Indolizidine and quinolizidine alkaloids

Synthesis of Indolizines and Benzoindolizines by Annulation of Donor‐Acceptor Cyclopropanes with Electron‐Deficient Pyridines and Quinolines

“…This report describes our results from an exploration of this new synthetic pathway for preparing indolizines, the skeleton of which appears in biologically active natural products, [5] medicinal chemistry, [6] dyes [7] and agrochemicals. [8] Many creative methods have been devised for their synthesis.…”

Rhodium(III)‐Catalyzed Intramolecular Annulation through CH Activation: Total Synthesis of (±)‐Antofine, (±)‐Septicine, (±)‐Tylophorine, and Rosettacin

“…In 2010, Li and co-workers reported the rhodium(III)-catalyzed synthesis of 2-pyridones through oxidative alkene C(sp 2 )ÀH activation of N-arylacrylamides. [14] While this represents a remarkable progress, the regioselectivity of the coupling with unsymmetrical alkynes is moderate.…”

“…While a number of synthetic methods for the construction of these scaffolds have been reported, [1][2][3][4] the development of conceptually different synthetic approaches is still of great interest.The rhodium(III)-catalyzed oxidative CÀH activation has received significant interest in recent years because of its high efficiency, selectivity, and functional-group tolerance.[5] Generally, these reactions require stoichiometric amounts of external oxidants [Eq. (1)], [6] thus resulting in the generation of undesired waste.…”

“…Our synthetic attempts began with the reaction of 7 a by employing Fagnous intermolecular reaction conditions [7] ( 2 ], 3.0 mol %) [11] also gave the isoquinolones in excellent yields, however, with poor regioselectivity (3:1; Table 1, entry 5). The structure of 8 a was unambiguously assigned by 1 H/ 13 C NMR spectroscopy and X-ray crystallography.…”

“…

The indolizidine structural motif forms the core of many natural products with pharmacological relevance, such as indolizidine [1] and phenanthroindolizidine [2] alkaloids (septicine (1), antofine (2), and tylophorine (3)), camptothecin (4, CPT), [3] and aromathecin alkaloids [4] (rosettacin (5) and 22-hydroxyacuminatine (6)). While a number of synthetic methods for the construction of these scaffolds have been reported, [1][2][3][4] the development of conceptually different synthetic approaches is still of great interest.

The rhodium(III)-catalyzed oxidative CÀH activation has received significant interest in recent years because of its high efficiency, selectivity, and functional-group tolerance.

[5] Generally, these reactions require stoichiometric amounts of external oxidants [Eq.

…”