Synthesis of Polycyclic Tertiary Carbinamines by Samarium Diiodide Mediated Cyclizations of Indolyl Sulfinyl Imines

Rao, Chintada Nageswara; Lentz, Dieter; Reißig, Hans‐Ulrich

doi:10.1002/anie.201408324

Cited by 29 publications

(24 citation statements)

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“…The synthesis of spirasine IV and XI (Scheme ) also involved a thiocarbonate group, rarely seen in SmI 2 ‐mediated reactions (see Section 5). In the synthetic route to these hetisine‐type heptacyclic C20‐diterpenoid alkaloids, one of the key steps is a SmI 2 ‐mediated radical coupling ( 124 → 125 ) to the arene moiety without prior dearomatization …”

Section: From Calchogen Derivativesmentioning

confidence: 99%

Radical Reactions in Alkaloid Synthesis: A Perspective from Carbon Radical Precursors

Bonjoch

Diaba

2020

Eur J Org Chem

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The usefulness of radical reactions in alkaloid synthesis is reviewed from the perspective of the functional groups embedded in the molecular structure of synthetic intermediates, that act as precursors of carbon‐centered radicals in the construction of new C–C bonds. The functional groups featured are alkenes, alkynes, halides (alkyl, vinyl, aryl), xanthates, sulfides, selenides, aldehydes, ketones, carboxylic acid derivatives (selenoesters, haloacetamides), β‐dicarbonyl compounds, and α‐heterosubstituted nitrogen‐compounds. The use of nitrogen‐centered radicals for C–N bond formation is also covered. Among the variety of radical processes applied, the most predominant are the hydride reductive method (Sn, Si), atom transfer radical reactions (Cu, Ru, B), and single‐electron transfer radical reactions promoted by Sm, Ni, Fe, Mn, Ti, and Ag. This review showcases the role radical reactions have played in the recent development of new strategies in alkaloid synthesis, as well as the implementation of new radical procedures in demanding substrates.

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Section: From Calchogen Derivativesmentioning

confidence: 99%

Radical Reactions in Alkaloid Synthesis: A Perspective from Carbon Radical Precursors

Bonjoch

Diaba

2020

Eur J Org Chem

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“…More recently, the Reissig group extended their SmI 2 -mediated dearomatizing cross-coupling methodology to the intramolecular addition of sulfinyl imines to indoles ( Scheme 22 ) [ 82 ]. Under the optimized conditions (SmI 2 –H 2 O–LiBr), sulfinyl imines undergo addition to the indole ring in good yields and modest to high diastereoselectivity.…”

Section: Synthesis Of Nitrogen Heterocycles Via Tethered Approachmentioning

confidence: 99%

Synthesis of Nitrogen Heterocycles Using Samarium(II) Iodide

Shi

Szostak

2017

Molecules

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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.

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“…Despite this unexpected setback we decided to investigate an enantioselective synthesis of dihydroindole derivatives using N ‐sulfinyl imine derivatives of type 26 (Scheme ) . These should lead to indolinyl‐substituted tertiary carbinamines that could be of relevance for the synthesis of natural products or their analogues.…”

Section: Our Second and Third‐generation Approachmentioning

confidence: 99%

Strychnine as Target, Samarium Diiodide as Tool: A Personal Story

Beemelmanns

Reißig

2015

The Chemical Record

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Strychnine stands out from the group of classical natural products as one of the first complex compounds to be isolated in pure form and an extreme challenge to be structurally characterized. It has played a central role in natural product total syntheses and the surge in the development of innovative synthetic methods for many decades. Recently, we have accomplished one of the shortest formal total syntheses of strychnine (in ten steps and 14% overall yield or even shorter in eight steps and 10% overall yield). The evolution of a productive synthetic strategy, as well as the synthetic challenges tackled, are described here in detail, including examples of related transformations. The successful synthetic strategy was inspired by the premise that the core structure could be derived from simple aromatic indole precursors by a reductive SmI2 -induced ketyl-aryl coupling. Other key reactions included a diastereoselective reduction and a regioselective elimination protocol. Altogether one of the shortest syntheses of iso-strychnine and hence of strychnine was established.

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Synthesis of Polycyclic Tertiary Carbinamines by Samarium Diiodide Mediated Cyclizations of Indolyl Sulfinyl Imines

Cited by 29 publications

References 50 publications

Radical Reactions in Alkaloid Synthesis: A Perspective from Carbon Radical Precursors

Radical Reactions in Alkaloid Synthesis: A Perspective from Carbon Radical Precursors

Synthesis of Nitrogen Heterocycles Using Samarium(II) Iodide

Strychnine as Target, Samarium Diiodide as Tool: A Personal Story

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