- Polycyclic Pyrazolidines by Tandem Diazomalonate Dipolar Cycloadditions and CpRu-Catalyzed Carbene Additions
Montagnon, C.; Bultel, J. R.; Besnard, C.; Guénée, L.; Lacour, J.
Chem. Eur. J. 2024, e202401522
Thanks to the ability of diazo derivatives to react either as 1,3-dipoles and as carbenes after dinitrogen extrusion, combinations of oxa or aza benzonorbornadienes and diazomalonates afford polycyclic pyrazolidines via a three-step sequence of (i) a highly diastereoselective [3+2]-cycloaddition, (ii) a CpRu-catalyzed carbene addition, and (iii) a second dipolar cycloaddition. Of importance, step (II) represents a unique access to novel bench-stable N,N-cyclic azomethine imines, which behave as effective 1,3-dipoles in combination with electron-poor dipolarophiles. Each step proceeds efficiently and the 3-step process can be performed in one-pot to yield a polycyclic pyrazolidine in excellent overall yield (90%).
DOI : 10.1002/chem.202401522
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