direct installation of functional groups on quinoxaline-2(1 H )-one (Scheme 1). 27 This methodology not only provides an economical and convenient alternative with high atom economy and good functional group tolerance but also delivers excellent regioselectivity with a wider substrate scope. In our continuous endeavour towards the development of a sustainable approach for the C–H functionalization of various biologically active molecules, 28 we herein report a green and sustainable broader method for the regioselective C–H acylation of quinoxalin-2(1 H )-one derivatives using commercially available aroyl surrogates such as aldehydes, toluenes and benzyl alcohols in water as a solvent and in the presence of palladium acetate as a catalyst.…”