α-Ketol and α-iminol rearrangements in synthetic organic and biosynthetic reactions

• Scott Benz and
• Andrew S. Murkin

Beilstein J. Org. Chem. 2021, 17, 2570–2584, doi:10.3762/bjoc.17.172

• % yield), para-alkoxy and para-halogen substituents (45–69%), ortho-methyl (74%), and meta-methyl (80% as a 65:35 mixture of regioisomers). Electron-withdrawing groups (nitro, cyano, and methyl ester) stopped at the ketone intermediate. Interestingly, another tandem sequence that exploits the relief of

Synthesis of new substituted 7,12-dihydro-6,12-methanodibenzo[c,f]azocine-5-carboxylic acids containing a tetracyclic tetrahydroisoquinoline core structure

• Agnieszka Grajewska,
• Maria Chrzanowska and
• Wiktoria Adamska

Beilstein J. Org. Chem. 2021, 17, 2511–2519, doi:10.3762/bjoc.17.168

• without alkoxy substituents, prepared from phenylboronic acid (5d), glyoxylic acid hydrate (4) and an N-benzyl aminoacetal 3d with good yield 79% (Scheme 4), it was necessary to perform the cyclization reaction using 70% HClO4 instead of 20% HCl. In these conditions, the desired product 7f was obtained

Facile and innovative catalytic protocol for intramolecular Friedel–Crafts cyclization of Morita–Baylis–Hillman adducts: Synergistic combination of chiral (salen)chromium(III)/BF₃·OEt₂ catalysis

• Karthikeyan Soundararajan,
• Helen Ratna Monica Jeyarajan,
• Raju Subimol Kamarajapurathu and
• Karthik Krishna Kumar Ayyanoth

Beilstein J. Org. Chem. 2021, 17, 2186–2193, doi:10.3762/bjoc.17.140

• Basavaiah et al. [10] on the phosphorous pentoxide-catalysed synthesis of indene using alkoxy-substituted MBH adducts. Later Shanmugam et al. [11] reported a Mont. K10-catalysed synthesis of indenes from similar alkoxy MBH adducts. Thereafter Lee et al. [12] and Xu et al. [13] synthesised indenes in

Preparation of mono-substituted malonic acid half oxyesters (SMAHOs)

• Tania Xavier,
• Sylvie Condon,
• Christophe Pichon,
• Erwan Le Gall and
• Marc Presset

Beilstein J. Org. Chem. 2021, 17, 2085–2094, doi:10.3762/bjoc.17.135

• ][38]. Despite its efficiency, this strategy remains limited regarding the nature of the alkoxy group of the ester function (generally Me or Et), as it arises from the parent malonate. In order to introduce diversity at this position, the privileged route is based on the opening of a Meldrum's acid

Recent advances in the syntheses of anthracene derivatives

• Giovanni S. Baviera and
• Paulo M. Donate

Beilstein J. Org. Chem. 2021, 17, 2028–2050, doi:10.3762/bjoc.17.131

• intramolecular Friedel–Crafts-type cyclization. This was the first report of the same molecule bearing an acid-sensitive acetal and dibenzyl alkoxy groups. The key steps described in the work were protection of the aldehyde group of 6-bromopiperonal (80) by using 1,2-ethanediol or 1,3-propanediol, followed by

• corresponding [n+2]acene-2,3-diethyl diesters 95 by the procedure described above. The scope of the reaction included five examples of substituted anthracene-2,3-dicarboxylates bearing Cl or alkoxy groups (43–86% yield). Lin et al. also applied the same approach to synthesize acene-2,3-dinitriles 96 by using

• step, a platinum-catalyzed intramolecular cycloaromatization of 119 provided dibenzo[a,h]anthracenes 120 bearing methyl and alkoxy groups in low to moderate yields (26–51%) [61]. Metal-catalyzed intramolecular double-cyclization In 2012, Nishiyama’s research group synthesized dibenzo[a,h]anthracenes by

On the application of 3d metals for C–H activation toward bioactive compounds: The key step for the synthesis of silver bullets

• Renato L. Carvalho,
• Amanda S. de Miranda,
• Mateus P. Nunes,
• Roberto S. Gomes,
• Guilherme A. M. Jardim and
• Eufrânio N. da Silva Júnior

Beilstein J. Org. Chem. 2021, 17, 1849–1938, doi:10.3762/bjoc.17.126

Co-crystallization of an organic solid and a tetraaryladamantane at room temperature

• Fabian Rami,
• Jan Nowak,
• Felix Krupp,
• Wolfgang Frey and
• Clemens Richert

Beilstein J. Org. Chem. 2021, 17, 1476–1480, doi:10.3762/bjoc.17.103

• group. But again, hydrogen bonds between phenol hydroxy groups and the alkoxy substituent of the crystallization chaperone can be resolved. So, in both co-crystal lattices, hydrogen bonding stabilizes the packing arrangement. For TDA/phenol, the host builds the crystal lattice with TDA molecules in

N-tert-Butanesulfinyl imines in the asymmetric synthesis of nitrogen-containing heterocycles

• Joseane A. Mendes,
• Paulo R. R. Costa,
• Miguel Yus,
• Francisco Foubelo and
• Camilla D. Buarque

Beilstein J. Org. Chem. 2021, 17, 1096–1140, doi:10.3762/bjoc.17.86

• -tert-butanesulfinyl α-alkoxy aldimines 126 [124]. In this one-pot approach, a successive nucleophilic addition–cyclization–desulfinylation took place, leading directly to piperidinones 127. The reactions were performed in THF at −78 °C for 3 hours. Yields ranged from moderate to excellent with

• , and regulation of the immune response. Starting from α-alkoxy aldimines ent-126, the utility of this methodology was also demonstrated in the synthesis of alkaloid (+)-cassine (130), isolated from the leaves and twigs of Cassia excelsa, displaying antimicrobial activity. Methylmagnesium bromide was

Synthetic accesses to biguanide compounds

• Oleksandr Grytsai,
• Cyril Ronco and
• Rachid Benhida

Beilstein J. Org. Chem. 2021, 17, 1001–1040, doi:10.3762/bjoc.17.82

Beyond ribose and phosphate: Selected nucleic acid modifications for structure–function investigations and therapeutic applications

• Christopher Liczner,
• Kieran Duke,
• Gabrielle Juneau,
• Martin Egli and
• Christopher J. Wilds

Beilstein J. Org. Chem. 2021, 17, 908–931, doi:10.3762/bjoc.17.76

• mixture of triethylammonium bicarbonate (TEAB) and N,N-dimethylformamide (DMF) followed by a sodium borohydride reduction to give the 4'-alkoxy products [202]. The 4'-methoxy-2'-deoxynucleosides exhibited high resistance towards depurination under acidic conditions [202]. In contrast, nucleosides that are

Synthetic reactions driven by electron-donor–acceptor (EDA) complexes

• Zhonglie Yang,
• Yutong Liu,
• Kun Cao,
• Xiaobin Zhang,
• Hezhong Jiang and
• Jiahong Li

Beilstein J. Org. Chem. 2021, 17, 771–799, doi:10.3762/bjoc.17.67

• electron-withdrawing groups, the scope of the reaction comprises anilines including electron-withdrawing or electron-donating substituents in the arene, except N-acetylated or ortho-halogenated anilines. In 2017, Chen and colleagues [21] reported a method that promoted the formation of an alkoxy radical

• through an EDA complex under visible-light irradiation. The EDA complex formed by electron donor Hantzsch ester (HE) 79 and electron acceptor N-acyloxybenzamide 78 was produced by light-promoted SET, providing alkoxy radicals that could give carbon radicals by removing one molecule of acetaldehyde (Scheme

•  27). It is worth noting that EDA complex has been firstly employed for the generation of alkoxy radicals under visible-light irradiation, achieving selective C(sp3)–C(sp3)-bond cleavage and allylation or alkenylation. In 2017, Li and colleagues [57] reported a reaction for the synthesis of

Synthetic strategies of phosphonodepsipeptides

• Jiaxi Xu

Beilstein J. Org. Chem. 2021, 17, 461–484, doi:10.3762/bjoc.17.41

• library of carboxylic acids 72 in the presence of coupling reagents (Scheme 11) [27]. Alternatively, the 1,3-protected glycerol 73 was first converted into various 2,3-protected glycerols 74, which were further transformed to methyl 2-alkoxy-3-hydroxypropanoates 75. Following a similar strategy as above

Tuning the solid-state emission of liquid crystalline nitro-cyanostilbene by halogen bonding

• Subrata Nath,
• Alexander Kappelt,
• Matthias Spengler,
• Bibhisan Roy,
• Jens Voskuhl and
• Michael Giese

Beilstein J. Org. Chem. 2021, 17, 124–131, doi:10.3762/bjoc.17.13

• and S15). In our initial set of assemblies, we combined F4St with NO2-Cn with varying alkoxy-chain lengths (n = 8, 9, 10 and 11). The halogen-bonded assemblies exhibited mesogenic behaviour starting with an alkoxy chain length of n = 8. POM investigations revealed nematic mesophases for all complexes

• (see also Figure 2b) which is in contrast to the behaviour of pristine NO2-Cn showing a smectic phase for the alkoxy chain lengths of n = 10 or 11. A strong odd–even effect was observed for the NO2-Cn∙∙∙F4St assemblies which indicates a significant impact of the alkyl chain length on the packing of the

• alkoxy chain on the halogen bond accepting moiety (NO2-C9 and NO2-C11) displayed an enantiotropic phase behaviour. For the NO2-Cn∙∙∙F4Az assemblies no significant effect of the alkoxy chain length on the transition temperatures was observed. The temperature ranges of the nematic phases are significantly

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

• forms is proposed to involve the alkoxy group rather than the N–H bond that is usually invoked. Then, upon photoexcitation, Dexter energy transfer to the maleimide is dominant to generate 3maleimide rather than energy transfer to the quinolone. While some maleimide dimerisation is observed, which

Synthesis of 1,4-benzothiazinones from acylpyruvic acids or furan-2,3-diones and o-aminothiophenol

• Ekaterina E. Stepanova,
• Maksim V. Dmitriev and
• Andrey N. Maslivets

Beilstein J. Org. Chem. 2020, 16, 2322–2331, doi:10.3762/bjoc.16.193

• -diones V, and acetylenedicarboxylates VI with o-aminophenols or o-phenylenediamines (Scheme 3) [1][2][3][4][5][6]. Since the approach to alkoxy-substituted BTAs III (Figure 1, R = OAlk) has already been reported (Scheme 2) [21], we focused our research on aryl/alkyl-substituted BTAs III (Figure 1, R = Ar

Chan–Evans–Lam N1-(het)arylation and N1-alkеnylation of 4-fluoroalkylpyrimidin-2(1H)-ones

• Viktor M. Tkachuk,
• Oleh O. Lukianov,
• Mykhailo V. Vovk,
• Isabelle Gillaizeau and
• Volodymyr A. Sukach

Beilstein J. Org. Chem. 2020, 16, 2304–2313, doi:10.3762/bjoc.16.191

• substituents (a methoxy or 1-pyrrolidinyl group) at position 4 of 3-pyridylboronic acid enabled increased yields of the target products 3s and 3t thus opening a preparative pathway to a wide variety of 4-alkoxy-3-pyridyl and 4-dialkylamino-3-pyridyl derivatives. Hetarylboronic acids containing a more electron

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

Rearrangement of o-(pivaloylaminomethyl)benzaldehydes: an experimental and computational study

• Csilla Hargitai,
• Györgyi Koványi-Lax,
• Tamás Nagy,
• Péter Ábrányi-Balogh,
• András Dancsó,
• Gábor Tóth,
• Judit Halász,
• Angéla Pandur,
• Gyula Simig and
• Balázs Volk

Beilstein J. Org. Chem. 2020, 16, 1636–1648, doi:10.3762/bjoc.16.136

• Centre for Natural Sciences, P.O. Box 286, H-1519 Budapest, Hungary Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, Szent Gellért tér 4, H-1111 Budapest, Hungary 10.3762/bjoc.16.136 Abstract Treatment of alkoxy-substituted o-(pivaloylaminomethyl

• DCM reaction medium. This is further supported by the recent results of Allen et al., who have shown that CHCl3 and DCM molecules exhibited the same interactions also in crystal packing [33]. Conclusion When alkoxy-substituted o-(pivaloylaminomethyl)benzaldehydes 1a,b were kept in solution (DCM or THF

Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

An overview on disulfide-catalyzed and -cocatalyzed photoreactions

• Yeersen Patehebieke

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

• , cyclopentanone, and three carbon ring-expanded 1,3-diones from vinyl spiro epoxides [14]. The reaction is initiated by the addition of a thiyl radical to the vinyl epoxide 24, followed by the epoxide fragmentation to the alkoxy radical 25. Then, the β-cleavage to form the carbon-centered radical 26, the final

Recent synthesis of thietanes

• Jiaxi Xu

Beilstein J. Org. Chem. 2020, 16, 1357–1410, doi:10.3762/bjoc.16.116

• (trifluoromethyl)-1,3-dithietane (363) with alkyl vinyl ethers 371 or phenyl vinyl sulfide (372b) in DMSO at 70 °C afforded the corresponding 2,2-bis(trifluoromethyl)-3-alkoxy/phenylthiothietanes 374 and 375b, respectively, with 1,3-dithiolanes 382 as byproducts [101] (Scheme 78). The reactions of 2,2,4,4-tetrakis

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

• . The formed N-alkoxylated intermediate is converted into the desired product 39.2 after oxidation and releases another alkoxy radical at the same time. The measured quantum yield (Φ = 4.4) indicates that a chain mechanism is operative. Recently, the same group applied a similar organophotocatalytic

• used as initators for the synthesis of highly functionalized benzo[b]phosphole oxides from arylphosphine oxide and alkynes [162]. Alkyl hydroperoxides can act as oxidants in photocatalytic cycles, furnishing the desired alkoxy radicals. Several organic dyes have been exploited in these processes

Efficient synthesis of piperazinyl amides of 18β-glycyrrhetinic acid

• Dong Cai,
• ZhiHua Zhang,
• Yufan Meng,
• KaiLi Zhu,
• LiYi Chen,
• ChangXiang Yu,
• ChangWei Yu,
• ZiYi Fu,
• DianShen Yang and
• YiXia Gong

Beilstein J. Org. Chem. 2020, 16, 798–808, doi:10.3762/bjoc.16.73

• instance, the hydroxy group can be converted into an oxime, acyloxyimino, alkoxyimino, alkoxy and 3-oxo group [9]. As a proteasome inhibitor, compound a suppresses the chymotrypsin-like activity of the proteasome in MT4 cells with an IC50 of 0.22 μM, nearly 100-fold more potent than 18β-glycyrrhetinic acid

Synthesis of C₇₀-fragment buckybowls bearing alkoxy substituents

• Yumi Yakiyama,
• Shota Hishikawa and
• Hidehiro Sakurai

Beilstein J. Org. Chem. 2020, 16, 681–690, doi:10.3762/bjoc.16.66

• Yumi Yakiyama Shota Hishikawa Hidehiro Sakurai Division of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan 10.3762/bjoc.16.66 Abstract Buckybowls bearing a C70 fragment having two alkoxy groups were synthesized and their structural

• the external aromatic ring of the indenopyrene using various types of o-bromo arylaldehydes. Related to our study on buckybowl-containing liquid crystals [19], we planned to introduce alkoxy groups on the 1 framework. Here, we report the synthesis and characterization of dimethoxy derivative 5a and

• succeeded in synthesizing three different alkoxy-substituted C70-fragment buckybowls 5a–c. In particular, 5c was not an intended molecule, but was formed unexpectedly through the rearrangement through the Pd-catalyzed C–H bond activation reaction. The X-ray crystal structure analysis of 5a–c clearly

Cascade trifluoromethylthiolation and cyclization of N-[(3-aryl)propioloyl]indoles

• Ming-Xi Bi,
• Shuai Liu,
• Yangen Huang,
• Xiu-Hua Xu and
• Feng-Ling Qing

Beilstein J. Org. Chem. 2020, 16, 657–662, doi:10.3762/bjoc.16.62

• effect of the substitution on the indole ring. Both electron-donating and withdrawing groups at different positions of the indole ring produced the bis(trifluoromethylthiolated) products 2a–o in moderate to good yields. A wide range of functionalities such as alkyl, alkoxy, nitro, nitrile, ester