Machine learning-guided strategies for reaction conditions design and optimization

• Lung-Yi Chen and
• Yi-Pei Li

Beilstein J. Org. Chem. 2024, 20, 2476–2492, doi:10.3762/bjoc.20.212

• and local models to guide the design of synthetic processes. Global models exploit the information from comprehensive databases to suggest general reaction conditions for new reactions, while local models fine-tune the specific parameters for a given reaction family to improve yield and selectivity

• volumes of data and accelerate the prediction of optimal reaction condition combinations. It has been widely demonstrated that ML algorithms can be used for various chemistry-related tasks, such as yield prediction [14][15], site-selectivity prediction [16][17], reaction conditions recommendation [18

• ][116][117], regioselectivity, and site-selectivity [16][17][118][119][120]. However, this approach is also computationally demanding and requires a good initial guess of the TS structure. Moreover, it may face difficulties in simulating some classes of reactions and large-size molecules [121], and the

Homogeneous continuous flow nitration of O-methylisouronium sulfate and its optimization by kinetic modeling

• Jiapeng Guo,
• Weike Su and
• An Su

Beilstein J. Org. Chem. 2024, 20, 2408–2420, doi:10.3762/bjoc.20.205

• ]. The reaction time and temperature were reduced from >2 h and 80 °C in industrial operation to 10 min and 65 °C in the microreactor with high conversion and selectivity. Since O-methylisouronium sulfate can be dissolved in high concentrations of sulfuric acid, it is expected to construct a homogeneous

Asymmetric organocatalytic synthesis of chiral homoallylic amines

• Nikolay S. Kondratyev and
• Andrei V. Malkov

Beilstein J. Org. Chem. 2024, 20, 2349–2377, doi:10.3762/bjoc.20.201

• simultaneous construction of homoallylamine scaffolds, exemplified by compounds 16–20 with up to 3 contiguous stereocentres, including a quaternary centre in moderate to high yields (60–94%) with 90–99% ee and dr in the range from 97:3 to >99:1 (Scheme 4). The selectivity of the reaction arises from the

• 24, which supported the hypotheses regarding the selectivity-determining transition states arrangement. It is important to note, that boronic acids 14 are highly sensitive to oxidation by air and could only be purified in air-free conditions and stored in airtight containers. Additionally

• give the desired product 99 after 72 h returning hemiaminal (Scheme 21). Alkyl acetals, such as cyclohexyl carboxaldehyde acetal reacted sluggishly with low yield and selectivity (<10% yield, 43–50% ee), possibly due to their inability to participate in π–π interactions. In general, the π-stacking

Stereoselective mechanochemical synthesis of thiomalonate Michael adducts via iminium catalysis by chiral primary amines

• Michał Błauciak,
• Dominika Andrzejczyk,
• Błażej Dziuk and
• Rafał Kowalczyk

Beilstein J. Org. Chem. 2024, 20, 2313–2322, doi:10.3762/bjoc.20.198

• -based catalytic system for the highly stereoselective addition of various bisthiomalonates to chalcones and dienones [29]. While recognizing the potential for greater selectivity enhancement and time savings with ball milling, hydrogen-bonding catalysis was effective only with aromatic enones, yielding

• planetary mill. Further variations of system A concerned the acid’s role. However, no impact of the acid was noted while using the amino acid derivative AC-2, but the dramatic loss of selectivity was observed in the case of chiral phosphoric acid’s application AC-3. Thus, it is rather unlikely the iminium

Catalysing (organo-)catalysis: Trends in the application of machine learning to enantioselective organocatalysis

• Stefan P. Schmid,
• Leon Schlosser,
• Frank Glorius and
• Kjell Jorner

Beilstein J. Org. Chem. 2024, 20, 2280–2304, doi:10.3762/bjoc.20.196

• decades have showed an increased interest from the community. This review gives an overview of the work in the field of ML in organocatalysis. The review starts by giving a short primer on ML for experimental chemists, before discussing its application for predicting the selectivity of organocatalytic

• . Keywords: catalyst design; machine learning; modelling; organocatalysis; selectivity prediction; Introduction Since the beginning of the 21st century, organocatalysts [1] have established themselves as a third group of homogeneous catalysts, next to biocatalysts [2] (enzymes) and transition metal-based

• energies of relevant species either via force field or quantum chemical methods to assess the properties of a reaction such as activation energies or selectivity. Irrespective of the degree of automation, in silico calculations are often less time-sensitive than wet-lab experiments and can be used to

Selective hydrolysis of α-oxo ketene N,S-acetals in water: switchable aqueous synthesis of β-keto thioesters and β-keto amides

• Haifeng Yu,
• Wanting Zhang,
• Xuejing Cui,
• Zida Liu,
• Xifu Zhang and
• Xiaobo Zhao

Beilstein J. Org. Chem. 2024, 20, 2225–2233, doi:10.3762/bjoc.20.190

• thioesters and β-keto amides by simply changing reaction conditions. These features, including a good substrate scope, excellent yield and selectivity and ease of scale-up, rendered the green hydrolysis reaction very environment-friendly, practical, and attractive. Experimental 1H and 13C{1H} NMR spectra

O,S,Se-containing Biginelli products based on cyclic β-ketosulfone and their postfunctionalization

• Kateryna V. Dil and
• Vitalii A. Palchykov

Beilstein J. Org. Chem. 2024, 20, 2143–2151, doi:10.3762/bjoc.20.184

• acidic conditions since such conditions enhance the selectivity, so various catalysts, mainly acidic, were tested for the model Biginelli reaction and the results are shown in Table 1. One of the most effective promoters for this type of reaction is TMSCl [29][30][31] and we also tried to involve TMSCl

• (Table 1, entry 7). Reflux in alcoholic media in the presence of p-toluenesulfonic acid or CAN (ceric ammonium nitrate) was also not particularly successful (Table 1, entries 8 and 9, yield 32–35%). We subsequently explored a range of reaction conditions to improve overall yield and selectivity. We

Factors influencing the performance of organocatalysts immobilised on solid supports: A review

• Zsuzsanna Fehér,
• Dóra Richter,
• Gyula Dargó and
• József Kupai

Beilstein J. Org. Chem. 2024, 20, 2129–2142, doi:10.3762/bjoc.20.183

• , including the type of support, immobilisation techniques and the resulting interactions. In addition, the influence of these factors on catalytic activity, selectivity and recyclability is discussed, providing an insight into optimising the performance of immobilised organocatalysts for practical

• reaction components and the catalyst are in the same phase. Active catalytic sites are readily accessible to the reactants and therefore generally result in higher catalytic activity and selectivity [8]. As a result, homogeneous catalysis is generally preferred to heterogeneous catalysis, especially in the

• influence on the properties and thus performance of the resulting heterogeneous catalyst. However, immobilisation and structural modification introduce additional steps in the synthesis of the catalyst. Moreover, the catalytic activity and selectivity of immobilised catalysts are often lower than those of

From perfluoroalkyl aryl sulfoxides to ortho thioethers

• Yang Li,
• Guillaume Dagousset,
• Emmanuel Magnier and
• Bruce Pégot

Beilstein J. Org. Chem. 2024, 20, 2108–2113, doi:10.3762/bjoc.20.181

• their ability to be engaged in such a rearrangement [4][5]. Upon activation with trifluoromethanesulfonic anhydride and under heating, we showed their transformation to ortho thioethers with a fairly acceptable selectivity towards the pathway of sulfilimine synthesis (Scheme 1b). Following our seminal

• arenes in good yield. Inspired and stimulated by this abundant literature, and as part of our research program focused on creating novel perfluoroalkylsulfur derivatives, we became interested in a reappraisal of our previous study with the aim of increasing its scope as well as the yield and selectivity

Computational toolbox for the analysis of protein–glycan interactions

• Ferran Nieto-Fabregat,
• Maria Pia Lenza,
• Angela Marseglia,
• Cristina Di Carluccio,
• Antonio Molinaro,
• Alba Silipo and
• Roberta Marchetti

Beilstein J. Org. Chem. 2024, 20, 2084–2107, doi:10.3762/bjoc.20.180

Multicomponent syntheses of pyrazoles via (3 + 2)-cyclocondensation and (3 + 2)-cycloaddition key steps

• Ignaz Betcke,
• Alissa C. Götzinger,
• Maryna M. Kornet and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2024, 20, 2024–2077, doi:10.3762/bjoc.20.178

• phosphane ligands is crucial for the selectivity in this reaction. Suzuki coupling can also serve for the functionalization of iodochromones 55, which, as α,β-unsaturated ketones, undergo ring opening under the reaction conditions, followed by Michael addition–cyclocondensation. Xie et al. devised a method

Harnessing the versatility of hydrazones through electrosynthetic oxidative transformations

• Aurélie Claraz

Beilstein J. Org. Chem. 2024, 20, 1988–2004, doi:10.3762/bjoc.20.175

• reaction conditions to selectively oxidize the desired compound. In some cases, the use of an electromediatior such as an iodide anion helped in achieving the desired selectivity. In line with the continuing increasing interest for both electrosynthetic organic transformations and the chemistry of

Radical reactivity of antiaromatic Ni(II) norcorroles with azo radical initiators

• Siham Asyiqin Shafie,
• Ryo Nozawa,
• Hideaki Takano and
• Hiroshi Shinokubo

Beilstein J. Org. Chem. 2024, 20, 1967–1972, doi:10.3762/bjoc.20.172

• presented. We also discuss the selectivity of the radical addition to Ni(II) norcorroles using DFT calculations. Results and Discussion Reactivity with azo radical initiators We selected 2,2'-azobis(isobutyronitrile) (AIBN) as a radical source. Ni(II) dimesitylnorcorrole 1 was treated with AIBN in refluxing

Regioselective alkylation of a versatile indazole: Electrophile scope and mechanistic insights from density functional theory calculations

• Pengcheng Lu,
• Luis Juarez,
• Paul A. Wiget,
• Weihe Zhang,
• Krishnan Raman and
• Pravin L. Kotian

Beilstein J. Org. Chem. 2024, 20, 1940–1954, doi:10.3762/bjoc.20.170

• employed as nucleophiles in chemical transformations, and a mixture of both N1- and N2-alkylated products is formed, depending on the reaction conditions, with little selectivity in regards to substituent effects [27][28][29][30][31][32][33]. Considering the importance of indazoles as a widely used

• for N1/N2 discrimination studies. The existing approaches for generating N-substituted indazoles of compound 6 often lead to a mixture of N1- and N2-alkylated indazoles with either low selectivity or moderate yields depending on the conditions used. For example, Takahashi et al. obtained N1- and N2

• -substituted indazole analogs in 44% and 40% yields, respectively, by treating compound 6 with methyl iodide and potassium carbonate in dimethylformamide (DMF) at room temperature for 17 h [40]. Other works have shown poor selectivity when 6 and other isomers similar to 6 were reacted with isopropyl iodide and

A new platform for the synthesis of diketopyrrolopyrrole derivatives via nucleophilic aromatic substitution reactions

• Vitor A. S. Almodovar and
• Augusto C. Tomé

Beilstein J. Org. Chem. 2024, 20, 1933–1939, doi:10.3762/bjoc.20.169

• synthesis of highly fluorescent DPP derivatives through straightforward nucleophilic aromatic substitution reactions with thiols and phenols. These nucleophilic substitutions occur at room temperature and manifest a remarkable selectivity for the 4-position of the pentafluorophenyl groups. Both symmetrical

Negishi-coupling-enabled synthesis of α-heteroaryl-α-amino acid building blocks for DNA-encoded chemical library applications

• Matteo Gasparetto,
• Balázs Fődi and
• Gellért Sipos

Beilstein J. Org. Chem. 2024, 20, 1922–1932, doi:10.3762/bjoc.20.168

• ][28]. However, the selectivity of these photoredox reactions is driven by the structural properties of the heteroaromatic ring. During the preparation of this article, the Meggers group published an outstanding enantioselective iron-catalyzed α-amination pathway (Scheme 1b) [29]. The method is widely

Novel oxidative routes to N-arylpyridoindazolium salts

• Oleg A. Levitskiy,
• Yuri K. Grishin and
• Tatiana V. Magdesieva

Beilstein J. Org. Chem. 2024, 20, 1906–1913, doi:10.3762/bjoc.20.166

• [13][14][15][16][17][18][19], N,N-diarylbenzidines [20][21], N,N-diaryldihydrophenazines [20][21] and some others. Therefore, the selectivity issue is of primary importance. The guidelines for prediction of the dominant reaction path in the competing oxidative transformations of variously substituted

2-Heteroarylethylamines in medicinal chemistry: a review of 2-phenethylamine satellite chemical space

• Carlos Nieto,
• Alejandro Manchado,
• Ángel García-González,
• David Díez and
• Narciso M. Garrido

Beilstein J. Org. Chem. 2024, 20, 1880–1893, doi:10.3762/bjoc.20.163

• importance in medicinal chemistry, as it can be employed as a rational to expand bioactive chemical space to tackle lead optimization issues like lack of potency, efficacy, and selectivity or pharmacokinetic/dynamic issues. One of the most important building blocks (in the sense of participating in a vast

• comparable to the original [1]. The main purpose of this approach is quality improvement, such as activity, selectivity, bioavailability, metabolism, and/or toxicity, while expanding the chemical space surrounding bioactive compounds [2][3]. Benzene-to-heteroaromatic ring replacement represents a classical

• )-2, also called lanicemine, AZD6765 or AR-R15896AR, was described as a competitive ketamine alternative without psychotomimetic side effects, although potency and selectivity were significantly lower (Scheme 2) [8][9]. Dukat et al. [10] developed flexible 3-(2-aminoethyl)pyridine (AEP) analogs 3–5 as

The Groebke–Blackburn–Bienaymé reaction in its maturity: innovation and improvements since its 21st birthday (2019–2023)

• Cristina Martini,
• Muhammad Idham Darussalam Mardjan and
• Andrea Basso

Beilstein J. Org. Chem. 2024, 20, 1839–1879, doi:10.3762/bjoc.20.162

Synthesis of polycyclic aromatic quinones by continuous flow electrochemical oxidation: anodic methoxylation of polycyclic aromatic phenols (PAPs)

• Hiwot M. Tiruye,
• Solon Economopoulos and
• Kåre B. Jørgensen

Beilstein J. Org. Chem. 2024, 20, 1746–1757, doi:10.3762/bjoc.20.153

• structure B, which is further destabilized by the neighbouring ketone. A similar resonance hybrid will be formed for molecules substituted in the 4-position, like 6b, explaining the selectivity towards p-quinones. Abstraction of a proton rearomatizes the molecule before another cation is formed in the

Syntheses and medicinal chemistry of spiro heterocyclic steroids

• Laura L. Romero-Hernández,
• Ana Isabel Ahuja-Casarín,
• Penélope Merino-Montiel,
• Sara Montiel-Smith,
• José Luis Vega-Báez and
• Jesús Sandoval-Ramírez

Beilstein J. Org. Chem. 2024, 20, 1713–1745, doi:10.3762/bjoc.20.152

• perspective, the incorporation of a spiro fragment significantly impacts the properties of the drug candidate. Introducing a spirocyclic moiety often leads to increased potency and selectivity, as observed in comparisons between spirocycles and their non-spiro counterparts. Furthermore, several examples

• , albeit less potent than the reference drug. However, many oxazolines showed improved selectivity, with greater separation of antiprogestational and antiglucocorticoid activity (Scheme 19) [38]. 1,2-Aminoalcohols have been extensively utilized as building blocks for synthesizing spiro-1,3-oxazolidin-2

Chemo-enzymatic total synthesis: current approaches toward the integration of chemical and enzymatic transformations

• Ryo Tanifuji and
• Hiroki Oguri

Beilstein J. Org. Chem. 2024, 20, 1693–1712, doi:10.3762/bjoc.20.151

• the Diels–Alder reactions (Scheme 6B). Notably, MaDA-3 exhibited high exo-selectivity (original MaDA: endo-selective) and enabled the enantioselective rapid total synthesis of guangsangon J (60) and mongolicin F (61), which are epimers of 58 and 3, respectively. Comparative analysis of the X-ray

• approach, they used a chiral boron catalyst as a Lewis acid and achieved at best an endo/exo selectivity of 1.9:1 in a similar DA reaction. The use of Diels–Alderase in their recent work significantly improved the endo/exo selectivity under mild conditions in water, thereby highlighting the strengths of

• -stage enzymatic functionalization of core scaffolds could be effective. Selectivity towards target biomolecules can be tailored by gradually increasing the oxidation level of the complex scaffold or by further site- and stereoselective modifications. Through rational enzyme engineering, the selectivity

Methyltransferases from RiPP pathways: shaping the landscape of natural product chemistry

• Maria-Paula Schröder,
• Isabel P.-M. Pfeiffer and
• Silja Mordhorst

Beilstein J. Org. Chem. 2024, 20, 1652–1670, doi:10.3762/bjoc.20.147

• single methyl group has the ability to modulate a drug’s efficacy by orders of magnitude; this occurrence is also called the ‘magic methyl effect’ [14][15]. Compared to chemical methylation reactions, a biocatalytic methylation often offers several advantages. MTs exhibit high selectivity and are

• bonds and primary amines of the amino acid chains are available for methylation, leading to poor site selectivity of any methylating reaction [39]. Therefore, either pre-methylated amino acids or short methylated peptides are incorporated into the full-length peptide. Direct O-methylation of an O

• both methylated and unmethylated versions of the same amino acid, simply supplying both tRNAs is not sufficient, as the ribosome has a higher selectivity for the tRNA charged with the natural amino acid. This can be addressed by synthesising tRNA for a stop codon charged with the desired modified amino

Benzylic C(sp³)–H fluorination

• Alexander P. Atkins,
• Alice C. Dean and
• Alastair J. J. Lennox

Beilstein J. Org. Chem. 2024, 20, 1527–1547, doi:10.3762/bjoc.20.137

• incorporate fluorine into compounds of interest, with regio and site selectivity pre-determined by the nature of the functionalised carbon. However, the development of C(sp3)–H fluorination methods represents a more sustainable and versatile approach, as there is no requirement to pre-functionalise the

• bond formation to afford the acyloxylation product was observed, and favoured when using directing groups with less steric bulk. This product had the opposite stereochemistry to the fluorination product suggesting it occurred via a competitive SN2 pathway. This is supported by the selectivity for C–O

• on the arene were unsuccessful. Without substituents on the ring, aryl C–H activation and subsequent C–O bond formation occurred along with benzylic fluorination (7) (low efficiency). The presence of a p-methoxy group resulted in a switch in selectivity to acyloxylation 8’ as the major product. The

Towards an asymmetric β-selective addition of azlactones to allenoates

• Behzad Nasiri,
• Ghaffar Pasdar,
• Paul Zebrowski,
• Katharina Röser,
• David Naderer and
• Mario Waser

Beilstein J. Org. Chem. 2024, 20, 1504–1509, doi:10.3762/bjoc.20.134

• (Table 1, entry 7, similar non-selective results were obtained when using THF), were found to be less-suited however. Testing the 3,4,5-trifluorobenzene-decorated catalyst B2 with K2CO3 in toluene next (Table 1, entry 8) allowed for a slightly higher selectivity but still gave only a relatively low yield