Visible‐Light‐Induced Oxidation of Diazenyl‐Protected Tetrahydroisoquinolines and Isoindolines for the Synthesis of Functionalized Lactams

Abstract

A visible-light-induced oxidation of diazenyl-protected tetrahydroisoquinolines and isoindolines for the synthesis of structurally diverse lactams is developed. The reaction was carried out with Eosin Y-Na 2 as an organic photocatalyst and molecular oxygen as an oxidant, and the desired functionalized N-aryldiazenyl-lactams were obtained under mild and transition metal-free conditions. The utility of this method is showcased by the gram-scale synthesis and deprotection of the Naryldiazenyl-lactam product.

A photo-driven traceless group directed electron–donor–acceptor (EDA) complex initiated radical coupling/dehydrogenation tandem reaction: access to 1-allyl/benzyl-3,4-dihydroisoquinoline

“…Therefore, employing traceless directing groups would be a beneficial alternative to the traditional strategies. 37,38 In this context, inspired by these findings and our previous work, 39–42 we hypothesized that triazenes could be used as traceless directing groups for the one pot EDA complex initiated radical coupling/dehydrogenation of arylazo-protected tetrahydroisoquinolines with benzyl/allyl bromide under mild and transition-metal-, photocatalyst- and oxidant-free conditions. Our experimental results disclose that installation of triazene groups can largely improve the α-allylation of tetrahydroisoquinolines via EDA complex promotion (Scheme 1c).…”

Evaluation of Phenyldiazenyl as a Protective/Activating Group in Lithiation–Substitution Reactions of Tetrahydroisoquinolines

“…52,74 Since lithiation-electrophilic substitution reaction of Nphenyldiazene-protected THIQs gave good results even with bulky electrophiles, i.e., ethyl benzoate and benzophenone, a similar reaction was attempted for the C-1 arylation of N-phenyldiazene-protected THIQs via intermolecular coupling of -amino carbanions and in situ generated arynes (Scheme 6). 66 For this, the reaction of -aminocarbanion 3.Li prepared from 3a (1 equiv) with in situ generated arynes generated from chlorobenzene (6a, 3 equiv) and s-BuLi (3 equiv) furnished 1-aryl-N-phenyldiazene THIQ 7a in 65% yield. 75 Similarly, the reaction proceeded well with other substrates to furnish 7b-e in moderate yields.…”

“…65 Recently, visible-light-induced oxidation of diazenyl-protected THIQs has been reported by Zhang et al for the synthesis of various lactams. 66 Following our work with bis(dimethylamino)phosphinoyl 67 and 4,5-dihydrothiazoline 68 we became interested in C-1 functionalization of THIQs using phenyldiazene as the protecting group has not been explored yet. In this paper, we describe the synthesis of various C-1-substituted THIQs via lithiation–substitution of N -phenyldiazene-1,2,3,4-THIQs using different electrophiles/arynes (Scheme 1 ).…”

Pd-Catalyzed C-7 Arylation of Indolines with Aryltriazenes under Mild Conditions

“…Recently, Wang and our group reported the palladium-catalyzed C-2 arylation of indoles with aryltriazenes in acidic medium (Scheme c). , However, to the best of our knowledge, the direct C-7 arylation of indolines with aryltriazenes has not been achieved to date. Due to our continuous interest in the aryltriazene-based direct C–H functionalization of heterocyclic compounds, ,,, we envisioned that the C-7 arylated indolines could be obtained through palladium-catalyzed regioselective C-7 arylation of indolines with aryltriazenes via C–H bond activation under mild conditions, which will provide a simple way for the synthesis of C-7 arylated indoline or indole derivatives (Scheme d).…”