Intramolecular Schmidt reactions of azides with carbocations: synthesis of bridged-bicyclic and fused-bicyclic tertiary amines

An Expeditious Synthesis of the Dendrobatid Indolizidine Alkaloid 167B

“…However, the isolated yield was modest (37%), almost certainly because the product is very volatile, as several authors have pointed out; Holmes and co-workers, for example, chose to isolate the alkaloid as its hydrochloride salt [7] . More to the point, the NMR spectra recorded on our product were in perfect agreement with those reported in the literature for indolizidine 167B [9] [11] [12] [15] [17] , and the 13 C-NMR spectrum in particular was quite different from that reported for the alternative diastereoisomer [11] . In summary, we have achieved a short (eight-step) synthesis of (±)-rel-(5R,9R)-indolizidine 167B (1) in an overall yield of 7.2% based on pyrrolidine-2-thione (5).…”

“…The reported route has the advantage of operational simplicity, and uses readily available and comparatively cheap precursors and reagents as well as straightforward chemical transformations. It is not only diastereoselective, but also shorter than all but three [9] [11] [12] of the published routes to indolizidine 167B. While it is not enantioselective, it can easily be made so by using an enantiomerically pure 3-aminohexanoate as chiral starting compound.…”

“…The structure and relative stereochemistry shown in 1 (which also shows the conventional numbering of the indolizidine system) are now accepted as correct, although the absolute configuration of the natural product remains uncertain. The alkaloid is a popular synthetic target, and syntheses of the racemic compound [7] [8] [9] [10] , the (5R,9R)-(Ϫ) enantiomer 1 [11] [12] [13] [14] [15] [16] [17] and the (5S,9S)-(ϩ) enantiomer ent-1 [18] have been published. The diastereoisomer 2 has also been synthesised as the racemate [8] and as clude a ring closure that takes advantage of the nucleophilicity of a vinylogous urethane 8, and stereoselective reduction of the C=C double bond of a bicyclic vinylogous amide 12.…”

Crystal structure of (1S,2R,5R,6R)-2-methoxy-6-(16-nitrophenylethynyl)-1-azabicyclo[3.2.2]nonane, C17H20N2O3

“…Although azabicyclo [ [3][4][5]. Due to uncertain stereochemical and mechanistic details of the hetero-cinchona rearrangement these reactions were reinvestigated [6], The resulting quinine and quinidine derivatives contain a 1-azabicyclo[3.2.2]nonane moiety.…”

Dipolare Restkopplungen als effektives Instrument der Konstitutionsanalyse: die unerwartete Bildung tricyclischer Verbindungen

“…Höchstwahr-scheinlich resultiert dann Aziridin 4 aus einer intramolekularen 1,3-dipolaren Cycloaddition, gefolgt von der Abgabe eines Stickstoffmoleküls. [14] Die Hypothese, dass die Aziridinbildung über Dien-Intermediat 3 abläuft und nicht über direkte Cyclisierung [15] …”