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Molecules 2017, 22(11), 2018;

Synthesis of Nitrogen Heterocycles Using Samarium(II) Iodide

Department of Chemistry, Rutgers University, 73 Warren Street, Newark, NJ 07102, USA
Author to whom correspondence should be addressed.
Received: 27 October 2017 / Revised: 11 November 2017 / Accepted: 13 November 2017 / Published: 21 November 2017
(This article belongs to the Section Organic Chemistry)


Nitrogen heterocycles represent vital structural motifs in biologically-active natural products and pharmaceuticals. As a result, the development of new, convenient and more efficient processes to N-heterocycles is of great interest to synthetic chemists. Samarium(II) iodide (SmI2, Kagan’s reagent) has been widely used to forge challenging C–C bonds through reductive coupling reactions. Historically, the use of SmI2 in organic synthesis has been focused on the construction of carbocycles and oxygen-containing motifs. Recently, significant advances have taken place in the use of SmI2 for the synthesis of nitrogen heterocycles, enabled in large part by the unique combination of high reducing power of this reagent (E1/2 of up to −2.8 V) with excellent chemoselectivity of the reductive umpolung cyclizations mediated by SmI2. In particular, radical cross-coupling reactions exploiting SmI2-induced selective generation of aminoketyl radicals have emerged as concise and efficient methods for constructing 2-azabicycles, pyrrolidines and complex polycyclic barbiturates. Moreover, a broad range of novel processes involving SmI2-promoted formation of aminyl radicals have been leveraged for the synthesis of complex nitrogen-containing molecular architectures by direct and tethered pathways. Applications to the synthesis of natural products have highlighted the generality of processes and the intermediates accessible with SmI2. In this review, recent advances involving the synthesis of nitrogen heterocycles using SmI2 are summarized, with a major focus on reductive coupling reactions that enable one-step construction of nitrogen-containing motifs in a highly efficient manner, while taking advantage of the spectacular selectivity of the venerable Kagan’s reagent. View Full-Text
Keywords: samarium iodide; nitrogen heterocycles; nitrogen; radicals; reductive coupling; SmI2; radical cyclizations; samarium diiodide; umpolung cyclizations; aminoketyl radicals samarium iodide; nitrogen heterocycles; nitrogen; radicals; reductive coupling; SmI2; radical cyclizations; samarium diiodide; umpolung cyclizations; aminoketyl radicals

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Shi, S.; Szostak, M. Synthesis of Nitrogen Heterocycles Using Samarium(II) Iodide. Molecules 2017, 22, 2018.

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