Oxa-Michael-initiated cascade reactions of levoglucosenone

• Julian Klepp,
• Thomas Bousfield,
• Hugh Cummins,
• Sarah V. A.-M. Legendre,
• Jason E. Camp and
• Ben W. Greatrex

Beilstein J. Org. Chem. 2022, 18, 1457–1462, doi:10.3762/bjoc.18.151

• elimination of methanol rather than exocyclic elimination of water, and regioisomeric Rauhut–Currier reaction. Compound 7 was found to be unstable after isolation, possibly due to intermolecular reactions of the electron-poor olefin and furan ring. When a slight excess of 1 was used, only 6n was isolated

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

• comparable to the stoichiometric reactivity of boranes [32]. Nitriles containing heterocycles underwent hydroboration in moderate yield (52–58%), with furan and thiophene groups tolerated (1v, 1w). Furan-2-ylmethanamine hydrochloride 1v can be converted into furosemide, a diuretic on the WHO list of

Cytochrome P450 monooxygenase-mediated tailoring of triterpenoids and steroids in plants

• Karan Malhotra and
• Jakob Franke

Beilstein J. Org. Chem. 2022, 18, 1289–1310, doi:10.3762/bjoc.18.135

• formation in the product melianol (21). It is believed that these transformations are the starting point for formation of the characteristic furan ring of limonoids [29]. Taken together, these case studies not only represent impressive examples how CYPs create chemical complexity in plant triterpenoid and

Modular synthesis of 2-furyl carbinols from 3-benzyldimethylsilylfurfural platforms relying on oxygen-assisted C–Si bond functionalization

• Sebastien Curpanen,
• Per Reichert,
• Gabriele Lupidi,
• Giovanni Poli,
• Julie Oble and
• Alejandro Perez-Luna

Beilstein J. Org. Chem. 2022, 18, 1256–1263, doi:10.3762/bjoc.18.131

• reagents [22][23] to these substrates was uneventful and allowed for the preparation of 2-furylalkyl (see 3a–c, 4c), -aryl (see 5c, 6c), and -allyl carbinols (see 7c) having furan rings with various triorganosilyl substituents at C3 in a synthetically useful yield and on an appropriate scale (Scheme 2

• from E, and thus affording the C3-lithiated furan derivative G upon 1,4-silyl migration as well as the electrophilic substitution product H in the presence of an appropriate electrophile (Scheme 3, bottom). However, treatment of aldehyde 1b with n-BuLi, followed by addition of benzaldehyde in THF/DMPU

• furan rings, which gave products 25 and 26 in 42% and 40% yield, respectively. Electrophiles other than methallyl chloride could also be used. C3-Allylation of substrate 4c, leading to 27, was achieved in 52% yield by reaction with allyl chloride and in a better 61% yield using allyl bromide. It should

A one-pot electrochemical synthesis of 2-aminothiazoles from active methylene ketones and thioureas mediated by NH₄I

• Shang-Feng Yang,
• Pei Li,
• Zi-Lin Fang,
• Sen Liang,
• Hong-Yu Tian,
• Bao-Guo Sun,
• Kun Xu and
• Cheng-Chu Zeng

Beilstein J. Org. Chem. 2022, 18, 1249–1255, doi:10.3762/bjoc.18.130

• of the phenyl moiety, the corresponding 2-aminothiazoles, 3o–q, were given in 17–53% yields. With electron-withdrawing groups (F, Cl, Br, NO2), the desired products 3r–u were obtained in moderate yields. Other heteroaryl ketones, ethyl 3-(furan-2-yl)-3-oxopropanoate (1v) reacted with thiourea to give

Synthesis of odorants in flow and their applications in perfumery

• Merlin Kleoff,
• Paul Kiler and
• Philipp Heretsch

Beilstein J. Org. Chem. 2022, 18, 754–768, doi:10.3762/bjoc.18.76

• scale [45]. Additionally, Noël and co-workers prepared (+)-sclareolide (3a,6,6,9a-tetramethyl-1,4,5,5a,7,8,9,9b-octahydronaphtho[8,7-d]furan-2-one), a rarely used aromatic odorant reminiscent of cedar and tobacco, by C–H oxidation of (−)-ambroxan (1,5,5,9-tetramethyl-13-oxatricyclo[8.3.0.0(4,9

Complementarity of solution and solid state mechanochemical reaction conditions demonstrated by 1,2-debromination of tricyclic imides

• Petar Štrbac and
• Davor Margetić

Beilstein J. Org. Chem. 2022, 18, 746–753, doi:10.3762/bjoc.18.75

• ] could be simplified by in situ generation of the catalyst. Moreover, in the debromination of norbornene imide 11, the expected Diels−Alder adduct with furan was not obtained, but compound 12 incorporating a tetrahydrofuran ring at position 2, presumably by radical reaction (Figure 2) [19][20]. We

• its synthetic utility were investigated employing various dienes such as furan (18), 1,3-diphenylisobenzofuran (24) (DPIBF) and substituted anthracenes 31, 36 and 39 (Figure 3). Exclusive norbornene exo-π selectivity [24] was observed in all cycloadddition reactions. Selected five-membered dienes were

• subjected to established the Zn/Cu mechanochemical conditions (Figure 3). The furan reaction under ball milling conditions led to a mixture of exo,exo- and exo,endo-cycloadducts 19 and 20 in a 0.8:1 ratio. This is in contrast to classical conditions with the Zn/Ag couple in THF, where the ratio is different

Tri(n-butyl)phosphine-promoted domino reaction for the efficient construction of spiro[cyclohexane-1,3'-indolines] and spiro[indoline-3,2'-furan-3',3''-indolines]

• Hui Zheng,
• Ying Han,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2022, 18, 669–679, doi:10.3762/bjoc.18.68

• . Additionally, the tri(n-butyl)phosphine-promoted domino annulation reaction of isatins and ethyl isatylidene cyanoacetates produced spiro[indoline-3,2'-furan-3',3''-indolines] in satisfactory yields. Keywords: isatin; spiro[cyclohexane-1,3'-indoline]; spiro[indoline-3,2'-furan-3',3''-indoline]; spirooxindole

• employed in the reaction. However, the reaction did not proceed to give the expected spiro[cyclohexane-1,3'-indoline], while a new spiro[indoline-3,2'-furan-3',3''-indoline] was obtained, which was clearly constructed from the annulation reaction of isatin with ethyl isatylidene cyanoacetate. Therefore, we

• turned our attention to the examination of this unprecedented reaction of isatins with ethyl isatylidene cyanoacetates. At last, we successfully found that tri(n-butyl)phosphine promoted the reaction of ethyl isatylidene cyanoacetate 6a and isatin 7a always resulted in spiro[indoline-3,2'-furan-3',3

Direct C–H amination reactions of arenes with N-hydroxyphthalimides catalyzed by cuprous bromide

• Dongming Zhang,
• Bin Lv,
• Pan Gao,
• Xiaodong Jia and
• Yu Yuan

Beilstein J. Org. Chem. 2022, 18, 647–652, doi:10.3762/bjoc.18.65

• the corresponding products in good yields. In addition, employing furan as the substrate, imidation occurred only at the ortho position to provide 3q with a moderate 33% yield. Finally, various substituted N-hydroxyphthalimides were studied (Scheme 3), and the desired N-phthalimide products 3r–u were

Terpenoids from Glechoma hederacea var. longituba and their biological activities

• Dong Hyun Kim,
• Song Lim Ham,
• Zahra Khan,
• Sun Yeou Kim,
• Sang Un Choi,
• Chung Sub Kim and
• Kang Ro Lee

Beilstein J. Org. Chem. 2022, 18, 555–566, doi:10.3762/bjoc.18.58

• = 7.8 Hz), 3.88 (1H, dd, J = 11.9, 2.3 Hz), 3.67 (1H, dd, J = 11.9, 6.1 Hz), 3.29 (1H, overlap), 3.28 (1H, overlap), 3.24 (1H, overlap), and 3.21 (1H, overlap)]. The 13C NMR spectrum of 3 showed 21 carbon signals for five oxygenated carbons (δC 74.5, 68.7 (×2), 61.6, and 61.4), a furan moiety (δC 151.2

Synthesis of sulfur karrikin bioisosteres as potential neuroprotectives

• Martin Pošta,
• Václav Zima,
• Lenka Poštová Slavětínská,
• Marika Matoušová and
• Petr Beier

Beilstein J. Org. Chem. 2022, 18, 549–554, doi:10.3762/bjoc.18.57

• -b]furan-2-one, has been recently identified as an extremely efficient neuroprotective butenolide. Herein, we report the targeted synthesis of this compound as well as new synthetic protocols toward a class of compounds derived from 2H-furo[2,3-c]pyran-2-ones (karrikins) via bioisosteric exchange of

• until recently. In 2019 a study of Naidoo et al. [20] reported naturally occurring karrikins as compounds with moderate inhibitory activity against both types of monoamine oxidases (MAO-A and MAO-B) and acetylcholinesterase, while the sulfur bioiostere 3-methyl-2H-thiopyrano[3,4-b]furan-2-one (8) [21

• ] exhibited excellent activity. No targeted synthesis of 8 exists; it was isolated in low yield as a side-product in the synthesis of KAR1 (1) [21]. In this reaction sequence, thiopyranthione 6b is the side-product in the pyranthione 6a synthesis and both analogues were progressed to the final furan ring

Cs₂CO₃-Promoted reaction of tertiary bromopropargylic alcohols and phenols in DMF: a novel approach to α-phenoxyketones

• Ol'ga G. Volostnykh,
• Olesya A. Shemyakina,
• Anton V. Stepanov and
• Igor' A. Ushakov

Beilstein J. Org. Chem. 2022, 18, 420–428, doi:10.3762/bjoc.18.44

• synthesized α-phenoxyketones 4 in this reaction. The results showed that instead of benzo[b]furan formation, α-ketol rearrangement of phenoxyketones 4a,f occurred to afford β-phenoxyketones 9a,b in 55–60% yields (Scheme 10). Conclusion We have shown that the main direction of the reaction of bromopropargylic

Menadione: a platform and a target to valuable compounds synthesis

• Acácio S. de Souza,
• Ruan Carlos B. Ribeiro,
• Dora C. S. Costa,
• Fernanda P. Pauli,
• David R. Pinho,
• Matheus G. de Moraes,
• Fernando de C. da Silva,
• Luana da S. M. Forezi and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 381–419, doi:10.3762/bjoc.18.43

• -benzoquinones and p-hydroquinones or the synthesis of menadione (10). The furan derivative 34 was used as a diene and 2-iodophenyltrifluoromethanesulfonate (35) as a dienophile, in the presence of n-butyllithium, forming 10 in 55% yield (Scheme 8) [92]. In the same year, Gogin and and co-workers developed a

Effect of a twin-emitter design strategy on a previously reported thermally activated delayed fluorescence organic light-emitting diode

• Ettore Crovini,
• Zhen Zhang,
• Yu Kusakabe,
• Yongxia Ren,
• Yoshimasa Wada,
• Bilal A. Naqvi,
• Prakhar Sahay,
• Tomas Matulaitis,
• Stefan Diesing,
• Ifor D. W. Samuel,
• Wolfgang Brütting,
• Katsuaki Suzuki,
• Hironori Kaji,
• Stefan Bräse and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2021, 17, 2894–2905, doi:10.3762/bjoc.17.197

• )) (10 nm)/X wt % DICzTRZ or ICzTRZ: CzSi (20 nm)/PPF (2,8-bis(diphenylphosphoryl)dibenzo[b,d]furan) (5 nm)/TPBi (1,3,5-tris(1-phenyl-1H-benzo[d]imidazol-2-yl)benzene) (50 nm)/Liq (lithium quinolin-8-olate) (1 nm)/Al (80 nm), where X is 20 or 30. The PVK layer is applied to facilitate hole injection from

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

• the furan framework. Following Fe-catalyzed oxidation, the resulting oxonium cation can be deprotonated to afford the final dihydrofuran. Further, this inter-/intramolecular radical addition/cyclization methodology has been applied for the synthesis of various substituted dihydropyrans [100][101] and

Photophysical, photostability, and ROS generation properties of new trifluoromethylated quinoline-phenol Schiff bases

• Inaiá O. Rocha,
• Yuri G. Kappenberg,
• Wilian C. Rosa,
• Clarissa P. Frizzo,
• Nilo Zanatta,
• Marcos A. P. Martins,
• Isadora Tisoco,
• Bernardo A. Iglesias and
• Helio G. Bonacorso

Beilstein J. Org. Chem. 2021, 17, 2799–2811, doi:10.3762/bjoc.17.191

• ; 19F NMR (565 MHz, CDCl3) δ −61.66 (CF3); FTIR (ATR) ν: 3085 (ν OH), 1625 (ν CH=N), 1113 (ν C-O) cm−1; HRMS–ESI (m/z): [M + H]+ calcd for C23H15F3N3O3, 438.1060; found, 438.1059. (E)-2-(((2-(Furan-2-yl)-4-(trifluoromethyl)quinolin-6-yl)imino)methyl)phenol (3fa): Brown solid, yield 80%; mp 205–209 °C

N-Sulfinylpyrrolidine-containing ureas and thioureas as bifunctional organocatalysts

• Viera Poláčková,
• Dominika Krištofíková,
• Boglárka Némethová,
• Renata Górová,
• Mária Mečiarová and
• Radovan Šebesta

Beilstein J. Org. Chem. 2021, 17, 2629–2641, doi:10.3762/bjoc.17.176

• compounds with heterocyclic substituents are of high biological and medicinal relevance [34][35]. Therefore, we have decided to evaluate sulfinylurea and thiourea catalysts C1 and C2 also with (E)-2-(2-nitrovinyl)furan (9) and (E)-3-(2-nitrovinyl)pyridine (11) as Michael acceptors. As Michael donor, we

• chose 3-phenylpropanal (6c). The Michael addition of 3-phenylpropanal (6c) with (E)-2-(2-nitrovinyl)furan (9) under initial reaction conditions with (S,R)-C1 (10 mol %) in THF/H2O with NMM as the base and with PhCO2H as acid additive gave product 10a in 31% yield after 72 hours with a diastereomeric

• )-2-(2-nitrovinyl)furan (9) and they provided racemic adduct 12 in 14 or 64% yield with poor or no diastereoselectivity (Table 2, entries 1 and 2). The change of solvent made it possible to obtain the products in a shorter time. Reactions catalyzed with 3 mol % (S,R)-C1 and (S,S)-C1 in MeCN gave

Recent advances in the tandem annulation of 1,3-enynes to functionalized pyridine and pyrrole derivatives

• Yi Liu,
• Puying Luo,
• Yang Fu,
• Tianxin Hao,
• Xuan Liu,
• Qiuping Ding and
• Yiyuan Peng

Beilstein J. Org. Chem. 2021, 17, 2462–2476, doi:10.3762/bjoc.17.163

• ][28][29]. In industry, pyrrole mainly comes from the extraction of coal tar, the condensation reaction of furan and ammonia under high temperature, or the cascade cyclization reaction of acetylene, formaldehyde, and ammonia. In the laboratory, there are many efficient methods for the synthesis of

• reaction of 2-trifluoromethyl-1,3-enynes 36 with aliphatic primary amines and the following NXS-mediated oxidative cyclization (Scheme 13) [57]. The method tolerated various substituted benzylamines, 2-phenylethanamines, isopropylamine, and other aliphatic chain-like amines. Furthermore, both furan-2

Strategies for the synthesis of brevipolides

• Yudhi D. Kurniawan and
• A'liyatur Rosyidah

Beilstein J. Org. Chem. 2021, 17, 2399–2416, doi:10.3762/bjoc.17.157

• -dihydro-α-pyrone derivatives, bearing either a distinctive cyclopropane or furan ring and named brevipolides A–O (1–15), have been isolated from the invasive plant Hyptis brevipes Poit. Their fascinating structural features, and the potent biological activities, including cytotoxicity against an array of

• the hydrogen source. Following protection of the alcohol moiety with PMBCl, ether 22 was realized in 93% yield. Afterwards, this species was transformed into the γ-keto α,β-unsaturated aldehyde 23 through an NBS-assisted furan oxidation procedure in moderate yield (65%). The keto functionality was

• cyclization to form the furan ring is then expected to occur concurrently. (−)-Diethyl tartrate (98) was eventually selected as the precursor to construct the unsaturated ester 96 after a double two-carbon homologation. In the reverse order, the synthesis of 13 began with the conversion of diethyl tartrate 98

Advances in mercury(II)-salt-mediated cyclization reactions of unsaturated bonds

• Sumana Mandal,
• Raju D. Chaudhari and
• Goutam Biswas

Beilstein J. Org. Chem. 2021, 17, 2348–2376, doi:10.3762/bjoc.17.153

• furylmercurials 91 via syn-addition of acetylene, which on carbonylation yielded the furan-containing carbonyl compound 92 (Scheme 30) [83]. It was proposed that initially mercuration of acetylene bonds via mercurinium like ions or π-complex takes place. Then the structure was stabilized through hydrogen bonding

• between alcohol and carbonyl groups (path a) or by hemiketal formation (path b). Thus, the chloride ion attacks from the frontside, producing syn-addition molecules that, upon dehydration, formed furan rings. Later they had reported similar mercuration of arylacetylenes to synthesize a broad spectrum of

• cyclization of secondary and tertiary l-alkynyl-2,3-epoxyalcohols 131a [94]. This is an example of a Hg(II)-salt-catalyzed rearrangement of 1-alkynyl-2,3-epoxy alcohols to substituted furans. The furan 133a was formed by dehydration of intermediate 132a through the corresponding oxonium cation. When R3 is an

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

• brominated naphthalene 153 with PhLi yielded compound 154, which collapsed to naphthotriyne 155 at elevated temperatures. Sequential addition of furan generated the trisadduct 156. Then, dibenz[a,c]anthracene 158 was obtained in good yield (86%) in two steps by hydrogenation of 156 and further dehydration of

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

• amiodarone (93, antiarrhythmic activity) (Scheme 32A) [166]. The method consists of a tandem, regioselective Fe(III)-catalyzed C–H halogenation, followed by an Fe or Cu-catalyzed O-arylation to access the benzo[b]furan derivatives in high yields. Several natural products and pharmacologically active targets

• bearing the furan ring were synthesized in moderate to good yields. Overall, the new protocol presented a broad scope and excellent functional group tolerance, allowing the synthesis of valuable molecules like corsifuran C (94), moracin F (95), and caleprunin B (96) (Scheme 32D). In 2020, Chattopadhyay

Chemical approaches to discover the full potential of peptide nucleic acids in biomedical applications

• Nikita Brodyagin,
• Martins Katkevics,
• Venubabu Kotikam,
• Christopher A. Ryan and
• Eriks Rozners

Beilstein J. Org. Chem. 2021, 17, 1641–1688, doi:10.3762/bjoc.17.116

• precursors in vitro [133]. Furan (F, Figure 8) as a reactive nucleobase mimic was well accommodated in a duplex with DNA without decreasing its thermal stability [134]. Upon oxidation of the furan ring, F-modified PNAs reacted preferentially with cytosine and adenine and irreversibly crosslinked with ssDNA

Recent advances in the application of isoindigo derivatives in materials chemistry

• Andrei V. Bogdanov and
• Vladimir F. Mironov

Beilstein J. Org. Chem. 2021, 17, 1533–1564, doi:10.3762/bjoc.17.111

• arrangement of the isoindigo and DPP fragments relative to each other was demonstrated [96]. Thus, the dihedral angle 179° in a furan polymer determines the conductivity μh/μe = 0.01 cm2⋅V−1⋅s−1/1.6⋅10−3 cm2⋅V−1⋅s−1, while polymers containing thiophene or p-phenylene spacers did not possess conductivity at

Cascade intramolecular Prins/Friedel–Crafts cyclization for the synthesis of 4-aryltetralin-2-ols and 5-aryltetrahydro-5H-benzo[7]annulen-7-ols

• Jie Zheng,
• Shuyu Meng and
• Quanrui Wang

Beilstein J. Org. Chem. 2021, 17, 1481–1489, doi:10.3762/bjoc.17.104

• [10][11][12][13][14]. For example, Nagumo and coworkers have developed a Prins/Friedel–Crafts cyclization of homocinnamyl alcohols with aromatic aldehydes under the action of BF3·Et2O affording 2H-indeno[1,2-b]furan derivatives [15]. Likewise, Hinkle and coworkers reported in 2017 a three-step domino

• diastereoselectivity (cis/trans ratio = 1:99). The preferential formation of the trans-configured products for furan nucleophiles may be due to the fact that the addition of furan is reversible leading to equilibration to the more stable trans product. To test this hypothesis, we monitored the reaction by HPLC (Table

• , the reactions with other 2-(2-vinylphenyl)ethanals 13b–g carrying different substituents on the benzene ring or on the side chain with veratrole and furan as the nucleophiles were investigated. As can be seen from Scheme 7, under comparable conditions, most reactions proceeded smoothly with the