Synthesis of Benzoindolizines through 1,5-Electrocyclization/Oxidation Cascades

Abstract

This study presents a convenient synthesis of pyrrolo[1,2-a]quinolines and pyrrolo[2,1-a]isoquinolines with simple quinolines or isoquinolines and Morita−Baylis−Hillman carbonates in the presence of copper acetate. A range of functionalized benzoindolizines could be assembled through an S N 2′/deprotonation/1,5-electrocyclization/oxidation cascade pathway in a one-step process.

Formylation and Bromination of Pyrrolo[2,1-a]isoquinoline Derivatives with Bromoisobutyrate and Dimethyl Sulfoxide

“…All reagents and solvents were obtained from commercial sources and used without further purification. Compound 1 and 4 were prepared according to our reported procedure …”

“…In addition, the combination of bromoisobutyrate and dimethyl sulfoxide can also act as the bromination reagent if pyrroloisoquinolines without a methoxy group are employed. Here, we present our development of formylation and bromination of pyrroloisoquinolines using bromoisobutyrate and dimethyl sulfoxide …”

Synthesis of Imidazo[2,3‐a]isoquinoline and Imidazo[3,2‐a]quinoline Derivatives with Ynones, Isoquinolines and Quinolines

“…Functionalized ynone 2 a was used for a reaction with isoquinoline 1 a (Table 1). [15] To our delight, the desired imidazo[2,3‐ a ]isoquinoline 3 a can be isolated in 36% yield by stirring the reaction mixture at rt for 23 h (entry 1). The stereochemistry of compound 3 a was confirmed by X‐ray single crystal analysis [16] .…”

The Kröhnke synthesis of benzo[a]indolizines revisited: towards small, red light emitters

“…The mechanism of the last key step relies on the formation of vinylpyridinium ylides which are prone toward 1,5-electrocyclization. 65,66 The initially formed dihydroindolizine eliminates NO 2 − and furnishes the final aromatic product. The trouble with Kröhnke's approach is that it is mostly limited to explosive 1-chloro-2,4,6-trinitrobenzene.…”