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Search for "metal free" in Full Text gives 289 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.

C–H bond functionalization: recent discoveries and future directions

  • Indranil Chatterjee

Beilstein J. Org. Chem. 2023, 19, 1568–1569, doi:10.3762/bjoc.19.114

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  • its combination with organometallic chemistry for site-selective C−H bond functionalization [3][4]. Recent years have witnessed many viable strategies for the synthesis of complex targets utilizing photoredox catalysis, electroorganic catalysis, Lewis acid catalysis, and transition-metal-free
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Editorial
Published 17 Oct 2023

Morpholine-mediated defluorinative cycloaddition of gem-difluoroalkenes and organic azides

  • Tzu-Yu Huang,
  • Mario Djugovski,
  • Sweta Adhikari,
  • Destinee L. Manning and
  • Sudeshna Roy

Beilstein J. Org. Chem. 2023, 19, 1545–1554, doi:10.3762/bjoc.19.111

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  • Tzu-Yu Huang Mario Djugovski Sweta Adhikari Destinee L. Manning Sudeshna Roy Department of BioMolecular Sciences, School of Pharmacy, University of Mississippi, University, MS 38677, USA 10.3762/bjoc.19.111 Abstract Here, we report the first transition-metal-free defluorinative cycloaddition of
  • are typically accessed in two ways: (1) direct synthesis using metal or metal-free catalysis and (2) post-functionalization of disubstituted-1,2,3-triazoles [17][18]. The direct synthesis of fully substituted triazoles entails either metal-free carbonyl-based [19][20][21] or metal-mediated and strain
  • organic azides in morpholine as a solvent forming C-4-morpholine functionalized fully decorated 1,2,3-triazoles with potential applications in pharmaceutical, biomedical, agrichemical, and materials sciences. This study fills a critical gap in the literature as it is a transition-metal-free and
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Letter
Published 05 Oct 2023

N-Sulfenylsuccinimide/phthalimide: an alternative sulfenylating reagent in organic transformations

  • Fatemeh Doraghi,
  • Seyedeh Pegah Aledavoud,
  • Mehdi Ghanbarlou,
  • Bagher Larijani and
  • Mohammad Mahdavi

Beilstein J. Org. Chem. 2023, 19, 1471–1502, doi:10.3762/bjoc.19.106

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  • functional materials and indispensable synthetic intermediates in drug discovery [31][32][33]. Because of their value, constructing C–S bonds has attracted significant attention via metal-catalyzed cross-coupling reactions and metal-free C–S bond formation [34][35][36][37]. Direct sulfenylation of the C–H
  • 102 were obtained in moderate to excellent yields with good to excellent enantioselectivities (Scheme 42) [76]. It should be noted that the authors did not define the exact role of the organocatalyst in the reaction mechanism. Transition-metal-free C–H sulfenylation of electron-rich arenes 103 by N
  • . developed a metal-free procedure for the synthesis of functionalized alkynyl disulfides 149 and acyl disulfides 151 under acid catalysis (Scheme 64) [94]. In this regard, they used N-alkynylthiophthalimides in the reaction with thiols to make a series of bioactive disulfides. Various simple thiols, cystines
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Published 27 Sep 2023

Non-noble metal-catalyzed cross-dehydrogenation coupling (CDC) involving ether α-C(sp3)–H to construct C–C bonds

  • Hui Yu and
  • Feng Xu

Beilstein J. Org. Chem. 2023, 19, 1259–1288, doi:10.3762/bjoc.19.94

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  • attractive features of this approach. Li et al. reported a new strategy for a metal-free CDC alkylation under mild conditions using 2,3-butanedione (diacetyl) as the hydrogen atom abstractor to extrude a hydrogen from the ether substrate to generate the radical intermediate which affords the products (Scheme
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Published 06 Sep 2023
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  • various acids [49]. This system is completely metal-free and uses one photocatalyst rather than separate sensitizer and catalyst species. However, the electron source for the reductions was a thiolate sacrificial donor and not water. Thiolates are used as redox mediators in other systems such as dye
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Published 08 Aug 2023

Exploring the role of halogen bonding in iodonium ylides: insights into unexpected reactivity and reaction control

  • Carlee A. Montgomery and
  • Graham K. Murphy

Beilstein J. Org. Chem. 2023, 19, 1171–1190, doi:10.3762/bjoc.19.86

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  • elimination) more commonly associated with transition metal-mediated chemistry; however, halogen- or σ-hole bonding has recently emerged as a credible explanation for the diverse reactivity that iodonium ylides undergo. σ-Hole bonding theory offers a means to explain the occurrence of transition metal-free
  • ]. However, numerous inconsistencies have been observed when comparing the outcomes of diazo- and iodonium ylide-based metallocarbene reactions, especially during metal-free control experiments, which led researchers to propose alternative, carbene-free reaction pathways for iodonium ylides. This was first
  • reported by Hadjiarapoglou, Varvoglis and co-workers [107][108][109][110][111][112] and Moriarty et al. [113][114][115], who observed metal-free cycloadditions between iodonium ylides and olefins in the absence of a transition metal catalyst. These reactions proceeded under mild conditions without catalyst
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Published 07 Aug 2023

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

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Published 28 Jul 2023

Copper-catalyzed N-arylation of amines with aryliodonium ylides in water

  • Kasturi U. Nabar,
  • Bhalchandra M. Bhanage and
  • Sudam G. Dawande

Beilstein J. Org. Chem. 2023, 19, 1008–1014, doi:10.3762/bjoc.19.76

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  • , catalyzed by a copper catalyst [39]. Murphy and co-workers reported blue LED-mediated metal-free cyclopropanation of alkenes with iodonium ylides through a diradical intermediate [40]. However, iodonium ylides are relatively unexplored for the arylation of amines. So far only Spyroudis’s group reported N
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Published 04 Jul 2023

Clauson–Kaas pyrrole synthesis using diverse catalysts: a transition from conventional to greener approach

  • Dileep Kumar Singh and
  • Rajesh Kumar

Beilstein J. Org. Chem. 2023, 19, 928–955, doi:10.3762/bjoc.19.71

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  • process has many advantages because it is a metal-free, easy to use, and environmentally friendly method that also gives good product yields with a wide range of substrates. The deep eutectic solvent used in this protocol is cheap, reusable, non-toxic, and biodegradable. In this study, it was found that
  • of N-arylpyrroles from various amines 78 via the reaction with 2,5-dimethoxytetrahydrofuran (2). Oxone is a mild, inexpensive, nontoxic, stable, and transition-metal-free catalyst that is very easy to handle during this transformation and provided high yields of the product. The authors also proposed
  • (2). Further, a nucleophilic attack of amines 40 with intermediate A, MeOH removal, dehydration, and aromatization steps produce N-substituted pyrroles 41 in good to excellent yields. In 2019, Wani et al. [73] used the alkaline-earth metal-based catalyst Ca(NO3)2∙4H2O for a mild, transition metal
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Published 27 Jun 2023

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

Graphical Abstract
  • , diversely functionalized pyridines have been synthesized via C–H activation under transition-metal and rare earth metal catalysis, including C–H alkylation, alkenylation, arylation, heteroarylation, borylation, etc. Recently, metal-free approaches have also been developed for the C–H functionalization of N
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Published 12 Jun 2023

Photocatalytic sequential C–H functionalization expediting acetoxymalonylation of imidazo heterocycles

  • Deepak Singh,
  • Shyamal Pramanik and
  • Soumitra Maity

Beilstein J. Org. Chem. 2023, 19, 666–673, doi:10.3762/bjoc.19.48

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  • acetylating agent. The developed method is heavy-metal free, as shown by the use of inexpensive PTH, as well as a base-free approach, and involves aerial oxygen to generate exciting derivatives, which may prove to be valuable in the field of radical chemistry research in future. Strategies of C-3
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Published 12 May 2023

Direct C2–H alkylation of indoles driven by the photochemical activity of halogen-bonded complexes

  • Martina Mamone,
  • Giuseppe Gentile,
  • Jacopo Dosso,
  • Maurizio Prato and
  • Giacomo Filippini

Beilstein J. Org. Chem. 2023, 19, 575–581, doi:10.3762/bjoc.19.42

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  • and Technology Alliance (BRTA), Paseo de Miramón 194, 20014, Donostia San Sebastián, Spain Basque Fdn Sci, Ikerbasque, 48013 Bilbao, Spain 10.3762/bjoc.19.42 Abstract A light-driven metal-free protocol for the synthesis of sulfone-containing indoles under mild conditions is reported. Specifically
  • to photochemically generate electrophilic radicals that can drive the functionalization of suitable electron-rich substrates [23]. Exploiting this strategy, here we report a novel metal-free methodology for the direct homolytic aromatic substitution (HAS) reaction of indoles 1 with α-iodosulfones 2
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Published 27 Apr 2023

Transition-metal-catalyzed domino reactions of strained bicyclic alkenes

  • Austin Pounder,
  • Eric Neufeld,
  • Peter Myler and
  • William Tam

Beilstein J. Org. Chem. 2023, 19, 487–540, doi:10.3762/bjoc.19.38

Graphical Abstract
  • to domino reactions which include at least two distinct reactions. The review is divided on the basis of the transition-metal catalyst used in the reaction and will not cover metal-free methods. The literature is covered up to and including January 2023. For reasons of clarity, newly formed bonds are
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Published 24 Apr 2023

CuAAC-inspired synthesis of 1,2,3-triazole-bridged porphyrin conjugates: an overview

  • Dileep Kumar Singh

Beilstein J. Org. Chem. 2023, 19, 349–379, doi:10.3762/bjoc.19.29

Graphical Abstract
  • 85 and porphyrin-psoralen conjugate 87 could be potential candidates for PDT applications. Recently, Charisiadis et al. [45] explored this modular click chemistry protocol for the synthesis of a noble metal-free meso-triazole cobalt porphyrin diimine-dioxime conjugate 91 by covalently connecting a
  • Cheng [63] designed a click inspired synthesis of novel discotic mesogen bearing a porphyrin unit, a triazole linkage, and a peripheral 3,4,5-trialkoxybenzyl unit (Scheme 32). Firstly, free-base porphyrin conjugates 151a–c were obtained by the CuAAC reaction between metal free tetraalkynylporphyrin 149
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Published 22 Mar 2023

An efficient metal-free and catalyst-free C–S/C–O bond-formation strategy: synthesis of pyrazole-conjugated thioamides and amides

  • Shubham Sharma,
  • Dharmender Singh,
  • Sunit Kumar,
  • Vaishali,
  • Rahul Jamra,
  • Naveen Banyal,
  • Deepika,
  • Chandi C. Malakar and
  • Virender Singh

Beilstein J. Org. Chem. 2023, 19, 231–244, doi:10.3762/bjoc.19.22

Graphical Abstract
  • Department of Chemistry, Central University of Punjab, Bathinda, 151401, Punjab, India, Department of Chemistry, National Institute of Technology (NIT) Manipur, Imphal, 795004, India 10.3762/bjoc.19.22 Abstract An operationally simple and metal-free approach is described for the synthesis of pyrazole
  • , metal-free and easy to perform reaction conditions. Moreover, the pyrazole C-3/5-linked amide conjugates were also synthesized via an oxidative amination of pyrazole carbaldehydes and 2-aminopyridines using hydrogen peroxide as an oxidant. Keywords: C–S/O bond formation; metal-free; oxidative amidation
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Published 02 Mar 2023

NaI/PPh3-catalyzed visible-light-mediated decarboxylative radical cascade cyclization of N-arylacrylamides for the efficient synthesis of quaternary oxindoles

  • Dan Liu,
  • Yue Zhao and
  • Frederic W. Patureau

Beilstein J. Org. Chem. 2023, 19, 57–65, doi:10.3762/bjoc.19.5

Graphical Abstract
  • is mediated by visible light irradiation. A wide range of substrates bearing different substituents and derived from ubiquitous carboxylic acids, including α-amino acids, were synthesized and examined under this very mild, efficient, and cost effective transition-metal-free synthetic method. These
  • afforded various functionalized oxindoles featuring a C3 quaternary stereogenic center. Mechanistic experiments suggest a radical mechanism. Keywords: decarboxylative cascade cyclization; iodide catalysis; metal-free photocatalysis; oxindole; phosphine catalysis; Introduction Radical-initiated cascade
  • limited substrate scopes (Scheme 1a). With the rapid development of sustainable chemistry, developing low-cost and transition-metal-free photocatalytic methods has become a strategic priority. In 2019 [54], the groups of Fu and Shang pioneered the photocatalytic decarboxylative alkylation of silyl enol
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Published 16 Jan 2023

Two-step continuous-flow synthesis of 6-membered cyclic iodonium salts via anodic oxidation

  • Julian Spils,
  • Thomas Wirth and
  • Boris J. Nachtsheim

Beilstein J. Org. Chem. 2023, 19, 27–32, doi:10.3762/bjoc.19.2

Graphical Abstract
  • blocks for the synthesis of natural products [16][17][18][19][20][21]. One subclass of HVIs is diaryliodonium salts (DIS), which have been used as versatile electrophilic arylation reagents in metal-catalyzed and metal-free reactions [22][23]. The corresponding cyclic diaryliodonium salts (CDIS) have
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Published 03 Jan 2023

Redox-active molecules as organocatalysts for selective oxidative transformations – an unperceived organocatalysis field

  • Elena R. Lopat’eva,
  • Igor B. Krylov,
  • Dmitry A. Lapshin and
  • Alexander O. Terent’ev

Beilstein J. Org. Chem. 2022, 18, 1672–1695, doi:10.3762/bjoc.18.179

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  • include their synthetic availability, wide opportunities for rational structure design, generally lower toxicity, air and water stability, metal-free nature, and the scalability of their production and use. These features have made organocatalysis a prospering area and an even more promising methodology
  • in the case of chelating substrates [80]. In order to avoid the usage of transition metal salts, metal-free oxidative systems for the generation of imide-N-oxyl radicals were proposed. In the majority of such systems, an N-hydroxyimide undergoes single-electron oxidation photochemically by a
  • were used as redox-active organocatalysts for the oxidative coupling of aryl- and alkenylmagnesium compounds employing molecular oxygen as the terminal oxidant [154] (Scheme 38). Frustrated Lewis pairs (FLP) have gained much attention in the last decade due to unique reactivity, such as metal-free H2
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Published 09 Dec 2022

A novel bis-triazole scaffold accessed via two tandem [3 + 2] cycloaddition events including an uncatalyzed, room temperature azide–alkyne click reaction

  • Ksenia Malkova,
  • Andrey Bubyrev,
  • Vasilisa Krivovicheva,
  • Dmitry Dar’in,
  • Alexander Bunev and
  • Mikhail Krasavin

Beilstein J. Org. Chem. 2022, 18, 1636–1641, doi:10.3762/bjoc.18.175

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  • scaffolds. Recently, we reported a novel, metal-free synthesis of 1,5-disubstituted 1,2,3-triazoles via a three-component reaction of α-acetyl-α-diazomethanesulfonamide (1) with aldehydes and amines [4]. The reaction proceeded, presumably, through the formation of the initial 1,2,3-triazoline adduct 2 [5
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Published 02 Dec 2022

Functionalization of imidazole N-oxide: a recent discovery in organic transformations

  • Koustav Singha,
  • Imran Habib and
  • Mossaraf Hossain

Beilstein J. Org. Chem. 2022, 18, 1575–1588, doi:10.3762/bjoc.18.168

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  • , like cycloaddition, metal-free coupling reactions, three-component or multicomponent reactions etc., which use N-oxide chemistry. In 2021 Timofey D. Moseev and co-workers unfolded an attractive procedure of the coupling reaction between 2H-imidazole 1-oxides and polyphenols under metal-free conditions
  • the past years are discussed. This review contains cycloaddition reactions, nucleophilic halogenation reactions, metal-free coupling reactions, formation of N-heterocyclic carbenes, and multicomponent reactions, mainly three-component reactions. The mentioned methodologies have been performed by
  • substitution reactions Metal-free coupling reaction through nucleophilic substitution of H-atom (SNH) In 2020, a C–H/C–Li coupling reaction between 2H-imidazole 1-oxides and pentafluorophenyllithium under transition metal-free conditions was reported by Timofey D. Moseev and co-workers [17]. The reaction
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Published 22 Nov 2022

Dissecting Mechanochemistry III

  • Lars Borchardt and
  • José G. Hernández

Beilstein J. Org. Chem. 2022, 18, 1454–1456, doi:10.3762/bjoc.18.150

Graphical Abstract
  • were also key reagents to develop the mechanochemical halogenation of azobenzenes as studied by Ćurić and co-workers [4]. They demonstrated how, depending on the azobenzene structure, the halogenation of the C–H bonds with NBX occurred in the presence of Pd(II) catalysts or under metal-free conditions
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Editorial
Published 12 Oct 2022

Synthesis of meso-pyrrole-substituted corroles by condensation of 1,9-diformyldipyrromethanes with pyrrole

  • Baris Temelli and
  • Pinar Kapci

Beilstein J. Org. Chem. 2022, 18, 1403–1409, doi:10.3762/bjoc.18.145

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  • reaction conditions and catalysts, unidentified product mixtures were obtained instead of corrole products in both reactions. Then, the reaction of 1,9-diformyl-5-phenyldipyrromethane (1a) in an excess amount of pyrrole was tested to obtain pyrrole-substituted metal-free corrole through the oxidation of
  • production of mono pyrrole metal-free corrole compounds and the polymerization reactions of the obtained compounds are ongoing in our laboratory. Experimental General information All reactions were performed under N2 atmosphere. All reagents and solvents were of reagent grade. The NMR spectra were recorded
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Published 06 Oct 2022

B–N/B–H Transborylation: borane-catalysed nitrile hydroboration

  • Filip Meger,
  • Alexander C. W. Kwok,
  • Franziska Gilch,
  • Dominic R. Willcox,
  • Alex J. Hendy,
  • Kieran Nicholson,
  • Andrew D. Bage,
  • Thomas Langer,
  • Thomas A. Hunt and
  • Stephen P. Thomas

Beilstein J. Org. Chem. 2022, 18, 1332–1337, doi:10.3762/bjoc.18.138

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  • research into the development of new catalytic methodologies, specifically those that use Earth-abundant and low toxicity elements, as an alternative to transition-metal catalysis [9][10]. Using metal-free catalytic systems, including boron-based catalysts, circumvents some of the issues associated with
  • traditional metal catalysis, including trace metal contamination [11][12] and volatility of supply. Whilst there are several examples of main-group catalysed nitrile hydroboration reactions [13][14][15][16][17][18][19][20][21][22][23][24][25][26], currently, there are only two reported metal-free catalytic
  • nitriles with broad chemoselectivity, raise the standing of metal-free catalysis in nitrile hydroboration, and increase user accessibility by using commercially available catalysts and turnover reagents (Scheme 1b). Results and Discussion Investigations began by screening a combination of commercially
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Published 26 Sep 2022

Mechanochemical bottom-up synthesis of phosphorus-linked, heptazine-based carbon nitrides using sodium phosphide

  • Blaine G. Fiss,
  • Georgia Douglas,
  • Michael Ferguson,
  • Jorge Becerra,
  • Jesus Valdez,
  • Trong-On Do,
  • Tomislav Friščić and
  • Audrey Moores

Beilstein J. Org. Chem. 2022, 18, 1203–1209, doi:10.3762/bjoc.18.125

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  • minimize the bandgap of these metal-free photocatalysts, as well as improve their overall stability. Traditional routes to incorporate phosphorus have relied on high-temperature [7] or microwave [8] syntheses, and often proceed through the introduction of a phosphorus atom within the heptazine ring, which
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Published 12 Sep 2022

Derivatives of benzo-1,4-thiazine-3-carboxylic acid and the corresponding amino acid conjugates

  • Péter Kisszékelyi,
  • Tibor Peňaška,
  • Klára Stankovianska,
  • Mária Mečiarová and
  • Radovan Šebesta

Beilstein J. Org. Chem. 2022, 18, 1195–1202, doi:10.3762/bjoc.18.124

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  • a reversible acidochromic behavior [30]. Zhao et al. demonstrated a three-component transition-metal-free aerobic method using a KI/DMSO/O2 system for the facile generation of iminobenzo-1,4-thiazines in moderate to good yield [31]. 3,4-Dihydro-2H-benzo-1,4-thiazine derivatives 6 were also
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Published 09 Sep 2022
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