Palladium-catalyzed ortho-olefination of 2-arylpyrrolidines: A tool for increasing structural complexity in nitrogen heterocycles
The dual role of the (2-pyridyl)sulfonyl unit as directing functionality and readily removable N-protecting group has enabled an efficient and practical transformation of 2-arylpyrrolidine derivatives into more complex tricyclic frameworks via palladium-catalyzed ortho-olefination with electron deficient alkenes and subsequent cyclization upon N-deprotection under mild conditions. The key cross coupling step in the presence of N-fluoro-2,4,6-trimethylpyridinium triflate ([F+]) as the terminal oxidant is both highly efficient and tolerant to a variety of steric and electronic changes at both coupling partners. By adequate choice of reductive conditions, the N-sulfonyl deprotection can be directed to the selective formation of benzo-fused pyrrolizidine or fused pyrrolidino-benzazapine frameworks.
Legarda, Pablo D.,García-Rubia, Alfonso,Arrayás, Ramón Gómez,Carretero, Juan C.
p. 3947 - 3954
(2018/06/11)
Direct α-C-H bond functionalization of unprotected cyclic amines
Cyclic amines are ubiquitous core structures of bioactive natural products and pharmaceutical drugs. Although the site-selective abstraction of C-H bonds is an attractive strategy for preparing valuable functionalized amines from their readily available parent heterocycles, this approach has largely been limited to substrates that require protection of the amine nitrogen atom. In addition, most methods rely on transition metals and are incompatible with the presence of amine N-H bonds. Here we introduce a protecting-group-free approach for the α-functionalization of cyclic secondary amines. An operationally simple one-pot procedure generates products via a process that involves intermolecular hydride transfer to generate an imine intermediate that is subsequently captured by a nucleophile, such as an alkyl or aryl lithium compound. Reactions are regioselective and stereospecific and enable the rapid preparation of bioactive amines, as exemplified by the facile synthesis of anabasine and (-)-solenopsin A.
Chen, Weijie,Ma, Longle,Paul, Anirudra,Seidel, Daniel
p. 165 - 169
(2018/02/06)
Synthesis of 2-substituted pyrrolidines from nitriles
A novel and synthetically facile production of 2-substituted pyrrolidines from commercially available nitriles is reported herein. This methodology is operationally simple, and only requires the use of an extraction and a single chromatographic purificati
Ramachandran, P. Veeraraghavan,Mitsuhashi, Wataru,Nicponski, Daniel R.
p. 5001 - 5003
(2013/08/28)
A convenient method for C-azanucleosides synthesis