Merging dearomatization with redox-neutral C(sp³)–H functionalization via hydride transfer/cyclization: recent advances and perspectives

Abstract

This review highlights the encouraging advances in hydride transfer-involved dearomatization reaction during the past decade, the content of which is categorized according to the hydride acceptors, namely vinylogous imines and quinone methides.

Synthesis of oxindole fused 1,3-oxazepanes via hydride transfer initiated ring expansion of pyrrolidine

“…Recently, hydride transfer (HT) reactions have regained the interest of organic synthesis scientists due to their atom and step economy, redox neutrality and other characteristics. 4 Intramolecular hydride transfer reactions usually require the presence of strong electron-deficient groups as hydride acceptors, such as malonic esters, 5 ketones, 6 imines, 7 alkenyl ketones, 8 etc . 9 Recently, Li et al developed other novel hydride acceptors.…”

Dearomatization of 3-Aminophenols for Synthesis of Spiro[chromane-3,1′-cyclohexane]-2′,4′-dien-6′-ones via Hydride Transfer Strategy-Enabled [5+1] Annulations

“…Aromatic compounds as bulk and fundamental chemical feedstocks play a prominent role in organic synthesis [ 1 , 2 , 3 ]. Dearomatization is the high-value-added transformation of aromatic compounds to generate structurally diverse three-dimensional polycyclic molecules [ 4 , 5 , 6 , 7 ]. Due to the high significance of dearomatization in assembling sophisticated polycyclic architectures with enhanced sp 3 -character, much more attention has been paid to dearomatization chemistry [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ].…”

“…Dearomatization is the high-value-added transformation of aromatic compounds to generate structurally diverse three-dimensional polycyclic molecules [ 4 , 5 , 6 , 7 ]. Due to the high significance of dearomatization in assembling sophisticated polycyclic architectures with enhanced sp 3 -character, much more attention has been paid to dearomatization chemistry [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ]. Among the dearomatization reactions, phenol is one of the most studied structures which could be facilely converted into cyclohexadienone, and many strategies have been developed to achieve dearomatization of phenols [ 13 , 14 , 15 , 16 ].…”

“…As a continuation of our interest in developing hydride transfer-involved reactions for the rapid construction of privileged heterocyclic skeletons [ 7 , 22 , 34 , 35 , 42 ], herein we report the “two-birds-with-one-stone” strategy to dearomatize phenols and functionalize α-C(sp 3 )−H bond of oxygen. This dearomative [5+1] annulation provided a variety of cy spiro[chromane-3,1′-cyclohexane]-2′,4′-dien-6′-ones from 3-aminophenols and O -alkyl ortho -oxybenzaldehydes through Sc(OTf) 3 -catalyzed cascade condensation/[1,5]-hydride transfer/dearomative-cyclization process ( Scheme 1 f).…”

Formal oxygen atom insertion as a skeletal-editing step: rapid access natural-product-inspired bispiro[oxindole-oxazinane] hybrids

“…The structural complexity and richness in stereogenic centres of spirocyclic oxindoles greatly influence their biological activities. 8 Thus, the development of an efficient and straightforward methodology and enhancement in the structural diversity of spirocyclic oxindole compounds remain highly desirable for further biological evaluation but challenging. In 2017, Zhou and co-workers 9 reported a highly diastereo- and enantioselective [3 + 3] cycloaddition of spirocyclopropyl oxindoles and nitrones to afford structurally intriguing spiro[oxindole-oxazinane] hybrids (Scheme 1b).…”