Metal‐Free Cyclization ofortho‐Nitroaryl Ynamides and Ynamines towards Spiropseudoindoxyls

Abstract

An efficient metal-free cascade reaction between 1-dibromovinyl-2-nitro-substituted arenes and secondary amines results in the formation of polycyclic pseudoindoxyls in a single step. The reaction mechanism leading to these fused ring systems was investigated, and is believed to involve the initial formation of nitroarylated ynamines/ynamides. These intermediates cycloisomerize towards N-alkenyl-tethered 2-aminoisatogens via a carbene intermediate as demonstrated by QTAIM (quantum theory of atoms in molecules) and ELF (electron localization function) analysis. A subsequent intramolecular dipolar cycloaddition afforded the title compounds.

Recent Advances in the Synthesis of Heterocycles via Reactions Involving Elemental Sulfur

“…ortho-Nitrophenylethylnyl thiother 184 generated in situ from trimethylsilyl alkyne 182 was found to undergo a cascade of reactions to tetracycle 185 at rt (Scheme 59). [67] Since the isolation proved to be complex, this reaction was not further developed.…”

Cs2CO3-Mediated Regio- and Stereoselective Sulfonylation of 1,1-Dibromo-1-alkenes with Sodium Sulfinates

“…Subsequently, the -addition of ArSO 2 − to intermediate A formed B. 16,23 Intermediate B was subjected to intramolecular oxa-Michael addition to yield C. 24 The ring opening of C followed by base promoted the intramolecular hydroalkylation of nitroso group to afford E. 25 Final-…”

An Efficient Approach to 2-CF3-Indoles Based on ortho-Nitrobenzaldehydes

“…Even in the case of enamine 3a we observed formation of 5a in 4% yield (by 19 F NMR). We did not investigate this side reaction thoroughly, but possible mechanism of this transformation was proposed using the literature data ( Scheme 3 ) [ 94 , 95 ]. At first step dehydrochlorination of 2c leads to alkyne 6 [ 78 ].…”