[2 + 1] Cycloaddition reactions of fullerene C₆₀ based on diazo compounds

• Yuliya N. Biglova

Beilstein J. Org. Chem. 2021, 17, 630–670, doi:10.3762/bjoc.17.55

• series of spiromethanofullerenes was synthesized using various diazo derivatives. For example, compounds spiro-bound with glycosides are the first chiral and enantiomerically pure derivatives of fullerenes 71 and 72 (Scheme 22) [107]. It should be noted that though a considerable amount of information on

• the synthesis of various spiromethanofullerenes. For example, spiro derivatives 73–75 were obtained in one of the first works on this subject (Figure 7). The authors obtained quinone-derived [6,6]-closed spiromethanofullerenes 76–78 by reactions of C60 with the corresponding diazo compounds upon

• heating, or photochemically in a nitrogen atmosphere (Scheme 23) [109]. The reaction of spiro[10-anthron-9,61'-methanofullerene] (79) [110] with bis(trimethylsilyl)carbodiimide and malononitrile in pyridine in the presence of TiCl4 resulted in spirocyclic blocks 80 and 81, respectively (Scheme 24) [111

Diels–Alder reaction of β-fluoro-β-nitrostyrenes with cyclic dienes

• Savva A. Ponomarev,
• Roman V. Larkovich,
• Alexander S. Aldoshin,
• Andrey A. Tabolin,
• Sema L. Ioffe,
• Jonathan Groß,
• Till Opatz and
• Valentine G. Nenajdenko

Beilstein J. Org. Chem. 2021, 17, 283–292, doi:10.3762/bjoc.17.27

• dispersion effects are not included, whereas M062X includes nonlocal effects of electronic dispersion [70][75]. We also demonstrate the preparation of norbornene structures substituted at the methylene bridge. The reaction of model nitrostyrene 1h with spiro[2.4]hepta-4,6-diene was carried out (Scheme 2). As

• °C) and CHD at 110 °C. Scope of the nitrostyrenes 1 in the Diels–Alder reaction with CPD (dr = exo:endo). The Diels–Alder reaction of nitrostyrene 1h with spiro[2.4]hepta-4,6-diene. Diels–Alder reaction of nitrostyrenes 1 with CHD (dr = exo:endo). (а) Reaction under microwave activation. Kinetic

The preparation and properties of 1,1-difluorocyclopropane derivatives

• Kymbat S. Adekenova,
• Peter B. Wyatt and
• Sergazy M. Adekenov

Beilstein J. Org. Chem. 2021, 17, 245–272, doi:10.3762/bjoc.17.25

• reagent was also used for the synthesis of organic spiro compounds, containing selectively fluorinated cyclopropanes 38a,b [45], for the preparation of 6,6-difluoro-3-azabicyclo[3.1.0]hexane (39) (on a 10 g scale) [46], and of the epothilone B analog 40 [47] (Table 2). The reagents (chlorodifluoromethyl

All-carbon [3 + 2] cycloaddition in natural product synthesis

• Zhuo Wang and
• Junyang Liu

Beilstein J. Org. Chem. 2020, 16, 3015–3031, doi:10.3762/bjoc.16.251

• in natural product synthesis reported from 2011–2020 (inclusive). The intermolecular all-carbon [3 + 2] cycloaddition offers a facile approach to install functionalized five-carbon carbocycles, including fused-rings (e.g., longeracinphyllin A (10)) and/or spiro-ring (e.g., marcfortine B (8)), at

• enantioselective synthesis of marcfortine C (9, Scheme 4B). Another brilliant example is the development of a chiral-phosphine-catalyzed [3 + 2] annulation reported by Lu in 2019, in which the chiral phosphine catalyst confers high stereocontrol on the formation of a spiro adduct bearing two vicinal all-carbon

• product synthesis. (A) Synthesis of longeracinphyllin A (10) [41]. (B) Synthesis of daphenylline (11) [42]. (C) Synthesis of daphenylline (11) [43]. (A) Phosphine-catalyzed [3 + 2] annulation of unsymmetric isoindigo 100 with allene in the preparation of spiro adduct 103 [46]. (B) The proposed catalytic

Bifurcated synthesis of methylene-lactone- and methylene-lactam-fused spirolactams via electrophilic amide allylation of γ-phenylthio-functionalized γ-lactams

• Tetsuya Sengoku,
• Koki Makino,
• Ayumi Iijima,
• Toshiyasu Inuzuka and
• Hidemi Yoda

Beilstein J. Org. Chem. 2020, 16, 2769–2775, doi:10.3762/bjoc.16.227

• -lactone derivatives spiro-fused to an oxindole (A), one of which exhibited a potent cytotoxic activity [9]. Our research group succeeded the enantiopure synthesis of these compounds, in which enantioselective allylation of an isatin derivative with an amido-functionalized allylstannane was employed as a

• key reaction (Scheme 1b) [10][11]. More recently, an amide-functionalized allyl boronate was developed as an alternative reagent for the allylstannane [12][13][14][15][16], which led to the syntheses of not only cytotoxic methylene-lactones spiro-fused to a lactam ring (B) but also their analogous

• the construction of the spiro skeleton of 4 and 5. For this purpose, we initially attempted to transform 3b to 5a through the reaction sequence consisting of copper-mediated hydroxylation and acid-mediated lactonization based on our previous reports [10][11][14][21]. Substitution of the phenylthio

Synthetic approaches to bowl-shaped π-conjugated sumanene and its congeners

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 2212–2259, doi:10.3762/bjoc.16.186

Lipophilicity trends upon fluorination of isopropyl, cyclopropyl and 3-oxetanyl groups

• Benjamin Jeffries,
• Zhong Wang,
• Robert I. Troup,
• Anaïs Goupille,
• Jean-Yves Le Questel,
• Charlene Fallan,
• James S. Scott,
• Elisabetta Chiarparin,
• Jérôme Graton and
• Bruno Linclau

Beilstein J. Org. Chem. 2020, 16, 2141–2150, doi:10.3762/bjoc.16.182

• drugs with such substructures include Voxilaprevir and Glecaprevir. Finally, it is useful to consider the lipophilicity changes upon extending a propyl or ethyl chain to a cyclopropylmethyl moiety, which represents a one-carbon and a two-carbon extension, respectively. It is known that adding a spiro

Azidophosphonium salt-directed chemoselective synthesis of (E)/(Z)-cinnamyl-1H-triazoles and regiospecific access to bromomethylcoumarins from Morita–Baylis–Hillman adducts

• Soundararajan Karthikeyan,
• Radha Krishnan Shobana,
• Kamarajapurathu Raju Subimol,
• J. Helen Ratna Monica and
• Ayyanoth Karthik Krishna Kumar

Beilstein J. Org. Chem. 2020, 16, 1579–1587, doi:10.3762/bjoc.16.130

• -lactams [6], quinolin-5-ones [7], spirobisglutarimides [8], indolizines [9], and spiro carbocyclic frameworks [10]. However, most of the reported synthetic transformations utilize either allylic hydroxy-protected or allyl halide-substituted MBH adducts [11][12][13][14][15][16][17][18][19][20][21][22][23

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

• expansion of vinyl spiro epoxides. Disulfide-catalyzed aerobic oxidation of diarylacetylene. Disulfide-catalyzed aerobic photooxidative cleavage of olefins. Disulfide-catalyzed aerobic oxidation of 1,3-dicarbonyl compounds. Proposed mechanism of the disulfide-catalyzed aerobic oxidation of 1,3-dicarbonyl

Recent synthesis of thietanes

• Jiaxi Xu

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

• intermediate for the total synthesis of sesquiterpene thioalkaloids (Scheme 3). Spiro[3.3]heptane derivatives were recently used as the surrogates of piperazines, piperidines, morpholines, and thiomorpholines, which display pharmacological activities [35]. 1,6-Thiazaspiro[3.3]heptane (24) was synthesized for

• series of thietanose nucleosides 118 [53]. Similarly, enatiomeric thietanose nucleosides 123 were prepared from L-xylose [53] (Scheme 24). In 2010, Takahata and co-workers designed and synthesized thietane-fused nucleosides. They first prepared a key intermediate spiro acetal 125, which was converted

[3 + 2] Cycloaddition with photogenerated azomethine ylides in β-cyclodextrin

• Margareta Sohora,
• Leo Mandić and
• Nikola Basarić

Beilstein J. Org. Chem. 2020, 16, 1296–1304, doi:10.3762/bjoc.16.110

• , 1C), 30.1 (t, 1C), 26.2 (t, 1C), 23.7 (t, 1C), 21.3 (t, 1C); MS m/z (% relative intensity): 229 (100), 230 (15.1), 231 (1.1). 1,6-Dioxo-1,4,5,6-tetrahydro-2H-spiro[benzo[c]azocine-3,1'-cyclohexane]-5-carbonitrile (9): 3 mg (3%), oily crystals; 1H NMR (CD3OD, 300 MHz) δ 8.19-8.15 (m, 1H), 8.04–8.00 (m

A cyclopeptide and three oligomycin-class polyketides produced by an underexplored actinomycete of the genus Pseudosporangium

• Shun Saito,
• Kota Atsumi,
• Tao Zhou,
• Keisuke Fukaya,
• Daisuke Urabe,
• Naoya Oku,
• Md. Rokon Ul Karim,
• Hisayuki Komaki and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2020, 16, 1100–1110, doi:10.3762/bjoc.16.97

• to C-26 was then connected at C-20 by HMBC correlations from H3-39 to C-19, C-20, and C-21. The carbon chain was further extended from C-26, via the spiro carbon C-27 (δC 98.6) and a methylene C-29, to the terminal methyl C-34 on the basis of COSY and HMBC correlations. Finally, an HMBC correlation

• from the oxymethine H-25 to C-1 established a macrolactone structure, and a spiroacetal structure with two six-membered rings was deduced from a series of HMBC correlations of the protons in the spiro rings to C-27, illustrating the oligomycin-class structure. The remaining six carbons from C-42 to C

Cation-induced ring-opening and oxidation reaction of photoreluctant spirooxazine–quinolizinium conjugates

• Phil M. Pithan,
• Sören Steup and
• Heiko Ihmels

Beilstein J. Org. Chem. 2020, 16, 904–916, doi:10.3762/bjoc.16.82

• for the development of photochromic chemosensors that allow the colorimetric or fluorimetric detection of particular analytes [5][29][35][36][37][38][39][40][41]. Furthermore, studies of such spiro derivatives [16][42][43], specifically spiroindolinonaphthoxazines [44][45][46][47], have shown that the

Diversity-oriented synthesis of 17-spirosteroids

• Benjamin Laroche,
• Thomas Bouvarel,
• Martin Louis-Sylvestre and
• Bastien Nay

Beilstein J. Org. Chem. 2020, 16, 880–887, doi:10.3762/bjoc.16.79

• imposed by the steroid skeleton on the dienyl tetrahydrofuran α-face, imposing orbital interactions with the dienophile from the β-face (Figure 3b). All these structures have an extended skeleton, with the steroid part being perpendicular to the cycloadduct moiety thanks to the spiro junction. Conclusion

Combining enyne metathesis with long-established organic transformations: a powerful strategy for the sustainable synthesis of bioactive molecules

• Valerian Dragutan,
• Ileana Dragutan,
• Albert Demonceau and
• Lionel Delaude

Beilstein J. Org. Chem. 2020, 16, 738–755, doi:10.3762/bjoc.16.68

• installation of the1,3-diene units at the anomeric center of the future C-aryl glycoside (23) in high yields (94–98%, Scheme 24). Alternatively, an intramolecular enyne metathesis promoted by the first-generation Grubbs catalyst produced the spiro-C-aryl glycoside 24 from sugar enyne precursors (Scheme 25

• ). Subsequent Diels–Alder cycloaddition reactions with dienophiles and further aromatization reactions paved the way for a convenient access to structurally diverse polycyclic compounds. For instance, installing the C-aryl and spiro-C-aryl glycosides in the same moiety was successfully achieved. An application

• . Synthesis of spiro-C-aryl glycoside 24 by a tandem intramolecular enyne metathesis/Diels–Alder reaction/aromatization. Pathways to (−)-exiguolide (25) by Trost’s Ru-catalyzed enyne cross-coupling and cross-metathesis [94]. Funding Support from the Romanian Academy and from Wallonie-Bruxelles International

Recent advances in Cu-catalyzed C(sp³)–Si and C(sp³)–B bond formation

• Balaram S. Takale,
• Ruchita R. Thakore,
• Elham Etemadi-Davan and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2020, 16, 691–737, doi:10.3762/bjoc.16.67

• carbenoid insertions using spiro-bisimine ligand L25 at cryogenic temperatures (Scheme 39A). Ollevier, however, focused on making these reactions more general under ligand-free conditions at ambient temperature, and without the asymmetric component (Scheme 39B). The substrate scope was already broad

Synthesis of organic liquid crystals containing selectively fluorinated cyclopropanes

• Zeguo Fang,
• Nawaf Al-Maharik,
• Peer Kirsch,
• Matthias Bremer,
• Alexandra M. Z. Slawin and
• David O’Hagan

Beilstein J. Org. Chem. 2020, 16, 674–680, doi:10.3762/bjoc.16.65

• (Figure 2). Therefore, the aim of the study was to prepare these target liquid crystals and evaluate their properties relative to each other, to establish if there were any obvious structure–activity relationships to emerge for the design of positive or negative dielectric materials. Also the fixed spiro

• . The synthesis of the diastereoisomers of spiro LC candidates 11a and 11b also started from ketone 15 as illustrated in Scheme 4. Treatment of ketone 15 with methylenetriphenylphosphine which was generated in situ from methyltriphenylphosphonium bromide (PPh3CH3Br), generated exo-methylene cyclohexane

• , 9 and 10, were found to be small, whereas the spiro-cyclopropane 11a had a significantly, decreased Δn. As discussed, either positive or negative dielectric anisotropy is an important parameter related to the driving voltage of LC displays and in order to reduce energy consumption, good materials

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

• esters with AgSCF3 for the synthesis of trifluoromethylthiolated coumarins (Scheme 1b) [28]. In 2016, Liu exploited the tandem trifluoromethylthiolation/cyclization of N-arylpropiolamides to construct the SCF3-substituted spiro[4,5]trienones (Scheme 1c) [29]. In the same year, Zhang and Chen disclosed

Synthesis of six-membered silacycles by borane-catalyzed double sila-Friedel–Crafts reaction

• Yafang Dong,
• Masahiko Sakai,
• Kazuto Fuji,
• Kohei Sekine and
• Yoichiro Kuninobu

Beilstein J. Org. Chem. 2020, 16, 409–414, doi:10.3762/bjoc.16.39

• 9,9-dihydro-5-silafluorene (2f), which gave the spiro-type phenoxasilin 3f in 96% yield. We then investigated the scope of the starting biaryl ethers used in the reaction as well as related derivatives thereof using dihydrodiphenylsilane (2a, Scheme 3). Pyrrolidine-substituted diaryl ether 1b was

Architecture and synthesis of P,N-heterocyclic phosphine ligands

• Wisdom A. Munzeiwa,
• Bernard Omondi and
• Vincent O. Nyamori

Beilstein J. Org. Chem. 2020, 16, 362–383, doi:10.3762/bjoc.16.35

• -oxazaphosphorine ligands with a P-center and backbone chirality (Scheme 24). Spiro-1,3-amino alcohol compounds 124 were synthesized according to a literature procedure [107]. For the synthesis of the mono-N-methylated amino alcohol ligands a cooled solution of dichlorophenylphosphine was treated with triethylamine

• and mono-N-methylated spiro 1,3-amino alcohols 124. The mixture was equilibrated under reflux allowing P-center inversion and an uneven mixture of diastereoisomers 125 and 127 was obtained. Treating the mixture with borane·dimethyl sulfide gave a mixture of diastereoisomers in a ratio of 2:5. The

• protocol with free amine spiro-amino alcohol derivative 124 gave compounds 125 and 127 (R = H) in low yields. An optimized procedure was used where dichlorophenylphosphine and borane·dimethyl sulfide in tetrahydrofuran were premixed at −78 °C. The temperature was then raised to 25 °C before neutralizing

Combination of multicomponent KA² and Pauson–Khand reactions: short synthesis of spirocyclic pyrrolocyclopentenones

• Riccardo Innocenti,
• Elena Lenci,
• Gloria Menchi and
• Andrea Trabocchi

Beilstein J. Org. Chem. 2020, 16, 200–211, doi:10.3762/bjoc.16.23

• approach. The polyfunctional molecular scaffolds were tested on the cyclopentenone reactivity to further expand the skeletal diversity, demonstrating the utility of this combined approach in generating novel spiro compounds as starting material for the generation of chemical libraries. The chemoinformatics

• Pauson–Khand conditions (Table 1,entry 14). The synthetic utility of the spiro derivatives resulting from the combined KA2/Pauson–Khand process to generate second-generation molecular scaffolds was tested on compound 5 by applying representative reactions on the enone structural motif (Scheme 3). The

• even more efficient in increasing the three-dimensional character of these compounds, as spiro tricyclic products were found to be more shifted towards the sphere-disc region of this chemical space, especially if compared to their corresponding starting materials (see Figure 4, compounds 5 and 26 with

Facile regiodivergent synthesis of spiro pyrrole-substituted pseudothiohydantoins and thiohydantoins via reaction of [e]-fused 1H-pyrrole-2,3-diones with thiourea

• Aleksandr I. Kobelev,
• Nikita A. Tretyakov,
• Ekaterina E. Stepanova,
• Maksim V. Dmitriev,
• Michael Rubin and
• Andrey N. Maslivets

Beilstein J. Org. Chem. 2019, 15, 2864–2871, doi:10.3762/bjoc.15.280

• , Kansas 66045, United States Department of Chemistry, North Caucasus Federal University, ul. Pushkina 1a, Stavropol 355009, Russian Federation 10.3762/bjoc.15.280 Abstract A highly divergent synthesis of regioisomeric thiohydantoins and pseudothiohydantoins spiro-fused to a pharmacologically valuable

• pyrrole-2-one fragment involving the reaction of [e]-fused 1H-pyrrole-2,3-diones with thioureas was developed. The obtained spiro pseudothiohydantoin derivatives were found to undergo a pseudothiohydantoin–thiohydantoin rearrangement. The reactions were shown to proceed under catalyst-free conditions in

• rearrangement (PTR, Scheme 1) [8][9][10][11], which is a special case of a quite poorly investigated iminothiolactone–thiolactam rearrangement [12][13][14][15][16]. This reaction offers attractive opportunities for the design of libraries of regioisomeric hydantoin-based compounds for drug discovery. Spiro

Diversity-oriented synthesis of spirothiazolidinediones and their biological evaluation

• Sambasivarao Kotha,
• Gaddamedi Sreevani,
• Lilya U. Dzhemileva,
• Milyausha M. Yunusbaeva,
• Usein M. Dzhemilev and
• Vladimir A. D’yakonov

Beilstein J. Org. Chem. 2019, 15, 2774–2781, doi:10.3762/bjoc.15.269

• inducers in the HeLa, Hek293, U937, Jurkat, and K562 cell lines. Keywords: apoptosis; biologically active; [2 + 2 + 2] cycloaddition; flow cytometry; spiro thiazolidinedione; Introduction Heterocyclic compounds play a vital role in the metabolism of all living cells. Thus, most of the biologically active

• synthesis of thiazolidinedione derivatives is refluxing chloroacetic acid (2) with thiourea (1), followed by a Knoevenagel condensation with an aldehyde (Scheme 1) [25]. Results and Discussion Limited reports are available dealing with the synthesis of spiro derivatives of thiazolidine-2,4-diones [26][27

• bromide (6a) in the presence of Mo(CO)6 in acetonitrile at 90 °C under microwave irradiation (MWI) conditions to give the co-trimerized spiro derivative 8a (Scheme 2). The free NH moiety of thiazolidinedione 3 was alkylated using alkyl or aryl halides in the presence of Et3N using DCM as solvent. To our

Sugar-derived oxazolone pseudotetrapeptide as γ-turn inducer and anion-selective transporter

• Sachin S. Burade,
• Sushil V. Pawar,
• Tanmoy Saha,
• Navanath Kumbhar,
• Amol S. Kotmale,
• Manzoor Ahmad,
• Pinaki Talukdar and
• Dilip D. Dhavale

Beilstein J. Org. Chem. 2019, 15, 2419–2427, doi:10.3762/bjoc.15.234

• conformation [5]. Amongst these, the use of sugar-derived TAAs in peptidomimetics is less explored. The linear tri-/tetrapeptides and spiro-peptides at the anomeric position of mannofructose are known [6][7][8]. Stick and co-workers have reported the synthesis of tetrasubstituted sugar furanoid amino acid

Recent advances in transition-metal-catalyzed incorporation of fluorine-containing groups

• Xiaowei Li,
• Xiaolin Shi,
• Xiangqian Li and
• Dayong Shi

Beilstein J. Org. Chem. 2019, 15, 2213–2270, doi:10.3762/bjoc.15.218

• co-workers [71] described the one-pot asymmetric gem-chlorofluorination of active methylene compounds by using a copper(II) complex with a chiral spiro 2-pyridyl monooxazoline ligand (SPYMOX). The corresponding α-chloro-α-fluoro-β-keto esters were isolated with up to 92% ee (Scheme 29a). This