Construction of Oxepino[3,2‐b]indoles via [4+3] Annulation of 2‐Ylideneoxindoles with Crotonate‐Derived Sulfur Ylides

Abstract

A [4+3] annulation of 2‐ylideneoxindoles with crotonate‐derived sulfur ylides has been developed. A series of oxepino[3,2‐b]indoles were prepared in moderate to excellent yields (62‐93%) under mild conditions. Moreover, the synthetic oxepino[3,2‐b] indoles can be further transformed into more complex cyclopropa[5,6]oxepino[3,2‐b]indoles via a [2+1] cyclopropanation. In addition, the synthetic compounds show certain antiproliferative activity against K562 and MCF‐7 cells, and its IC50 values for these two kinds of tumor cells up to 5.40±0.88 μM and 18.41±0.50 μM, respectively.

Synthesis of diarylmethyl thioethersviaa DABCO-catalyzed 1,6-conjugate addition reaction ofp-quinone methides with organosulfur reagents

“…1,4-Dithiane-2,5-diol, as a mercaptoacetaldehyde dimer, is more convenient and efficient than common organic thiols and used widely in organic synthesis, 19 especially in the diverse synthesis of thiophenes structures. 20 With our continuing interest in organic sulfur chemistry, 21,22 we herein describe a DABCO-catalyzed 1,6conjugate addition reaction of p-QMs with 1,4-dithiane-2,5-diol to realize the synthesis of diarylmethyl thioethers (Scheme 1e).…”

Substrate-directed divergent annulations of sulfur ylides: synthesis of functionalized bispirocyclopentane and bispirocyclopropane derivatives

“…13 For the [2 + 3] annulations, oxindole-derived pyrazolones 1 tended to react with γ-selective allylic ylides II through an intermolecular Michael addition, affording a zwitterionic intermediate III . Next, intermediate III transformed into intermediate IV via two proton shift processes, 14 followed by an intramolecular nucleophilic substitution to produce the [2 + 3] annulation products 3 . On the other hand, owing to the different inherent steric hindrance between the oxindole moiety and pyrazolone, isoindigos 4 tended to work with α-selective allylic ylides I and led to intermediate V .…”