A [4+3] annulation of benzofuran-derived azadienes and α-bromohydroxamates for the synthesis of benzofuran-fused 1,4-diazepinones

Abstract

A Cs2CO3-mediated formal [4+3] cycloaddition involving benzofuran-derived azadienes (BDAs) and α‑bromohydroxamates to afford benzofuran-fused 1,4-diazepinones is established. This is the first example of using BDAs for the construction of seven-membered...

Synthesis of Furo[2,3-e][1,4]diazepin-3-one Derivatives through Tandem Cyclization/[4 + 3] Annulation Reactions

“…Based on the above observation and the related literatures, ,, a plausible mechanism for the present one-pot transformation is illustrated in Scheme . First, metathesis of PPh 3 AuCl with AgSbF 6 led to the formation of active Au­(I) species.…”

Aza‐oxyallyl Cations and Their Applications in (3+m) Cycloaddition Reactions

“…Similarly, Fang et al. also depicted benzofuran‐derived azadienes 78 that could be used as the 4‐unit partner in [3+4]‐cycloaddition reaction within situ formed aza‐oxyallyl cations from α‐unsubstituted‐α‐halohydroxamates 90 leading to the formation of seven‐membered ring 99 in good yields under optimal reaction condition i. e., Cs 2 CO 3 as the base in CH 3 CN solvent [47b] . The reaction showed good functional group tolerance (Scheme 28).…”

“…(2020) [47a] and Fang et al. (2020) [47b] two different research group at the same time proposed 4‐unit cycloaddition partner 1‐azabutadienes 96 or 98 for trapping of 1,3‐dipolar aza‐oxyallyl cations. Yuan et al.…”

Access to 5,6-Spirocycles Bearing Three Contiguous Stereocenters via Pd-Catalyzed Stereoselective [4 + 2] Cycloaddition of Azadienes

“…A recent example by Zhao and co-workers illustrated a basecatalyzed [4 + 3] cycloaddition of 1 with α-bromohydroxamates, albeit in a racemic manner as well. 11 In our continuous efforts to construct novel fused or spirocyclic compounds from cycloaddition of 1, we chose vinyl benzoxazinanones 2 as the reaction partner, given that this substrate can easily be synthesized using commercially available reagents and has been established as a useful reagent in constructing Nheterocycles. 212 In this work, we report Pd-catalyzed [2 + 4] cycloaddition of 1 and 2 for the construction of novel spirocyclic tetrahydroquinoline scaffolds containing three contiguous stereocenters as a single diastereomer in high enantioselectivity (Scheme 1b).…”

“…Examples of nitrogen-containing dipoles being used as reaction partners with 1 are very limited. A recent example by Zhao and co-workers illustrated a base-catalyzed [4 + 3] cycloaddition of 1 with α-bromohydroxamates, albeit in a racemic manner as well . In our continuous efforts to construct novel fused or spirocyclic compounds from cycloaddition of 1 , we chose vinyl benzoxazinanones 2 as the reaction partner, given that this substrate can easily be synthesized using commercially available reagents and has been established as a useful reagent in constructing N-heterocycles …”