Advancements in hydrochlorination of alkenes

• Daniel S. Müller

Beilstein J. Org. Chem. 2024, 20, 787–814, doi:10.3762/bjoc.20.72

• chemistry textbooks as an exemplification of the Markovnikov rule. However, the application of this reaction is typically limited to specific alkenes, such as highly substituted ones, styrenes, or strained systems. Conversely, monosubstituted or 1,2-disubstituted alkenes do not readily react with HCl gas or

• hydrochlorinations, followed by metal-promoted radical hydrochlorinations, and concludes with a brief overview of recent anti-Markovnikov hydrochlorinations. Keywords: addition reactions; alkenes; alkyl chlorides; hydrochlorination; Markovnikov; Introduction The hydrochlorination of alkenes dates back to its

• discovery by Markovnikov in 1869, who formulated the "Markovnikov rule" as follows: "Experience shows that the halide adds to the least hydrogenated carbon, that is, to the one most susceptible to the influence of other carbon units” [1][2]. In the 1960s and 1970s, various research groups conducted detailed

A laterally-fused N-heterocyclic carbene framework from polysubstituted aminoimidazo[5,1-b]oxazol-6-ium salts

• Andrew D. Gillie,
• Matthew G. Wakeling,
• Bethan L. Greene,
• Louise Male and
• Paul W. Davies

Beilstein J. Org. Chem. 2024, 20, 621–627, doi:10.3762/bjoc.20.54

• ], intramolecular cyclisation [36] or a mixture of both [8][37][38][39]. The new ligand system proved to deliver competent catalysis. Conversion was seen in all cases at 1 mol % catalyst loading (Scheme 3). Use of 13 resulted in a slight increase of the anti-Markovnikov hydration product 17 over 18 when compared to

1-Butyl-3-methylimidazolium tetrafluoroborate as suitable solvent for BF₃: the case of alkyne hydration. Chemistry vs electrochemistry

• Marta David,
• Elisa Galli,
• Richard C. D. Brown,
• Marta Feroci,
• Fabrizio Vetica and
• Martina Bortolami

Beilstein J. Org. Chem. 2023, 19, 1966–1981, doi:10.3762/bjoc.19.147

• well-known and useful reaction in organic chemistry, affording carbonyl compounds based on an atom-economical approach. Indeed, the addition of water to the triple bond of a terminal alkyne leads to the formation of the corresponding methyl ketone or aldehyde, in the case of Markovnikov or anti

• -Markovnikov addition, respectively. On the other hand, the hydration of an internal unsymmetrical alkyne can lead to the formation of the two possible regioisomeric ketones. The hydration reaction requires a catalytic species, able to polarize the alkyne triple bond to facilitate water attack. Initially, in

• diphenylacetylene (1a), affording the corresponding ketones in high yields after 5 h. Otherwise, terminal alkynes generally showed higher reactivity compared to internal ones. For all the studied terminal alkynes, only ketone products (Markovnikov) were obtained, excluding the formation of the anti-Markovnikov ones

Radical chemistry in polymer science: an overview and recent advances

• Zixiao Wang,
• Feichen Cui,
• Yang Sui and
• Jiajun Yan

Beilstein J. Org. Chem. 2023, 19, 1580–1603, doi:10.3762/bjoc.19.116

• catalyst to produce radicals at the 2- and 5-positions of thiophene and synthesized four types of poly(3-alkylthiophene)s (PATs) with different linking ways (Scheme 10). 2.2 Polymerization by thiol–ene chemistry The thiol–ene reaction (also called alkene hydrothiolation) is the anti-Markovnikov addition of

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

• , the Cu complex derived from salt 166 was found to be most effective (Scheme 65) [87]. Jones and co-workers [88] developed a highly Markovnikov-selective hydroboration of alkenes and alkynes catalyzed by NHC–CuOH (Scheme 66). The products were obtained in high yields with low (0.5 mol %) catalyst

Photoredox catalysis harvesting multiple photon or electrochemical energies

• Mattia Lepori,
• Simon Schmid and
• Joshua P. Barham

Beilstein J. Org. Chem. 2023, 19, 1055–1145, doi:10.3762/bjoc.19.81

Pyridine C(sp²)–H bond functionalization under transition-metal and rare earth metal catalysis

• Haritha Sindhe,
• Malladi Mounika Reddy,
• Karthikeyan Rajkumar,
• Akshay Kamble,
• Amardeep Singh,
• Anand Kumar and
• Satyasheel Sharma

Beilstein J. Org. Chem. 2023, 19, 820–863, doi:10.3762/bjoc.19.62

• sterically bulky additive MAD coordinates to the pyridine nitrogen, which pushes the tethered alkene close to the nickel center subsequently providing the intermediate 201. Then, the C–D bond on cleavage via oxidative addition of Ni(0) forms the Ni–D species 202 which after anti-Markovnikov hydronickelation

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

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

• gold(III) salt AuCl3 nor the silver additive AgOTf was able to catalyze the reaction alone under the screened conditions. At elevated temperatures, however, the authors found that inter- and intramolecular olefin hydroalkylations occurred using AgOTf alone as the catalyst, leading to Markovnikov

• atom to olefins produces a higher substituted carbon radical (Markovnikov addition), making MHAT methodologies especially useful for quaternary carbon center synthesis. One of the first examples of MHAT use in quaternary carbon center construction was the use of vitamin B12 (cobalamin) [70] as a

• Markovnikov-type addition to generate a carbon-centered radical (B) that attacks the electron-deficient olefin (Scheme 22A). The newly formed alkyl radical (C) is then reduced by a Fe(II) species to an enolate (D) in an electron transfer (ET) step; a proton abstraction then delivers the hydroalkylated product

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

Metal-free visible-light-enabled vicinal trifluoromethyl dithiolation of unactivated alkenes

• Xiaojuan Li,
• Qiang Zhang,
• Weigang Zhang,
• Jinzhu Ma,
• Yi Wang and
• Yi Pan

Beilstein J. Org. Chem. 2021, 17, 551–557, doi:10.3762/bjoc.17.49

• -Markovnikov hydrotrifluoromethylthiolation of alkenes utilizing trifluoromethanesulfonic anhydride (Tf2O) as a radical trifluoromethylthiolating reagent through a deoxygenative reduction and a photoredox radical pathway (Scheme 1b). The C–S bond [44][45] is an important structural motif that is widely present

CF₃-substituted carbocations: underexploited intermediates with great potential in modern synthetic chemistry

• Anthony J. Fernandes,
• Armen Panossian,
• Bastien Michelet,
• Agnès Martin-Mingot,
• Frédéric R. Leroux and
• Sébastien Thibaudeau

Beilstein J. Org. Chem. 2021, 17, 343–378, doi:10.3762/bjoc.17.32

Reactions of 3-aryl-1-(trifluoromethyl)prop-2-yn-1-iminium salts with 1,3-dienes and styrenes

• Thomas Schneider,
• Michael Keim,
• Bianca Seitz and
• Gerhard Maas

Beilstein J. Org. Chem. 2020, 16, 2064–2072, doi:10.3762/bjoc.16.173

• (Markovnikov-type addition) at the olefinic bond of the styrene to form the resonance-stabilized benzyl cation 14 which can add intramolecularly to the nucleophilic central carbon atom of the aminoallene moiety, either by an electrophilic 1,4-cyclization yielding a cyclobutene 15 or by an 1,6-cyclization

Pauson–Khand reaction of fluorinated compounds

• Jorge Escorihuela,
• Daniel M. Sedgwick,
• Alberto Llobat,
• Mercedes Medio-Simón,
• Pablo Barrio and
• Santos Fustero

Beilstein J. Org. Chem. 2020, 16, 1662–1682, doi:10.3762/bjoc.16.138

• which they detailed the Markovnikov hydrofluorination of alkynes using HF.DMPU coupled with a gold catalyst [60]. Accordingly, the appropriate propargylmalonate derivatives were fluorinated to give fluoroalkene intermediates, which were then converted into malonate-based enynes 37 (Z = CO2R) through a

An overview on disulfide-catalyzed and -cocatalyzed photoreactions

• Yeersen Patehebieke

Beilstein J. Org. Chem. 2020, 16, 1418–1435, doi:10.3762/bjoc.16.118

• excellent radical properties also made these thiyl radicals powerful HAT catalysts. They have increasingly been proven useful in various types of organic photoreactions, such as cyclizations, anti-Markovnikov additions, aromatic olefin carbonylations, isomerizations, etc. They are a class of green, economic

• variety of reactions, renders them a class of green, economic, mild, and chemoselective radical catalyst. Apart from this, they are also excellent HAT catalysts in photoredox catalysis systems [2][3]. In various types of organic photochemistry reactions, such as cyclizations, anti-Markovnikov additions

• synthesize alcohols, and realizing the anti-Markovnikov regioselectivity is extremely challenging. In 2017, Lei and co-workers reported a class of disulfide-cocatalyzed anti-Markovnikov olefin hydration reactions [24]. In this reaction, 9-mesityl-10-methylacridinium (Acr+–Mes–ClO4−) and diphenyl disulfide

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

• fragmentation is not favored, these charged radicals can be intercepted and lead to different selectivities when compared to a traditional two-electron chemistry (e.g., anti-Markovnikov vs Markovnikov or ipso-SNAr reactions). Heteroatom-containing radical anions, such as ketyl radicals, constitute a special

• radical anions or their equivalents with other heteroatoms. However, organophotocatalysts have been only rarely used for this type of reduction. C2-charged radical species Since 2013, the Nicewicz group has developed a multitude of methodologies for the anti-Markovnikov hydrofunctionalization of alkenes

• alkyl group (Me in OD2) to an aryl group (Ph in OD3), they could limit the photocatalyst bleaching due to the demethylation of the organic dye. Alkene radical anions have been less exploited than their cationic equivalents. In 2017, the Lei group developed a Markovnikov-selective hydrosulfonylation

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

• alkene 307 (e.g., protected allylic alcohols) was explored by varying the ligand on copper. Using catalytic CuCl/Xantphos, direct access to anti-Markovnikov alkylborated products (e.g., 353, 354) was noted. Alternatively, simply switching from Xantphos to Cy-Xantphos afforded the products of Markovnikov

Synthesis of the aglycon of scorzodihydrostilbenes B and D

• Katja Weimann and
• Manfred Braun

Beilstein J. Org. Chem. 2019, 15, 610–616, doi:10.3762/bjoc.15.56

• particularly attractive as it leads in an atom-economic manner directly to the carbon skeleton of scorzodihydrostilbenes, starting from suitably substituted acetophenone and styrene derivatives. Furthermore, Murai’s protocol offers another advantage: the regioselective formation of the anti-Markovnikov product

N-Arylphenothiazines as strong donors for photoredox catalysis – pushing the frontiers of nucleophilic addition of alcohols to alkenes

• Fabienne Speck,
• David Rombach and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2019, 15, 52–59, doi:10.3762/bjoc.15.5

• insufficient reduction potential of the photoredox catalyst, the Markovnikov addition of alcohols through oxidative quenching is yet limited to highly activated, aromatic alkenes. To the best of our knowledge no methods are known today that allow the addition of alcohols to α-methyl-substituted styrenes

• -phenylphenothiazine derivatives 1–11 as photoredox catalysts. Three of them were identified to be highly suitable for the addition of methanol to alkenes affording the corresponding Markovnikov products. Results and Discussion Activated aromatic olefins, such as 1,1-diphenylethylene (12), have reduction potentials

Cobalt bis(acetylacetonate)–tert-butyl hydroperoxide–triethylsilane: a general reagent combination for the Markovnikov-selective hydrofunctionalization of alkenes by hydrogen atom transfer

• Xiaoshen Ma and
• Seth B. Herzon

Beilstein J. Org. Chem. 2018, 14, 2259–2265, doi:10.3762/bjoc.14.201

• -butyl hydroperoxide (TBHP), and triethylsilane (Et3SiH) constitute an inexpensive, general, and practical reagent combination to initiate a broad range of Markovnikov-selective alkene hydrofunctionalization reactions. These transformations are believed to proceed by cobalt-mediated hydrogen atom

• reagent combination suggests it as a useful starting point to develop HAT reactions in complex settings. Keywords: HAT; hydrogen atom transfer; hydrofunctionalization; Introduction Many powerful methods to effect alkene hydrogenation [1][2][3][4] and Markovnikov-selective hydroheterofunctionalization (H

• formation of 4d represents the first Markovnikov-selective alkene hydrobromination by an HAT pathway. Attempts to extend this reaction to hydroiodination using related reagents, p-toluenesulfonyl iodide, N-iodosuccinimide, or molecular iodine failed to provide the expected product (see Supporting

A general and atom-efficient continuous-flow approach to prepare amines, amides and imines via reactive N-chloramines

• Katherine E. Jolley,
• Michael R. Chapman and
• A. John Blacker

Beilstein J. Org. Chem. 2018, 14, 2220–2228, doi:10.3762/bjoc.14.196

• further reactions. Reaction of N-chloramine with alkene Initially our study tested the reaction of N-chloromorpholine (16) to styrene (13) varying Cu catalyst loading and a range of temperatures. The anti-Markovnikov addition product was observed with 10% CuI catalyst loading, at ambient temperature

Hypervalent iodine compounds for anti-Markovnikov-type iodo-oxyimidation of vinylarenes

• Igor B. Krylov,
• Stanislav A. Paveliev,
• Mikhail A. Syroeshkin,
• Alexander A. Korlyukov,
• Pavel V. Dorovatovskii,
• Yan V. Zubavichus,
• Gennady I. Nikishin and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2018, 14, 2146–2155, doi:10.3762/bjoc.14.188

• -containing oxidative systems with the addition of various nucleophiles have been published, all of these processes have common mechanism and the same regioselectivity. The free-radical approach developed in the present work affords the opposite (anti-Markovnikov) regioselectivity of the addition to the

• for anti-Markovnikov type regioselectivity of C–O and C–I bond formation. Electrochemical mechanistic studies based on cyclic voltammetry (CV) data confirm proposed reaction mechanism. Possible ways of using the obtained iodo-oxyimidated products via substitution of iodine atom were demonstrated

Photocatalytic formation of carbon–sulfur bonds

• Alexander Wimmer and
• Burkhard König

Beilstein J. Org. Chem. 2018, 14, 54–83, doi:10.3762/bjoc.14.4

• ]. The thiyl radical was generated as reactive key intermediate from a variety of thiols by photooxidation using [Ru(bpz)3](PF6)2. Aliphatic and aromatic thiols react with aliphatic and aromatic alkenes and alkynes in high to excellent yields to the anti-Markovnikov addition adducts. However, an excess

• radical anion then deprotonates the thiyl radical cation. Subsequent addition to the alkene yields the anti-Markovnikov radical intermediate. Radical addition to dioxygen leads finally to the β-ketosulfide, which subsequently is oxidized by the in situ generated hydrogen peroxide radical to the respective

• . Radical addition to the alkyne leads to the anti-Markovnikov adduct via the more stable secondary radical intermediate. As alkyne 2-methyl-3-butyn-2-ol was selected, which is easily prepared from acetylene and acetone on large scale and the respective thiol–yne adducts can be converted into valuable

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation. Part 1: Use of CF₃SO₂Na

• Hélène Guyon,
• Hélène Chachignon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2764–2799, doi:10.3762/bjoc.13.272

• chalcone gave low regioselectivities with mixed Markovnikov and anti-Markovnikov products. The CF3 radical is electrophilic in nature and, as such, not prone to readily react with electron-deficient alkenes. Nevertheless, Lefebvre, Hoffmann and Rueping reported that N-substituted maleimides, maleic

• -Markovnikov selectivity. Notably, styrene failed to react under these conditions. A selection of α,β-unsaturated electron-withdrawing motifs that included a sulfone, esters, an amide, and a ketone were investigated for the first time and the β-addition products were obtained regioselectively in moderate to

Electrophilic trifluoromethylselenolation of terminal alkynes with Se-(trifluoromethyl) 4-methylbenzenesulfonoselenoate

• Clément Ghiazza,
• Anis Tlili and
• Thierry Billard

Beilstein J. Org. Chem. 2017, 13, 2626–2630, doi:10.3762/bjoc.13.260

• . Further, a high regioselectivity is observed but, surprisingly, the anti-Markovnikov regioisomers were obtained. The stereochemistry and regiochemistry were confirmed thanks to the X-ray structure of compound 3a (Figure 1). From a mechanistic point of view, the reaction starts certainly with the