The LANCA three-component reaction to highly substituted β-ketoenamides – versatile intermediates for the synthesis of functionalized pyridine, pyrimidine, oxazole and quinoxaline derivatives

• Tilman Lechel,
• Roopender Kumar,
• Mrinal K. Bera,
• Reinhold Zimmer and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2019, 15, 655–678, doi:10.3762/bjoc.15.61

• ammonium salts or with hydroxylamine hydrochloride afford pyrimidines PM or pyrimidine N-oxides PO with a highly flexible substitution pattern in good yields. The functional groups of these heterocycles also allow a variety of subsequent reactions to various pyrimidine derivatives. On the other hand, acid

• acid treatment leads to acylamido-substituted 1,2-diketones DK that could be converted into quinoxalines QU. All classes of heterocycles accessed through the key β-ketoenamides show a unique substitution pattern – not easily accomplishable by alternative methods – and therefore many subsequent

• substitution pattern, the available pyrimidines PM contain a methyl group at C-4 and an alkoxy group OR1 at C-5. The remarkably wide scope of this pyrimidine synthesis is demonstrated by the thirty examples collected in Table 4. All tested β-ketoenamides were successfully converted into the pyrimidines PM and

Synthesis and fluorescent properties of N(9)-alkylated 2-amino-6-triazolylpurines and 7-deazapurines

• Andrejs Šišuļins,
• Jonas Bucevičius,
• Yu-Ting Tseng,
• Irina Novosjolova,
• Kaspars Traskovskis,
• Ērika Bizdēna,
• Huan-Tsung Chang,
• Sigitas Tumkevičius and
• Māris Turks

Beilstein J. Org. Chem. 2019, 15, 474–489, doi:10.3762/bjoc.15.41

• series possessing identical substitution pattern (structural congeners G and H, Figure 1). The easy access to the title compounds opened a possibility for a comparative study of their photophysical properties. Synthesis N(9)-Alkylated-2,6-diazidopurine 2a was synthesized in two steps from commercially

• biocompatible, cell-permeable, not cytotoxic and do not influence cell proliferation. Thus, one can predict that the developed purine and 7-deazapurine derivatives possessing the novel substitution pattern may find their application also in cell labeling in the future besides the potential use as materials in

Synthesis of 1,2-divinylcyclopropanes by metal-catalyzed cyclopropanation of 1,3-dienes with cyclopropenes as vinyl carbene precursors

• Jesús González,
• Alba de la Fuente,
• María J. González,
• Laura Díez de Tejada,
• Luis A. López and
• Rubén Vicente

Beilstein J. Org. Chem. 2019, 15, 285–290, doi:10.3762/bjoc.15.25

• in medicinal chemistry [4][5][6]. Likewise, due to its unique structure and bond properties, cyclopropanes have exclusive yet useful synthetic utilities [7], which are closely connected with the substitution pattern. For instance, the presence of vinyl groups directly attached to a cyclopropane ring

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

• ). Silanediol 9 and silyl ketene acetal 11a provide the highest yield (85%, Table 10, entry 5). The substitution pattern on the silyl ketene has a direct influence on the yield. The highest yield is reached with TMS substitution (silanediol 9, 85% yield, Table 10, entry 5; chlorosilanol 8, 54% yield, Table 10

Unexpected loss of stereoselectivity in glycosylation reactions during the synthesis of chondroitin sulfate oligosaccharides

• Teresa Mena-Barragán,
• José L. de Paz and
• Pedro M. Nieto

Beilstein J. Org. Chem. 2019, 15, 137–144, doi:10.3762/bjoc.15.14

• substitution pattern of GlcA units for the efficient synthesis of CS oligomers. Keywords: carbohydrate chemistry; chondroitin sulfate; glycosylation; oligosaccharide synthesis; stereoselectivity; Introduction Chondroitin sulfate (CS) is a highly heterogeneous polysaccharide, constituted by the repetition of

• -acylated N-TFA-protected GalNAc donors and GlcA acceptors that is not due to the presence of the fluorous tail. We hypothesized that the substitution pattern of the GlcA acceptor was responsible for the displayed stereochemistry and some experiments with model monosaccharides were planned to confirm this

Mn-mediated sequential three-component domino Knoevenagel/cyclization/Michael addition/oxidative cyclization reaction towards annulated imidazo[1,2-a]pyridines

• Olga A. Storozhenko,
• Alexey A. Festa,
• Delphine R. Bella Ndoutoume,
• Alexander V. Aksenov,
• Alexey V. Varlamov and
• Leonid G. Voskressensky

Beilstein J. Org. Chem. 2018, 14, 3078–3087, doi:10.3762/bjoc.14.287

• key intermediate of the domino sequence (Scheme 1, reaction 1). Taking into account the capability of 2-iminochromenes to perform as Michael acceptors [39][40][41], we envisioned the diversification of the substitution pattern at the chromene ring to be a realizable and an appealing target

Ring-closing-metathesis-based synthesis of annellated coumarins from 8-allylcoumarins

• Christiane Schultze and
• Bernd Schmidt

Beilstein J. Org. Chem. 2018, 14, 2991–2998, doi:10.3762/bjoc.14.278

• substitution pattern 15 was investigated starting from acrylate 12d (Scheme 2). The isomerization of the 8-allyl substituent to a prop-1-enyl substituent under the conditions used for the synthesis of precursors 10 (Table 2) stopped at 50% conversion. Higher catalyst loading and an increased reaction

Volatiles from the hypoxylaceous fungi Hypoxylon griseobrunneum and Hypoxylon macrocarpum

• Jan Rinkel,
• Alexander Babczyk,
• Tao Wang,
• Marc Stadler and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2018, 14, 2974–2990, doi:10.3762/bjoc.14.277

• derivatives. Their structures could only be unambiguously determined by comparison to all isomers with different substitution patterns. The substitution pattern of the main compound from H. griseobrunneum, the new natural product 2,4,5-trimethylanisole, was explainable by a polyketide biosynthesis mechanism

• exhibited the mass spectra shown in Figure 4E and Figure 4F that were similar to database spectra of 2,5-dimethyl-p-anisaldehyde (25) and methyl 2,5-dimethyl-p-anisate (26). The substitution pattern of these compounds is well explained by polyketide biosynthesis logic (Scheme 3). Starting from ACP-bound

• ). The chlorinated compound 2,5-dichloro-1,3-dimethoxybenzene (46) was also rigorously identified by comparison to all possible regioisomers that we had synthesised in a previous study [18]. Interestingly, the substitution pattern for the compound from H. macrocarpum is different to an isomer from the

Stereodivergent approach in the protected glycal synthesis of L-vancosamine, L-saccharosamine, L-daunosamine and L-ristosamine involving a ring-closing metathesis step

• Pierre-Antoine Nocquet,
• Aurélie Macé,
• Frédéric Legros,
• Jacques Lebreton,
• Gilles Dujardin,
• Sylvain Collet,
• Arnaud Martel,
• Bertrand Carboni and
• François Carreaux

Beilstein J. Org. Chem. 2018, 14, 2949–2955, doi:10.3762/bjoc.14.274

• Hoveyda–Grubbs second-generation (HG-II) catalyst to deliver the corresponding dihydropyrans 16 in excellent yields given that this kind of reaction can be sensitive to the substitution pattern contained in the substrate [11]. After silyl deprotection, the key C–H amination precursors 17a,b for the

Pd-Catalyzed microwave-assisted synthesis of phosphonated 13α-estrones as potential OATP2B1, 17β-HSD1 and/or STS inhibitors

• Rebeka Jójárt,
• Szabolcs Pécsy,
• György Keglevich,
• Mihály Szécsi,
• Réka Rigó,
• Csilla Özvegy-Laczka,
• Gábor Kecskeméti and
• Erzsébet Mernyák

Beilstein J. Org. Chem. 2018, 14, 2838–2845, doi:10.3762/bjoc.14.262

• 2–6, which differ in regioisomerism and/or nature of the C-3 substituent. In order to get certain functionalized 13α-estrone derivatives with a different substitution pattern for biological investigations, not only 2-bromo 1–3, but 4-bromo compounds 4–6 were also coupled with the two reagents 7a and

Assembly of fully substituted triazolochromenes via a novel multicomponent reaction or mechanochemical synthesis

• Robby Vroemans,
• Yenthel Verhaegen,
• My Tran Thi Dieu and
• Wim Dehaen

Beilstein J. Org. Chem. 2018, 14, 2689–2697, doi:10.3762/bjoc.14.246

• electron-rich triazolochromenes 5b and 5c, resulting in a drastic loss in yield for the more sterically hindered compound 5c. Furthermore, electron-deficient and halogenated analogs 5d–f were successfully synthesized. In a next series, we examined the substitution pattern on the nitroalkene part. Electron

Microwave-assisted synthesis of biologically relevant steroidal 17-exo-pyrazol-5'-ones from a norpregnene precursor by a side-chain elongation/heterocyclization sequence

• Gergő Mótyán,
• László Mérai,
• Márton Attila Kiss,
• Zsuzsanna Schelz,
• Izabella Sinka,
• István Zupkó and
• Éva Frank

Beilstein J. Org. Chem. 2018, 14, 2589–2596, doi:10.3762/bjoc.14.236

• , keto–enol tautomerism can be challenging and is of special importance in biological systems, chemical reactivity, and molecular recognition [18]. The tautomeric equilibrium in solution is strongly influenced by the substitution pattern of the heterocyclic ring, the polarity and protic nature of the

Design and synthesis of C₃-symmetric molecules bearing propellane moieties via cyclotrimerization and a ring-closing metathesis sequence

• Sambasivarao Kotha,
• Saidulu Todeti and
• Vikas R. Aswar

Beilstein J. Org. Chem. 2018, 14, 2537–2544, doi:10.3762/bjoc.14.230

• (−)-aspidophytine (5) differs from 1-acetylaspidoalbidine (4) only in the degree of unsaturation and the substitution pattern on the aromatic ring (Figure 1). The design of propellanes demands unique synthetic methods and these include: manganese or palladium-catalyzed transformations [10], the Diels–Alder (DA

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

• , and medicinal chemistry [56][57], we investigated the scope of this transformation (Scheme 3). By varying the alkene substitution pattern, we determined that the coupling of tertiary radicals is more efficient than secondary radicals. For example, methallyl p-methoxybenzoate (3a) and prenyl p

D-Fructose-based spiro-fused PHOX ligands: synthesis and application in enantioselective allylic alkylation

• Michael R. Imrich,
• Jochen Kraft,
• Cäcilia Maichle-Mössmer and
• Thomas Ziegler

Beilstein J. Org. Chem. 2018, 14, 2082–2089, doi:10.3762/bjoc.14.182

• the Ritter reaction with ether-protected carbohydrates is β as well, 10j was benzylated and 10b was obtained (Scheme 4). This proves the structure of 10b as well. The ratio of the anomers produced by the Ritter reaction depends on the substitution pattern of the pyranoside used and varies from only β

• different substitution pattern at positions 3, 4 and 5. PG: protective group, X: leaving group. Activation of 7 to oxocarbenium ion 9 in the Ritter reaction. Zemplén deacetylation of 10i. Benzylation of 10j to give 10b. Plausible mechanism of the Ritter reaction. For better clarity C-2 is not shown in

Applications of organocatalysed visible-light photoredox reactions for medicinal chemistry

• Michael K. Bogdos,
• Emmanuel Pinard and
• John A. Murphy

Beilstein J. Org. Chem. 2018, 14, 2035–2064, doi:10.3762/bjoc.14.179

• authors do not justify the selection of the particular substitution pattern with the C6 methyl and the C2 heteroatom methyl, e.g., ease of access to this type of DHPM core. Therefore, it would be interesting to see whether this method is compatible with other DHPM systems. In the same publication, the

• regioselective and follows the same substitution pattern as the electrophilic substitution of electron-rich heterocycles. Although highly elaborated structures are not presented, the mild reaction conditions and general functional group compatibility that the reaction exhibits make it well suited for LSF

Synthesis of 9-arylalkynyl- and 9-aryl-substituted benzo[b]quinolizinium derivatives by Palladium-mediated cross-coupling reactions

• Siva Sankar Murthy Bandaru,
• Darinka Dzubiel,
• Heiko Ihmels,
• Mohebodin Karbasiyoun,
• Mohamed M. A. Mahmoud and
• Carola Schulzke

Beilstein J. Org. Chem. 2018, 14, 1871–1884, doi:10.3762/bjoc.14.161

• [14][15][16][17][18] and whose interaction with the nucleic acid may be used for fluorimetric detection of the latter [19][20]. To further exploit the DNA-binding properties of this specific class of cationic hetarenes, synthetic routes to novel derivatives with the desired substitution pattern and

The phenyl vinyl ether–methanol complex: a model system for quantum chemistry benchmarking

• Dominic Bernhard,
• Fabian Dietrich,
• Mariyam Fatima,
• Cristóbal Pérez,
• Hannes C. Gottschalk,
• Axel Wuttke,
• Ricardo A. Mata,
• Martin A. Suhm,
• Melanie Schnell and
• Markus Gerhards

Beilstein J. Org. Chem. 2018, 14, 1642–1654, doi:10.3762/bjoc.14.140

• OH∙∙∙O structure was identified. In a systematic study by the Suhm group on complexes of anisole derivatives with methanol, a balance between OH∙∙∙O and OH∙∙∙π structures being very sensitive to the substitution pattern at the anisole moiety was identified [17][18]. In previous multi-spectroscopic

Direct electrochemical generation of organic carbonates by dehydrogenative coupling

• Tile Gieshoff,
• Vinh Trieu,
• Jan Heijl and
• Siegfried R. Waldvogel

Beilstein J. Org. Chem. 2018, 14, 1578–1582, doi:10.3762/bjoc.14.135

• studies on a potential scope of aromatic compounds, the symmetric 1,3,5-threefold substitution pattern showed best selectivity according to GC–MS measurements. Since the nucleophilic attack is controlled by sterics, non-symmetric substitution patterns gave weak signals and product mixtures. Generally, the

• nucleophilicity of carbonates is limited and therefore, the choice of suitable arenes is crucial. Heterofunctionalizations like fluoro, chloro, and methoxy groups are generally accepted, but it depends on the substitution pattern. The sensitive interplay of inefficient oxidation at highly positive oxidation

Recent advances in phosphorescent platinum complexes for organic light-emitting diodes

• Cristina Cebrián and
• Matteo Mauro

Beilstein J. Org. Chem. 2018, 14, 1459–1481, doi:10.3762/bjoc.14.124

• group of Chi [16] who has recently described a series of neutral platinum(II) complexes bearing isoquinolylpyrazolates, complexes 4–7 in Figure 3 [26]. Control on the intermolecular interactions was exerted through the substitution pattern, yielding solids that exhibited mechano- and solvatochromic

Hypervalent iodine-guided electrophilic substitution: para-selective substitution across aryl iodonium compounds with benzyl groups

• Cyrus Mowdawalla,
• Faiz Ahmed,
• Tian Li,
• Kiet Pham,
• Loma Dave,
• Grace Kim and
• I. F. Dempsey Hyatt

Beilstein J. Org. Chem. 2018, 14, 1039–1045, doi:10.3762/bjoc.14.91

• group. The latter of which would be consistent with the mechanism currently theorized for making alkenyl and alkynyl hypervalent iodine species [18][19][20][21][22]. While investigating the substrate scope it was found that the substitution pattern is dependent upon the substituents on the I(III

• the use of BF3·Et2O seemed to be superior to Tf2O in the case of some I(III) reactants. In all the reactions tested, there were no products formed with the ortho-substitution pattern in contrast to the RICR, however, it is clear that electron-donating groups influence the ring substitution. When

• ). These key features in the substitution pattern of the substrate scope led to experiments where tests were performed to better understand, if the HIGES reaction is a concerted mechanism, like RICR, or a stepwise process. In the article and further in a footnote of Khatri and Zhu’s publication [11

Sequential Ugi reaction/base-induced ring closing/IAAC protocol toward triazolobenzodiazepine-fused diketopiperazines and hydantoins

• Robby Vroemans,
• Fante Bamba,
• Jonas Winters,
• Joice Thomas,
• Jeroen Jacobs,
• Luc Van Meervelt,
• Jubi John and
• Wim Dehaen

Beilstein J. Org. Chem. 2018, 14, 626–633, doi:10.3762/bjoc.14.49

• , we investigated the effect of the substitution pattern on the propargylamine 2. For this, we chose easily available propargylamines 2b and 2c which gave moderate to good yields (60 and 40%, respectively) of diketopiperazine-fused triazolobenzodiazepine 7e and 7f. Furthermore, halogen substituents

Recent advances on organic blue thermally activated delayed fluorescence (TADF) emitters for organic light-emitting diodes (OLEDs)

• Thanh-Tuân Bui,
• Fabrice Goubard,
• Malika Ibrahim-Ouali,
• Didier Gigmes and
• Frédéric Dumur

Beilstein J. Org. Chem. 2018, 14, 282–308, doi:10.3762/bjoc.14.18

• substitution pattern of the carbazole unit on the photophysical properties. While maintaining the same number of carbazole units on the emitter and by varying the substitution pattern of the carbazole core, only a weak influence on the EL characteristics was evidenced [55]. In fact, performances only varied by

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

• sulfenylated dienes by dehydration. A series of aryl thiols with different steric and electronic properties give high yields of the thiol–yne products. Noteworthy is the high E-selectivity of the resulting alkene. Dependent on the substitution pattern of the aryl thiol a ratio up to 60:1 was observed due to

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation and chlorination. Part 2: Use of CF₃SO₂Cl

• Hélène Chachignon,
• Hélène Guyon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2800–2818, doi:10.3762/bjoc.13.273

• also suitable to carry out this reaction [12]. The same tendencies in term of reactivity of the substrates depending on their substitution pattern was observed, and similar yields were achieved (Scheme 10). Similarly, Ir(ppy)2(dtbbpy)PF6 was also described as an appropriate catalyst for this cascade

• selectively place from a direction anti to the CF3 group, probably because of electrostatic repulsion. The reaction proceeded smoothly with prop-1-yn-1-ylbenzene derivatives, indifferently to the substitution pattern of the aryl moiety. As for the R group, alkyl, ester or amide moieties were well-tolerated