Thiophene/selenophene-based S-shaped double helicenes: regioselective synthesis and structures

• Mengjie Wang,
• Lanping Dang,
• Wan Xu,
• Zhiying Ma,
• Liuliu Shao,
• Guangxia Wang,
• Chunli Li and
• Hua Wang

Beilstein J. Org. Chem. 2022, 18, 809–817, doi:10.3762/bjoc.18.81

• resulted in oxidative photocyclization products with two types of configurations wherein two benzene rings were closed in the same and opposite direction, such as DH-1–3 and 6 (Figure 2). However, after the double oxidative photocyclizations of 5a–c in the presence of iodine and propylene oxide in dry

• toluene (6 mL), iodine (7.3 mg, 0.028 mmol, 2.0 equiv) and excess propylene oxide were added. The reaction solution was irradiated with a 450 W unfiltered Hg medium-pressure lamp for 1.5 h. The reaction was quenched with saturated Na2SO3 solution (5 mL). The reaction mixture was extracted with CH2Cl2 (3

Constrained thermoresponsive polymers – new insights into fundamentals and applications

• Patricia Flemming,
• Alexander S. Münch,
• Andreas Fery and
• Petra Uhlmann

Beilstein J. Org. Chem. 2021, 17, 2123–2163, doi:10.3762/bjoc.17.138

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

α,γ-Dioxygenated amides via tandem Brook rearrangement/radical oxygenation reactions and their application to syntheses of γ-lactams

• Mikhail K. Klychnikov,
• Radek Pohl,
• Ivana Císařová and
• Ullrich Jahn

Beilstein J. Org. Chem. 2021, 17, 688–704, doi:10.3762/bjoc.17.58

• enantiomerically pure (S)-propylene oxide ((S)-7b) the dioxygenated amides (2R,4S)-9i–k were predominately formed with 3:1 anti/syn diastereoselectivity in the radical coupling with TEMPO irrespective of the aryl substituent (Table 2, entries 9, 11, and 12), whereas the sequence of amide 8e with (R)-propylene

• chiral cyclic amide substituent on the nitrogen atom influences the selectivity of the radical coupling with TEMPO to some extent, though less than the 1-arylethyl groups. Somewhat surprisingly, amides 8h,i did not react with propylene oxide 7b neither at 0 °C nor at room temperature. In order to confirm

• silyloxy group in γ-position nor the size of the N-substituent influence the diastereoselectivity of radical coupling with TEMPO (3). In contrast, the chiral N-(1-phenylethyl)- and N-(1-naphthylethyl)-substituted amides 9i–k were obtained from (S)-propylene oxide (S)-7b with moderate 3:1 anti/syn

Valorisation of plastic waste via metal-catalysed depolymerisation

• Francesca Liguori,
• Carmen Moreno-Marrodán and
• Pierluigi Barbaro

Beilstein J. Org. Chem. 2021, 17, 589–621, doi:10.3762/bjoc.17.53

• hydrogenolysis to give PD in 99% yield at 160 °C, 54 bar H2 and in anisole/THF solvent [182][188]. PD is a safe chemical that is mainly produced from propylene oxide or catalytically from lactic acid intermediate, and it serves in the polymer and food industry or as antifreezing agent [276][277]. Under milder

The charge-assisted hydrogen-bonded organic framework (CAHOF) self-assembled from the conjugated acid of tetrakis(4-aminophenyl)methane and 2,6-naphthalenedisulfonate as a new class of recyclable Brønsted acid catalysts

• Svetlana A. Kuznetsova,
• Alexander S. Gak,
• Yulia V. Nelyubina,
• Vladimir A. Larionov,
• Han Li,
• Michael North,
• Vladimir P. Zhereb,
• Alexander F. Smol'yakov,
• Artem O. Dmitrienko,
• Michael G. Medvedev,
• Igor S. Gerasimov,
• Ashot S. Saghyan and
• Yuri N. Belokon

Beilstein J. Org. Chem. 2020, 16, 1124–1134, doi:10.3762/bjoc.16.99

• , reverting to the F-1a phase with nine molecules of water for every two residues of TAPM within 10–20 minutes of atmospheric exposure. In addition, F-1 reversibly took up methanol (1.5 molecules per TAPM moiety), benzene (4–5 molecules per TAPM), and propylene oxide (1.5 molecules per TAPM) in a closed

• opening. Other epoxides were also studied as substrates for the three-phase ring-opening with water (Table 2, runs 6–9). Propylene oxide and butylene oxide were good substrates for the reaction (Table 2, runs 6 and 7), but hex-1-ene oxide was almost unreactive (Table 2, runs 8 and 9), indicating that some

Recent advances in photocatalyzed reactions using well-defined copper(I) complexes

• Mingbing Zhong,
• Xavier Pannecoucke,
• Philippe Jubault and
• Thomas Poisson

Beilstein J. Org. Chem. 2020, 16, 451–481, doi:10.3762/bjoc.16.42

• 2012, Collins and co-workers described a copper-catalyzed photocyclization to synthesize [5]helicene (Scheme 29) [43]. Using the in situ-formed [Cu(I)(dmp)(xantphos)]BF4 (25 mol %) in the presence of iodine and propylene oxide as the oxidant system under visible light irradiation, [5]helicene was

• and propylene oxide as a proton scavenger under flow conditions (0.05 mL/min; residence time = 20 h). The use of flow conditions drastically enhanced the kinetics of the reaction, moving from 120 h reaction time in batch to 20 h using a continuous flow reactor. The reaction allowed the synthesis of a

Reaction of oxiranes with cyclodextrins under high-energy ball-milling conditions

• László Jicsinszky,
• Federica Calsolaro,
• Katia Martina,
• Fabio Bucciol,
• Maela Manzoli and
• Giancarlo Cravotto

Beilstein J. Org. Chem. 2019, 15, 1448–1459, doi:10.3762/bjoc.15.145

• derivatisation method that uses low-boiling epoxide reagents in a high-energy ball mill (HEBM). The simplified preparation and purification of low substitution-degree common (2-hydroxy)propylated β- and γ-cyclodextrins (β/γ-CDs) has been realised. The intelligent use of propylene oxide has also facilitated the

• solubility of β-CD can be dramatically increased using a base, which occurs via the ionisation of the secondary hydroxy groups, near pH ≈12 (secondary hydroxy dissociation starts around ≈11.5–11.8 in water) [4][5]. In basic aqueous medium, the high reactivity and low water-miscibility of 1,2-propylene oxide

• removed (by aluminium oxide) and “recrystallisation” (from acetone) eliminates (oligo)-PG to a pharmaceutically acceptable level [6][7]. However, the low boiling point of the 1,2-propylene oxide generates some safety concerns. The low reaction temperature favours the secondary hydroxy group in CD

Synthesis of polydicyclopentadiene using the Cp₂TiCl₂/Et₂AlCl catalytic system and thin-layer oxidation of the polymer in air

• Zhargolma B. Bazarova,
• Ludmila S. Soroka,
• Alex A. Lyapkov,
• Мekhman S. Yusubov and
• Francis Verpoort

Beilstein J. Org. Chem. 2019, 15, 733–745, doi:10.3762/bjoc.15.69

• toluene solution of the monomer. However, before adding the catalytic complex, the monomer solution was placed in an adiabatic mixing reactor until the temperature was stabilized. To limit the development of the polymer chain and as a deactivator of the catalyst system, propylene oxide was used. The

Synthesis of the polyketide section of seragamide A and related cyclodepsipeptides via Negishi cross coupling

• Jan Hendrik Lang and
• Thomas Lindel

Beilstein J. Org. Chem. 2019, 15, 577–583, doi:10.3762/bjoc.15.53

• , geodiamolides and seragamides, is reported. The key step is a Negishi cross coupling of (R)-(3-methoxy-2-methyl-3-oxopropyl)zinc(II) bromide and an (E)-iodoalkene that was synthesized via an aluminium ester enolate attack at (R)-propylene oxide. The overall synthesis comprises nine steps with an overall yield

• )-propylene oxide. The C4–C5 double bond would be formed by Corey–Fuchs reaction. Reaction of the aluminium enolate of tert-butyl propionate (9, Scheme 2) with (S)-propylene oxide had provided Taylor et al. with a mixture of diastereomers of α-methylated γ-hydroxyester 11 favouring the (2S,4S)-syn over the

• (2R,4S)-anti isomer [35][36]. As the configuration at C4 was expected to be invertible in a later step, we aimed for the (2R,4R) configuration by choosing (R)-propylene oxide as electrophile. We obtained an acceptable ratio of diastereomers of 11 (84:16 in favour of (2R,4R), 62% combined) after having

Copolymerization of epoxides with cyclic anhydrides catalyzed by dinuclear cobalt complexes

• Yo Hiranoi and
• Koji Nakano

Beilstein J. Org. Chem. 2018, 14, 2779–2788, doi:10.3762/bjoc.14.255

• benzene ring as a linker and their activities in copolymerization reactions. The dinuclear cobalt complexes showed a higher catalytic activity for the copolymerization of propylene oxide with phthalic anhydride than the corresponding mononuclear cobalt–salen complex and achieved one of the highest

• compared to the corresponding mononuclear cobalt–salen complexes [40]. During the course of our study, the dinuclear cobalt–salen complex (R,R,S,S)-1 was found to exhibit a high catalytic activity for the alternating copolymerization of propylene oxide (PO) with phthalic anhydride (PA, Figure 1). The

• )-8 and (R,R,R,R)-8 were then treated with cobalt(II) nitrate and the following oxidation under air afforded the corresponding dinuclear cobalt–salen complexes (R,R,S,S)-2 and (R,R,R,R)-2, respectively. Copolymerization of propylene oxide with phthalic anhydride The catalysts’ performances were

Phosphonic acid: preparation and applications

• Charlotte M. Sevrain,
• Mathieu Berchel,
• Hélène Couthon and
• Paul-Alain Jaffrès

Beilstein J. Org. Chem. 2017, 13, 2186–2213, doi:10.3762/bjoc.13.219

• was also reported [139][140]. It must be noted that the reaction work-up is usually slightly different since the treatment with propylene oxide that acts as an acid scavenger, can be applied during the purification step. The preparation of phosphonic acid from diphenyl phosphonate was reported to

The chemistry and biology of mycolactones

• Matthias Gehringer and
• Karl-Heinz Altmann

Beilstein J. Org. Chem. 2017, 13, 1596–1660, doi:10.3762/bjoc.13.159

One-pot synthesis of block-copolyrotaxanes through controlled rotaxa-polymerization

• Jessica Hilschmann,
• Gerhard Wenz and
• Gergely Kali

Beilstein J. Org. Chem. 2017, 13, 1310–1315, doi:10.3762/bjoc.13.127

• ]. There are several CD-based polyrotaxanes known with homo- and block-copolymer axes, mostly based on poly(ethylene oxide), poly(propylene oxide) or their copolymers [15][16][17][18][19][20][21], since these polymers can form sufficiently stable complexes with CDs. The application potential of these

Identification, synthesis and mass spectrometry of a macrolide from the African reed frog Hyperolius cinnamomeoventris

• Markus Menke,
• Pardha Saradhi Peram,
• Iris Starnberger,
• Walter Hödl,
• Gregory F.M. Jongsma,
• David C. Blackburn,
• Mark-Oliver Rödel,
• Miguel Vences and
• Stefan Schulz

Beilstein J. Org. Chem. 2016, 12, 2731–2738, doi:10.3762/bjoc.12.269

• )-configured double bond, although in moderate yield (see Supporting Information File 1 for full experimental data). A similar synthetic strategy was applied for the synthesis of macrolide 1 (Scheme 2). The stereogenic center was introduced using commercially available (R)-propylene oxide (13) as starting

• natural compound, the other enantiomer (S)-1 was needed as well. It was synthesized according to the synthesis shown in Scheme 2, starting from (S)-propylene oxide instead of the (R)-enantiomer 13. The stereochemistry was determined by chiral gas chromatography as shown in Figure 4. The coinjection of

• -olide ((R)-1). The enantiomer was obtained in a similar sequence, starting from (S)-propylene oxide instead of 13. Supporting Information Supporting Information File 474: Experimental procedures, mass spectra of macrolides, alternative fragmentation pathway, enantiomer separation by GC–MS, 1H and 13C

Rearrangements of organic peroxides and related processes

• Ivan A. Yaremenko,
• Vera A. Vil’,
• Dmitry V. Demchuk and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162

• rearrangements and related processes play an important role in the chemistry of oxidation processes. Thus, the key reagent in the Sharpless epoxidation of allylic alcohols [48] and in the manufacture of propylene oxide via the Prilezhaev reaction [49][50][51] is tert-butyl hydroperoxide. In industry, phenol and

Multicomponent reactions: A simple and efficient route to heterocyclic phosphonates

• Mohammad Haji

Beilstein J. Org. Chem. 2016, 12, 1269–1301, doi:10.3762/bjoc.12.121

• -oxazolopiperidines 52 with 58% yield and 79:21 dr. Further reduction and hydrogenolysis of 52 in the presence of Pd/C led to aminoester 53 which was converted to (S)-piperidin-2-phosphonic acid (54) through acidic hydrolysis and subsequent treatment with propylene oxide in 42% overall yield and 58% ee (Scheme 13

Synthesis of constrained analogues of tryptophan

• Elisabetta Rossi,
• Valentina Pirovano,
• Marco Negrato,
• Giorgio Abbiati and
• Monica Dell’Acqua

Beilstein J. Org. Chem. 2015, 11, 1997–2006, doi:10.3762/bjoc.11.216

• hydrochloric acid (12 N) in a multimode microwave oven at 120 °C for 2 h, then with an excess of propylene oxide in ethanol at reflux for 1 h, and finally purified by flash chromatography. The whole reaction sequence was realized in a one-flask procedure. The obtained compounds 6a–e and the relative reaction

Robust bifunctional aluminium–salen catalysts for the preparation of cyclic carbonates from carbon dioxide and epoxides

• Yuri A. Rulev,
• Zalina Gugkaeva,
• Victor I. Maleev,
• Michael North and
• Yuri N. Belokon

Beilstein J. Org. Chem. 2015, 11, 1614–1623, doi:10.3762/bjoc.11.176

• reported in Table 2, cyclic carbonate, catalyst and unreacted epoxide (for entries 10 and 11) were the only species detected by 1H NMR spectroscopy of the crude reaction product prior to purification by column chromatography. The moderate yield for propylene oxide (Table 2, entry 6) can be explained by

Surprisingly facile CO₂ insertion into cobalt alkoxide bonds: A theoretical investigation

• Willem K. Offermans,
• Claudia Bizzarri,
• Walter Leitner and
• Thomas E. Müller

Beilstein J. Org. Chem. 2015, 11, 1340–1351, doi:10.3762/bjoc.11.144

• cyclic carbonates Cyclic carbonates can be formed either by a backbiting mechanism from a growing polymer chain [30] (Scheme 4) or directly by the catalytic cycloaddition of CO2 and epoxides [27][28][29]. Sun and Zhang modelled the cycloaddition of CO2 with propylene oxide, catalysed by

• alkylmethylimidazolium chlorine ionic liquids [37]. They identified competitive three-step and two-step pathways, both having the ring opening of propylene oxide as the rate-determining step. In the three-step pathway, the ring opening precedes the CO2 insertion. By contrast, in the two-step pathway, the ring opening

• to be facilitated considerably by hydrogen bonding interactions. Thus, a scaffold of hydrogen bonds can compensate for the lack of a Lewis acid metal center to activate the CO2 molecule. In addition, Zhang et al. investigated the coupling of propylene oxide with CO2 catalysed by a copper(I

Chemoselective O-acylation of hydroxyamino acids and amino alcohols under acidic reaction conditions: History, scope and applications

• Tor E. Kristensen

Beilstein J. Org. Chem. 2015, 11, 446–468, doi:10.3762/bjoc.11.51

• propylene oxide in lower alcohols [46]. The acrylic derivatives, however, must be kept in salt form to avoid decomposition by conjugate addition. Acylation of hydroxyproline with aliphatic acyl chlorides in CF3CO2H gave a near quantitative yield of product (although the total yield was eroded by the

• acid chloride with SOCl2. The acid chloride was subsequently used directly in acidic O-acylation reactions of hydroxyproline, serine and threonine in CF3CO2H at gram-scale. The product hydrochlorides were converted to free amino acids with propylene oxide in EtOH. Optionally, the ketone functionality

Anion effect controlling the selectivity in the zinc-catalysed copolymerisation of CO₂ and cyclohexene oxide

• Sait Elmas,
• Muhammad Afzal Subhani,
• Walter Leitner and
• Thomas E. Müller

Beilstein J. Org. Chem. 2015, 11, 42–49, doi:10.3762/bjoc.11.7

• ) [21][22][23][24] atom (Type II). Most catalysts based on Salen-type ligands are substrate specific and are most efficient for the copolymerisation of CO2 with propylene oxide (PO). The use of zinc-based catalysts of Type I appears more favourable from an environmental perspective compared to the use

A carbohydrate approach for the formal total synthesis of (−)-aspergillide C

• Pabbaraja Srihari,
• Namballa Hari Krishna,
• Ydhyam Sridhar and
• Ahmed Kamal

Beilstein J. Org. Chem. 2014, 10, 3122–3126, doi:10.3762/bjoc.10.329

• reaction followed by the reduction of the triple bond to the trans double bond. Alkyne 7 can be synthesized from alkyne 8 involving an isomerization reaction. Alkyne 8 was easily accessible from (R)-propylene oxide (9) through an epoxide opening reaction with 1-butyne. Results and Discussion In recent work

• on aspergillides, Achmatowicz adducts were utilized as the key source for the construction of the dihydropyran moiety and the side arm was synthesized using a Zipper rearrangement as a key reaction after an epoxide ring opening reaction of (R)-propylene oxide/(S)-propylene oxide with n-BuLi. In the

• amounts starting from (R)-propylene oxide (9) as shown in Scheme 2. We proceeded further by utilizing it for masking the functionalities. Compound 10 was disilylated using TMSCl in the presence of n-BuLi and later treated with 1 N HCl to get the free secondary alcohol which was further treated with

First chemoenzymatic stereodivergent synthesis of both enantiomers of promethazine and ethopropazine

• Paweł Borowiecki,
• Daniel Paprocki and
• Maciej Dranka

Beilstein J. Org. Chem. 2014, 10, 3038–3055, doi:10.3762/bjoc.10.322

• -phenothiazin-10-yl)propan-2-ol (±)-3 was synthesized according to the method described by Clement et al. [59], in which propylene oxide (2) was regioselectively opened by phenothiazine (1) in the presence of n-butyllithium (n-BuLi) at ambient temperature providing desired alcohol (±)-3 in 64–77% yield

• suggests that this particular process is most probably inaccessible through the sodium salt of phenothiazine (1) due to multiple substitution at aromatic ring carbon atoms and some other byproducts of the non-regioselective propylene oxide ring opening. With the hope of eliminating the unwanted side

• [tetrabutylammonium bromide (TBAB) or tetrabutylammonium hydrogensulfate (TBAHS)], the epoxide 2 ring opening proceeded unsuccessfully. Again, the amount of the formed impurities was too large to isolate pure fraction. This provoked us to change the synthetic strategy by excluding at first propylene oxide (2) as the

Synthesis of modified cyclic and acyclic dextrins and comparison of their complexation ability

• Kata Tuza,
• László Jicsinszky,
• Tamás Sohajda,
• István Puskás and
• Éva Fenyvesi

Beilstein J. Org. Chem. 2014, 10, 2836–2843, doi:10.3762/bjoc.10.301

• treated with strong cation ion exchanger. The products were obtained by evaporation. Yield: 1.4/1.5/1.7 g (80–85%). 1-O-Benzyl-HP (DS~4)-maltooligomers: 1-O-Benzyl-G6, G7 and G8 maltooligomers (0.25 mmol) were dissolved in aqueous solutions of NaOH (2.5/1.2/1.2 mmol; 1/0.5/0.5 mL water), 1,2-propylene

• oxide (1.6 mmol) was added and the solutions were stirred at 5 °C for 24 h. As the TLC showed no further changes, the reaction mixtures were treated with strong ion exchanger, and then evaporated to dryness. The products were isolated by precipitation in acetone from aqueous solutions. Yield: 0.22/0.24