Asymmetric functionalization of benzenes via an organocatalytic hetero-Diels–Alder reaction. Issue 71 (17th August 2022) - Ali, Shaukat
Abstract : From flatland to value-added 3D! A quinine-derived amide can efficiently catalyze the asymmetric conversion of nonactivated planar benzene derivatives to enantioenriched three-dimensional products via the application of a hetero-Diels–Alder reaction under mild conditions. Abstract : Benzene derivatives are readily available and stable sources of substrates that can be transformed into complex three-dimensional structures via asymmetric synthesis. The increasing complexity and chirality of products are crucial for functional materials and drug discovery. While planar aromatics can be converted into enantioenriched products by catalytic asymmetric dearomatization reactions, most of the methods are limited to heteroarenes and activated arenes. Available transition metal-catalyzed and/or photoredox methods using nonactivated arenes are rare. This paper highlights the most recent studies directed toward the development of the first organocatalytic asymmetric dearomatizing strategy to access complex stereochemical products from nonactivated arenes via harnessing the unique reactivity of in situ generated chiral vinylidene ortho -quinone methides (VQMs). With this methodology, nonactivated benzenes were regioselectively converted into chiral spirocyclic products and chiral oxahelicenes with excellent stereoselectivities. Mechanistic studies revealed the formation of a chiral VQM that disrupts the aromaticity of benzenes via a hetero-Diels–Alder reaction.