Application of N-heterocyclic carbene–Cu(I) complexes as catalysts in organic synthesis: a review

• Nosheen Beig,
• Varsha Goyal and
• Raj K. Bansal

Beilstein J. Org. Chem. 2023, 19, 1408–1442, doi:10.3762/bjoc.19.102

• alkynes with silanes/t-BuOH and HBP, respectively. The Cu(I) complexes of five-, six-, and seven-membered NHCs were prepared through protonolysis of NHC–CuMes with t-BuOH (Scheme 63). Increasing the size of the heterocyclic ring was accompanied by higher selectivity to give mainly (Z)-alkenes and α

Modular synthesis of 2-furyl carbinols from 3-benzyldimethylsilylfurfural platforms relying on oxygen-assisted C–Si bond functionalization

• Sebastien Curpanen,
• Per Reichert,
• Gabriele Lupidi,
• Giovanni Poli,
• Julie Oble and
• Alejandro Perez-Luna

Beilstein J. Org. Chem. 2022, 18, 1256–1263, doi:10.3762/bjoc.18.131

• -catalyzed arylation reactions (Scheme 7). Fluoride-promoted arylation reactions of benzyldimethyl(alkenyl)silanes have been reported, and it is established that they proceed through the cleavage of the benzyl moiety from the benzyldimethylsilyl groups, leading to either dimethylsilanols or cyclic siloxanes

• requirement for copper prompted us to test copper-catalyzed C(sp2)–C(sp3) cross-coupling reactions, as reported by Takeda et al., to achieve allylation reactions of benzyldimethyl(alkenyl)silanes [36]. Treatment of 4c with methallyl chloride in the presence of TBAF⋅(t-BuOH)4 (2.4 equiv), CuI (1.5 equiv), and

Iron-catalyzed domino coupling reactions of π-systems

• Austin Pounder and
• William Tam

Beilstein J. Org. Chem. 2021, 17, 2848–2893, doi:10.3762/bjoc.17.196

• radical under aerobic conditions. Tandem attack on the alkenyl π-system with the sulfonyl radical followed by radical cyclization with the aryl ring constructs the substituted oxindoles 90. In 2017, Song and Li reported an oxidative spriocyclization of N‐arylpropiolamides 91 with silanes 92 for the

• variety of electron-donating and electron-withdrawing groups, though bulky silanes 92 afforded the products in reduced yield. The reaction proceeds through the formation of a silicon-centered radical generated via a Fe redox cycle (vide supra). Sequential attack on the alkenyl π-system followed by radical

• generating a benzylic radical which can be oxidized by Ag(I) to afford the corresponding benzylic cation. Nucleophilic trapping with an amine will produce the final product. In the same year, Song and co-workers reported a dehydrogenative 1,2-difunctionalization of conjugated alkenes 107 with silanes 92 and

Synthetic strategies toward 1,3-oxathiolane nucleoside analogues

• Umesh P. Aher,
• Dhananjai Srivastava,
• Girij P. Singh and
• Jayashree B. S

Beilstein J. Org. Chem. 2021, 17, 2680–2715, doi:10.3762/bjoc.17.182

Photoredox catalysis in nickel-catalyzed C–H functionalization

• Lusina Mantry,
• Rajaram Maayuri,
• Vikash Kumar and
• Parthasarathy Gandeepan

Beilstein J. Org. Chem. 2021, 17, 2209–2259, doi:10.3762/bjoc.17.143

• , ketones and silanes were also found to be compatible to give the desired three-component coupling products. Similarly, the scope of aryl bromides 3 and alkenes 92 were found to be broad. A possible catalytic cycle was proposed to account for the mechanism of the reaction (Figure 22) [140]. Photoexcited

Catalyzed and uncatalyzed procedures for the syntheses of isomeric covalent multi-indolyl hetero non-metallides: an account

• Ranadeep Talukdar

Beilstein J. Org. Chem. 2021, 17, 2102–2122, doi:10.3762/bjoc.17.137

• broad applications in organic electroluminescent devices [44]. Silanes Heteroaryl compounds containing silicon, an earth abundant and non-toxic element, are important in organic electronics or photonics and in the field of drug discovery and nuclear medicine [45][46][47][48][49][50]. The first property

• )silane 38 that involved n-BuLi as the base [58]. The strategy was later adopted by Ohshita in 2004 (40a, Scheme 6) [59]. Between 2016 and 2018, some acid-catalyzed syntheses of bis(indol-3-yl)silanes appeared [60][61][62][63]. Chen and co-workers demonstrated a Brønsted acid-catalyzed Friedel–Crafts

• ). A repetition of the processes leads to the bis(indol-3-yl)silanes 40. Han described a Lewis acid-promoted C3-silylation of N-protected substituted indoles by a disproportionation mechanism of the latter. He used both B(C6F5)3 and Al(C6F5)3 in the reactions (Scheme 8a and Scheme 8c) which followed a

Methodologies for the synthesis of quaternary carbon centers via hydroalkylation of unactivated olefins: twenty years of advances

• Thiago S. Silva and
• Fernando Coelho

Beilstein J. Org. Chem. 2021, 17, 1565–1590, doi:10.3762/bjoc.17.112

• of MHAT reactions is the high tolerance to the presence of other functional groups in the reactants due to the mild conditions usually employed. At the end of the 1980s and the middle of the 1990s, Mukaiyama published a series of seminal works reporting the use of silanes as reducing agents (hydride

Direct synthesis of anomeric tetrazolyl iminosugars from sugar-derived lactams

• Michał M. Więcław and
• Bartłomiej Furman

Beilstein J. Org. Chem. 2021, 17, 115–123, doi:10.3762/bjoc.17.12

• formamides [11] and reduction of isothiocyanates to thioformamides [12] by its means. There have also been some catalytic protocols developed for the reduction of amides to imines. The most notable examples incorporate iridium complexes and silanes [13][14]. Cheng and Brookhart showed that the chlorobis

Activation of pentafluoropropane isomers at a nanoscopic aluminum chlorofluoride: hydrodefluorination versus dehydrofluorination

• Maëva-Charlotte Kervarec,
• Thomas Braun,
• Mike Ahrens and
• Erhard Kemnitz

Beilstein J. Org. Chem. 2020, 16, 2623–2635, doi:10.3762/bjoc.16.213

• to accomplish the activation of 10a, it was of interest to introduce a silane, because as mentioned above, recent reports showed that the activation of various substrates treated with ACF was indeed promoted by the presence of silanes [16][39][47]. Thus, the experiments were also conducted in the

• at an ACF surface [39][47]. In addition, silylium species that are stabilized by weakly coordinating anions can also catalyze hydrodefluorination reactions in a homogeneous phase with silanes as hydrogen source [54][55][56][57]. In contrast, silylium-mediated dehydrofluorination reactions have not

Recent developments in enantioselective photocatalysis

• Callum Prentice,
• James Morrisson,
• Andrew D. Smith and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2020, 16, 2363–2441, doi:10.3762/bjoc.16.197

• = 0.22), so a chain mechanism is likewise unlikely. Interestingly, Melchiorre later found that with α-amino silanes 60, no photocatalyst was required (Scheme 8) [41]. This was proposed to be due to the formation of an intramolecular EDA complex, which upon excitation can form cation 61+ that can

• iminium ions 66 can be excited directly without formation of an EDA complex (Scheme 9a) [42]. The excited state iminium ion 66* can oxidise silanes 67 via a SET process to give radical cation 67•+ and alkyl radical 66•. Loss of the TMS group generates alkyl radicals 67• that can couple with 66

When metal-catalyzed C–H functionalization meets visible-light photocatalysis

• Lucas Guillemard and
• Joanna Wencel-Delord

Beilstein J. Org. Chem. 2020, 16, 1754–1804, doi:10.3762/bjoc.16.147

• aromatic coupling partner, including frequently used Weinreb amides or functionalized secondary and primary amides. Regarding the scope of olefin substrates, the reaction tolerated numerous functional groups including acrylates, vinyl silanes or sulfones which was interesting from the post

Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis

• Stephanie G. E. Amos,
• Marion Garreau,
• Luca Buzzetti and
• Jerome Waser

Beilstein J. Org. Chem. 2020, 16, 1163–1187, doi:10.3762/bjoc.16.103

Recent advances in Cu-catalyzed C(sp³)–Si and C(sp³)–B bond formation

• Balaram S. Takale,
• Ruchita R. Thakore,
• Elham Etemadi-Davan and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2020, 16, 691–737, doi:10.3762/bjoc.16.67

• reagent (7), to successfully convert benzyl phosphate 6 to benzylic silanes 8. Curiously, the reaction proceeded even in the absence of a ligand, albeit with lower yield (25%; Scheme 3). However, only one example was reported and a more general method for the preparation of alkylsilanes was developed by

• by Oestreich [29] for the synthesis of secondary (26–28) and tertiary (29) silanes via a radical pathway, in good chemical yields (Scheme 6). It was possible to perform this reaction on a wide array of alkyl iodides using various silylating reagents. One selected application of this reaction, which

• -containing products (166) was carried out to arrive at the keto phenol derivative 167. Loh, Xu, and co-workers [66] explored related reactions involving unsaturated ketimines using copper triflate or copper bis(4-cyclohexylbutyrate) (Cu(CHB)2) to prepare allylic silanes. Interestingly, using one or the other

Application of olefin metathesis in the synthesis of functionalized polyhedral oligomeric silsesquioxanes (POSS) and POSS-containing polymeric materials

• Patrycja Żak and
• Cezary Pietraszuk

Beilstein J. Org. Chem. 2019, 15, 310–332, doi:10.3762/bjoc.15.28

• reactivity is the inactivity of vinylsilsesquioxane in homometathesis. The limitations apply to silanes containing a double bond located directly at the silyl group and do not apply to allylsilanes and other alkenylsilanes, which behave like terminal olefins and readily undergo metathesis. Application of

Silanediol versus chlorosilanol: hydrolyses and hydrogen-bonding catalyses with fenchole-based silanes

• Falco Fox,
• Jörg M. Neudörfl and
• Bernd Goldfuss

Beilstein J. Org. Chem. 2019, 15, 167–186, doi:10.3762/bjoc.15.17

• ]) of the transition structure (TS) for the hydrolysis of dichlorosilane 7, 8, 13, [CH2O]2SiCl2 and SiCl4 to the corresponding mono- and diols. Computeda stretching frequencies (ν [cm−1]), lp···σ* [kcal mol−1] and donor acceptor distances (D [Å]) of silanes 7, 8, [CH2O]2SiCl(OH), [CH2O]2Si(OH)2, (OH

Organometallic vs organic photoredox catalysts for photocuring reactions in the visible region

• Aude-Héloise Bonardi,
• Frédéric Dumur,
• Guillaume Noirbent,
• Jacques Lalevée and
• Didier Gigmes

Beilstein J. Org. Chem. 2018, 14, 3025–3046, doi:10.3762/bjoc.14.282

• catalyst can react through an oxidative or a reductive cycle as presented in Figure 1. Herein, we will present four additives that can be used in combination with a photoredox catalyst to initiated photopolymerization (Scheme 1). As reduction agent, silanes such as tris(trimethylsilyl)silane (abbreviated

A selective removal of the secondary hydroxy group from ortho-dithioacetal-substituted diarylmethanols

• Anna Czarnecka,
• Emilia Kowalska,
• Agnieszka Bodzioch,
• Joanna Skalik,
• Marek Koprowski,
• Krzysztof Owsianik and
• Piotr Bałczewski

Beilstein J. Org. Chem. 2018, 14, 1229–1237, doi:10.3762/bjoc.14.105

• reagent [31], PBr3 [32], BF3·Et2O–dibutyl ether [33] and silanes (Si–H) in the presence of various Lewis acids: B(C6F5)3 [34][35][36], InCl3 [37][38], H3[PW12O40]×nH2O [39], Ca(NTf2)2 [40], Bi(OTf)3 [41], Sn(IV)-montmorillonite [42] and PdCl2 [43]. It is interesting that Seto et al. reported that Et3SiH

Recent advances in synthetic approaches for medicinal chemistry of C-nucleosides

• Kartik Temburnikar and
• Katherine L. Seley-Radtke

Beilstein J. Org. Chem. 2018, 14, 772–785, doi:10.3762/bjoc.14.65

• ) results in an oxocarbenium ion [62][70][80][81][82][83]. Reduction of this intermediate by various silanes gives C-nucleosides resembling the canonical nucleosides [82][83]. The stereochemical fate of oxocarbenium ion reduction is dictated by the conformation and stability of the oxocarbenium ion, which

Synthesis of substituted Z-styrenes by Hiyama-type coupling of oxasilacycloalkenes: application to the synthesis of a 1-benzoxocane

• James R. Vyvyan,
• Courtney A. Engles,
• Scott L. Bray,
• Erik D. Wold,
• Christopher L. Porter and
• Mikhail O. Konev

Beilstein J. Org. Chem. 2017, 13, 2122–2127, doi:10.3762/bjoc.13.209

• ]. Developed somewhat later than the aforementioned methods and the couplings of organomagnesium and organotin reagents was the cross-coupling of silanes, pioneered by Hiyama [3][4] and siloxanes [5]. This versatile method has been extensively reviewed [6][7][8]. The cross-coupling of alkenyl silanols [9][10

Phenylsilane as an effective desulfinylation reagent

• Wanda H. Midura,
• Aneta Rzewnicka and
• Jerzy A. Krysiak

Beilstein J. Org. Chem. 2017, 13, 1513–1517, doi:10.3762/bjoc.13.150

• methodology [10][11][12][13][14]. Besides the well-known metal-catalyzed hydrosilylation, transition metals in the presence of Brønsted or Lewis acids were used for the reduction. Recently base-activated silanes were also used for this purpose [15][16][17]. Results and Discussion Our recent investigations

(Z)-Selective Takai olefination of salicylaldehydes

• Stephen M. Geddis,
• Caroline E. Hagerman,
• Warren R. J. D. Galloway,
• Hannah F. Sore,
• Jonathan M. Goodman and
• David R. Spring

Beilstein J. Org. Chem. 2017, 13, 323–328, doi:10.3762/bjoc.13.35

• to generate vinyl stannanes [3], silanes [4] and boronates [5]. One of the most significant features of the Takai olefination is that it is generally highly selective for the formation of (E)-alkenes ((E):(Z)-product ratios are typically around 4:1 or greater). This selectivity has found wide use

Orthogonal protection of saccharide polyols through solvent-free one-pot sequences based on regioselective silylations

• Serena Traboni,
• Emiliano Bedini and
• Alfonso Iadonisi

Beilstein J. Org. Chem. 2016, 12, 2748–2756, doi:10.3762/bjoc.12.271

• ][21]. The protection generally takes several hours and the work-up is burdened by necessary removal of the high boiling solvent. A good regioselective control was also reported in an alternative silylation approach based on a dehydrogenative mechanism in which expensive trialkyl silanes were used as

Catalytic Wittig and aza-Wittig reactions

• Zhiqi Lao and
• Patrick H. Toy

Beilstein J. Org. Chem. 2016, 12, 2577–2587, doi:10.3762/bjoc.12.253

• covers the field of related catalytic aza-Wittig reactions that are catalyzed by both phosphine oxides and phosphines. Keywords: aza-Wittig reactions; catalysis; phosphines; phosphine oxides; reduction; silanes; Wittig reactions; Introduction The Wittig reaction is a venerable transformation for

• this regard it is encouraging that a life cycle assessment indicates that the use of stoichiometric quantities of silanes as replacements for phosphines in catalytic Wittig reactions can offer environmental improvements [41]. Thus it seems somewhat reasonable to expect that as even more efficient

Preparative semiconductor photoredox catalysis: An emerging theme in organic synthesis

• David W. Manley and
• John C. Walton

Beilstein J. Org. Chem. 2015, 11, 1570–1582, doi:10.3762/bjoc.11.173

• alkylations of alkenes with silanes [66] and thiols [67]. TiO2 reduction of a nitrochromenone derivative [70]. TiO2 mediated hydrodehalogenations and cyclizations of organic iodides [71]. TiO2 promoted hydrogenations of maleimides, maleic anhydride and aromatic aldehydes [79]. Mechanistic sketch of SCPC

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

• , and easy to handle. Though organosilicon reagents have been used in rhodium-catalyzed asymmetric 1,4-additions, many of them rely on the use of moisture-sensitive organotri(alkoxy)silanes or the addition of an acid or base in order to obtain the product in high yield and enantioselectivity [154