(Bio)isosteres of ortho- and meta-substituted benzenes

• H. Erik Diepers and
• Johannes C. L. Walker

Beilstein J. Org. Chem. 2024, 20, 859–890, doi:10.3762/bjoc.20.78

• polysubstituted BCHs, as shown by Walker and co-workers in their synthesis of tri- and polysubstituted BCHs. These include 1,2,4-BCH 191, which they described as a saturated analogue of fendizoic acid [34]. The previously discussed samarium-catalysed synthesis of BCHs (Scheme 3) reported by Procter and co-workers

One-pot nucleophilic substitution–double click reactions of biazides leading to functionalized bis(1,2,3-triazole) derivatives

• Hans-Ulrich Reissig and
• Fei Yu

Beilstein J. Org. Chem. 2023, 19, 1399–1407, doi:10.3762/bjoc.19.101

• reaction time and the fairly high amount of catalyst employed. As an alternative method, which should be more chemoselective, we examined the reduction with samarium diiodide [60]. This versatile one-electron transfer reagent is known to cleave N–O bonds with high selectivity [61][62] and was applied

• several times by our group with good success for reductive ring-openings of 1,2-oxazine derivatives [63][64]. A slight excess of samarium diiodide in tetrahydrofuran completely consumed compound 21 within five hours. Compound 26 was isolated in 50% yield, but again the sample was not clean. The NMR data

• reductive ring openings of bis(1,2,3-triazole) derivative 21 to divalent carbohydrate mimetics with hydrogen under palladium catalysis or with samarium diiodide did not proceed cleanly and need further optimization. Earlier approaches to multivalent carbohydrate mimetics B, D or F based on enantiopure

Strategies to access the [5-8] bicyclic core encountered in the sesquiterpene, diterpene and sesterterpene series

• Cécile Alleman,
• Charlène Gadais,
• Laurent Legentil and
• François-Hugues Porée

Beilstein J. Org. Chem. 2023, 19, 245–281, doi:10.3762/bjoc.19.23

• by a vinyl ketone (compound 135) or a butenolide (compound 137) moiety dramatically influenced the outcome of the reaction and no cycloadduct was observed in both cases (Scheme 27). 4 Radical cyclization (including SmI2) Introduced by Kagan more than four decades ago, samarium diiodide (SmI2) has

1,4-Dithianes: attractive C2-building blocks for the synthesis of complex molecular architectures

• Bram Ryckaert,
• Ellen Demeyere,
• Frederick Degroote,
• Hilde Janssens and
• Johan M. Winne

Beilstein J. Org. Chem. 2023, 19, 115–132, doi:10.3762/bjoc.19.12

• acetylenes in Diels–Alder reactions [49], since desulfonylation of the cyclohexene-disulfones with sodium amalgam or samarium(II) iodide affords 1,4-cyclohexadienes (Scheme 8). In a comparative study by Nakayama [50], the dithiin-type cyclic disulfone 7 emerged as a much stronger dienophile than any other

Combining the best of both worlds: radical-based divergent total synthesis

• Kyriaki Gennaiou,
• Antonios Kelesidis,
• Maria Kourgiantaki and
• Alexandros L. Zografos

Beilstein J. Org. Chem. 2023, 19, 1–26, doi:10.3762/bjoc.19.1

• [16]. Based on their reactivity, major contributions in carbon-centered radical formation followed, consequently unlocking highly predictable intramolecular reactions, deoxygenation protocols (Barton–McCombie reaction) [17], etc. Other reagents that majorly contributed were samarium diiodide for the

• reduction of the amide using Wilkinson’s catalyst provided diastereoisomeric indole 131. Careful manipulation of the nitrile and alcohol side chains allowed selective cyclizations to the nitrogen atom of the indole core to conclude the total syntheses of 132–134. Samarium diiodide-mediated reductive

• , bipolamine I (176) was obtained from 169 via a samarium diiodide reduction of the mesylate, followed by sodium borohydride reduction of the ketone, hydroboration, and base-mediated cyclization. Flow-controlled divergent synthesis of aporphine and morphinandienone natural products (Felpin 2022) [92

N-tert-Butanesulfinyl imines in the asymmetric synthesis of nitrogen-containing heterocycles

• Joseane A. Mendes,
• Paulo R. R. Costa,
• Miguel Yus,
• Francisco Foubelo and
• Camilla D. Buarque

Beilstein J. Org. Chem. 2021, 17, 1096–1140, doi:10.3762/bjoc.17.86

Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

• to fuse samarium oxide nanoparticles to TiO2 and ceria (CeO2) as a bifunctional heterogeneous photoredox Lewis acid catalyst for reductive cyclisation reactions, previously reported with ruthenium transition metal complex photocatalysts [157]. Both electrochemical and photochemical deposition

Heck- and Suzuki-coupling approaches to novel hydroquinone inhibitors of calcium ATPase

• Robert J. Kempton,
• Taylor A. Kidd-Kautz,
• Soizic Laurenceau and
• Stefan Paula

Beilstein J. Org. Chem. 2019, 15, 971–975, doi:10.3762/bjoc.15.94

• appended. Unfortunately, reactions of 6 and 8 utilizing catalytic hydrogenation, lithium aluminium hydride by itself as well as with added aluminium chloride or samarium iodide produced only trace amounts of an amine (e.g., 9). When samarium iodide was used as the reagent, the only discernible product (not

Synthesis of eunicellane-type bicycles embedding a 1,3-cyclohexadiene moiety

• Alex Frichert,
• Peter G. Jones and
• Thomas Lindel

Beilstein J. Org. Chem. 2018, 14, 2461–2467, doi:10.3762/bjoc.14.222

• have also been obtained (TiCl4/Zn [12][13][14][15][16][17] or TiCl3/Zn-Cu [18][19][20]), often as mixture of diastereomers. The use of samarium diiodide to achieve the pinacol coupling was not advised, since we had observed that intially formed ketyl radicals would add to the alkyne moiety [11], even

• on reaction with TiCl4/Zn/pyridine (27, Scheme 3) without cyclization. As before, the aldehyde had stayed in place. Interestingly, treatment of 25 with samarium diiodide afforded the primary alcohol and left the keto group unchanged. Still, no cyclization took place. One could think that endocyclic

Recent developments in the asymmetric Reformatsky-type reaction

• Hélène Pellissier

Beilstein J. Org. Chem. 2018, 14, 325–344, doi:10.3762/bjoc.14.21

• actually 30-epiapratoxin E, thus correcting the originally proposed absolute configuration. Both diastereomers were tested for their antiproliferative activities in HCT116 cells, showing that natural (30R)-apratoxin E exhibited a higher activity than its (30S)-epimer. Due to their lower basicity, samarium

• enolates can be considered as valuable alternatives to lithium enolates. Consequently, a number of samarium-mediated Reformatsky reactions have been developed. For example, SmI2 was found by Rinner et al. to mediate the diastereoselective Reformatsky reaction between chiral aldehyde 11 derived from D

• THF at −78 °C to give the corresponding chiral secondary alcohol 19 in high yield (88%) combined with excellent diastereoselectivity (>95% de). Six supplementary steps allowed prostaglandin E2 methyl ester to be achieved in 24% overall yield. In addition to zinc and samarium, SnCl2 is also capable to

Recent progress in the racemic and enantioselective synthesis of monofluoroalkene-based dipeptide isosteres

• Myriam Drouin and
• Jean-François Paquin

Beilstein J. Org. Chem. 2017, 13, 2637–2658, doi:10.3762/bjoc.13.262

• after HWE olefination using dimethyl phosphonoacylsilane 54, was found to facilitate the NHC-catalyzed reduction and gave in this way the dipeptide isostere 56 in excellent yield. The defluorinative reduction could also be performed using samarium iodide. Altman and co-workers proposed the synthesis of

Adsorption of RNA on mineral surfaces and mineral precipitates

• Elisa Biondi,
• Yoshihiro Furukawa,
• Jun Kawai and
• Steven A. Benner

Beilstein J. Org. Chem. 2017, 13, 393–404, doi:10.3762/bjoc.13.42

• the RNA. The green color is often attributed to small amounts of iron or samarium within the mineral lattice. This difference, although observed on only two different specimens from two different sources, is cautionary. Materials and Methods Radiolabeled RNA For this study, a 83-nt long labeled RNA

The reductive decyanation reaction: an overview and recent developments

• Jean-Marc R. Mattalia

Beilstein J. Org. Chem. 2017, 13, 267–284, doi:10.3762/bjoc.13.30

• NHC-boryl nitrile 74, EPR spectroscopy observations [122], and polar effects fit with this proposition. Neutral organic electron donors Powerful single-electron transfer reagents have been described. Kang et al. reported the decyanation of both malononitriles and α-cyanoesters using samarium(II

• ) iodide/THF/HMPA at respectively 0 °C and room temperature [123]. Metallic samarium can also promote the decyanation [124]. Doni and Murphy have reported the reductive decyanation of malononitriles and α-cyanoesters by using the neutral organic electron donor 78 (Scheme 25) under photoactivation (method A

Stereoselective synthesis of tricyclic compounds by intramolecular palladium-catalyzed addition of aryl iodides to carbonyl groups

• Jakub Saadi,
• Christoph Bentz,
• Kai Redies,
• Dieter Lentz,
• Reinhold Zimmer and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2016, 12, 1236–1242, doi:10.3762/bjoc.12.118

• reaction requires a reduction of palladium(II) back to palladium(0) which is apparently achieved by the present triethylamine. Keywords: 1,2-addition; aryl iodides; ketones; nucleophilic addition; palladium catalysis; Introduction For our systematic studies on samarium diiodide promoted cyclizations

Conjugate addition–enantioselective protonation reactions

• James P. Phelan and
• Jonathan A. Ellman

Beilstein J. Org. Chem. 2016, 12, 1203–1228, doi:10.3762/bjoc.12.116

• lower enantioselectivities for the addition of para-substituted anilines to α,β-unsaturated imines [41]. Gil and Collin have also reported on the same reaction as Sodeoka, but using a samarium-BINOL catalyst system, which proceeded with lower enantioselectivity [42]. Sodeoka found that minimizing the

• co-workers demonstrated that chiral lanthanum and samarium tris(BINOL) complexes (Figure 3), developed by the Shibasaki group for asymmetric Michael additions using malonates and organometallic reagents, are effective catalysts for the sequential conjugate addition of 4-tert-butyl(thiophenol) to α,β

• could be achieved, the saturated ester product 146 could not be obtained in greater than 50% yield. In contrast, the unsaturated thioester 145 (X = S) provided the product in high yield and enantioselectivity. By switching to samarium catalyst (R)-Sm-143, the catalyst loading could be halved and a

Synthesis of Xenia diterpenoids and related metabolites isolated from marine organisms

• Tatjana Huber,
• Lara Weisheit and
• Thomas Magauer

Beilstein J. Org. Chem. 2015, 11, 2521–2539, doi:10.3762/bjoc.11.273

• silylation and oxidation afforded aldehyde 123. Next, the formation of the cyclobutanol ring was realized by an intramolecular samarium diiodide-mediated radical conjugate addition to afford tricycle 124 in 60% yield. Introduction of the dihydropyran ring of plumisclerin A (118) was envisioned to be carried

SmI₂-mediated dimerization of indolylbutenones and synthesis of the myxobacterial natural product indiacen B

• Nils Marsch,
• Peter G. Jones and
• Thomas Lindel

Beilstein J. Org. Chem. 2015, 11, 1700–1706, doi:10.3762/bjoc.11.184

• treatment of the indolylbutenone 5 with samarium diiodide in THF (formed from Sm and diiodoethane), the dimeric bisindolylcyclopentanes 6 (26%), 7 (27%) and a mixture of 8 and the open-chain dimer 9 (16%, 4:1) were isolated by semipreparative HPLC. The structures were elucidated by 2D NMR spectroscopy and

• observed an intermolecular reaction with ketones only if the 3-position was substituted with an electron-withdrawing group [29]. There are also several examples of SmI2-induced cyclization of indolylketones [30]. Further applications of samarium reagents in organic synthesis can be found in reviews by

Diastereoselective and enantioselective conjugate addition reactions utilizing α,β-unsaturated amides and lactams

• Katherine M. Byrd

Beilstein J. Org. Chem. 2015, 11, 530–562, doi:10.3762/bjoc.11.60

• ). Molander and Harris developed the samarium(II) iodide-mediated cyclization of α,β-unsaturated esters and amides [167] (Scheme 20). Previous methods for the cyclization of alkyl halides and α,β-unsaturated carbonyl systems include: (1) tin-mediated radical cyclization [168] or (2) nucleophilc cyclization

• enantioselectivities when both electron-deficient and -rich anilines were added (Scheme 34). In 2008, Collin and co-workers developed the asymmetric aza-Michael addition of N-alkenoyloxazolidinones catalyzed by iodo(binaphtholato)samarium [243]. This group had previously reported the use of samarium diiodide in the

• )samarium-catalyzed asymmetric aza-Michael addition provided the 1,4-addition products in low to good yields and low to moderate enantioselectivities. Collin and co-workers also expanded this methodology to the 1,4-addition of O-benzylhydroxylamine [245] (Scheme 37). Like the previous reactions, the

Synthesis of rigid p-terphenyl-linked carbohydrate mimetics

• Maja Kandziora and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2014, 10, 1749–1758, doi:10.3762/bjoc.10.182

• -couplings to form biphenyl aminopyran or p-terphenyl-linked dimers. Hydrogenolysis afforded new unnatural aminosugar mimetics. Zinc in the presence of acid or samarium diiodide were examined for the N–O bond cleavage in order to obtain the rigid p-terphenyl-linked C-glycosyl dimers. Keywords: carbohydrate

• mimetics; hydrogenolysis; multivalent glycosystems; 1,2-oxazines; samarium diiodide; Suzuki cross-coupling; Introduction Carbohydrates are the class of biomolecules with the highest structural diversity [1][2]. Specific carbohydrates are responsible for cell-type specific interactions [3] and they are

• into 22 long reaction times were required and the high acidity led to the formation of side products. Nevertheless, the target compound 22 was isolated in a moderate yield of 59%. As a milder alternative, samarium diiodide was examined for the N–O bond cleavage [40][41][42][43][44][45]. With this

Development of an additive-controlled, SmI₂-mediated stereoselective sequence: Telescoped spirocyclisation, lactone reduction and Peterson elimination

• Brice Sautier,
• Karl D. Collins and
• David J. Procter

Beilstein J. Org. Chem. 2013, 9, 1443–1447, doi:10.3762/bjoc.9.163

• Peterson elimination. The approach allows functionalised cyclopentanols containing two vicinal quaternary stereocentres to be conveniently prepared from simple starting materials. Keywords: cyclisation; free radical; Peterson elimination; reduction; samarium; telescoped process; Introduction Samarium

• more reducing system would tolerate the presence of samarium(III) salts and a less-activating additive (MeOH) from the first reduction step. Pleasingly, when subjected to the telescoped sequence, substrates 1 gave the desired triols 3 in comparable yields to those obtained from the stepwise process

Copper(II)-salt-promoted oxidative ring-opening reactions of bicyclic cyclopropanol derivatives via radical pathways

• Eietsu Hasegawa,
• Minami Tateyama,
• Ryosuke Nagumo,
• Eiji Tayama and
• Hajime Iwamoto

Beilstein J. Org. Chem. 2013, 9, 1397–1406, doi:10.3762/bjoc.9.156

• hexenyl radical cyclization reactions [21], (Figure 1) [22][23][24][25][26][27][28][29][30]. For example, PET reactions of probe I with amines were observed to produce a spirocyclic ketone product while its reduction reaction induced by samarium diiodide (SmI2) gives rise to a cyclopropanol (left in

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225

Synthesis of chiral sulfoximine-based thioureas and their application in asymmetric organocatalysis

• Marcus Frings,
• Isabelle Thomé and
• Carsten Bolm

Beilstein J. Org. Chem. 2012, 8, 1443–1451, doi:10.3762/bjoc.8.164

• reduce the α-nitro group of (R)-7 to the corresponding amino substituent (as in (R)-8) failed [58]. None of the reductive conditions, which included (1) hydrogenation over palladium/charcoal, (2) applying samarium diiodide with methanol as proton source, and (3) using a combination of zinc powder with

Carbohydrate-auxiliary assisted preparation of enantiopure 1,2-oxazine derivatives and aminopolyols

• Marcin Jasiński,
• Dieter Lentz and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2012, 8, 662–674, doi:10.3762/bjoc.8.74

• samarium diiodide leading to enantiopure acyclic aminopolyols. We also report on our attempts to convert these compounds into enantiopure hydroxylated pyrrolidine derivatives. Keywords: aminopolyols; carbohydrates; chiral auxiliaries; lithiated alkoxyallenes; 1,2-oxazines; pyrroles; pyrrolidines; samarium

• samarium diiodide-induced reactions, are presented as well. Results and Discussion In continuation of our recent exploration of L-erythrose-derived nitrones for the synthesis of 3,6-dihydro-2H-1,2-oxazine derivatives [34], we turned our attention to benzaldehyde-derived nitrone 1a, which is readily

• type 12 contain a benzylamine substructure, standard methods that may possibly attack this moiety, such as catalytic hydrogenation, should be avoided. As an alternative, samarium diiodide is an attractive reagent for this purpose. Apart from its extraordinary potential for the formation of new carbon

Syntheses and applications of furanyl-functionalised 2,2’:6’,2’’-terpyridines

• Jérôme Husson and
• Michael Knorr

Beilstein J. Org. Chem. 2012, 8, 379–389, doi:10.3762/bjoc.8.41

• then converted to an amine function by reduction with BH3. Subsequent treatment with tert-butyl bromoacetate afforded amino esters 53 and 54. Ester groups of compound 53 were then hydrolyzed to the free acids to afford 55. The latter was then reacted with europium(III) or samarium(III) chlorides to

• . Synthesis of tpy by Stille cross-coupling reaction. Oxidation of the furan ring of furanyl-substituted terpyridines. Direct oxidation of a furan ring attached on Ru(II) tpy complexes. Synthetic pathway to europium(III) and samarium(III) chelates 56 and 57. Synthetic pathway to prepare thiocyanato