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

Copolymerization and terpolymerization of carbon dioxide/propylene oxide/phthalic anhydride using a (salen)Co(III) complex tethering four quaternary ammonium salts

• Jong Yeob Jeon,
• Seong Chan Eo,
• Jobi Kodiyan Varghese and
• Bun Yeoul Lee

Beilstein J. Org. Chem. 2014, 10, 1787–1795, doi:10.3762/bjoc.10.187

• /epoxide copolymerizations, shows high activity for propylene oxide/phthalic anhydride (PO/PA) copolymerizations and PO/CO2/PA terpolymerizations. In the PO/PA copolymerizations, full conversion of PA was achieved within 5 h, and strictly alternating copolymers of poly(1,2-propylene phthalate)s were

• -transition temperature (48 °C) than the CO2/PO alternating copolymer (40 °C). Keywords: carbon dioxide; CO2 chemistry; cobalt complex; phthalic anhydride; propylene oxide; terpolymerization; Introduction Carbon dioxide (CO2) can be utilized to prepare aliphatic polycarbonates through coupling reactions

Continuous flow photocyclization of stilbenes – scalable synthesis of functionalized phenanthrenes and helicenes

• Quentin Lefebvre,
• Marc Jentsch and
• Magnus Rueping

Beilstein J. Org. Chem. 2013, 9, 1883–1890, doi:10.3762/bjoc.9.221

• corresponding dihydrophenanthene is subsequently oxidized with iodine to give the desired phenanthrene and HI, which can be quenched by propylene oxide or THF. Results and Discussion In order to accomplish a first general photocyclization we started with the photocyclization of stilbene. Optimization of the

• reaction conditions in a small flow setup (5 mL FEP tubing, 150 W UV-lamp) is presented in Table 1. Although both THF and propylene oxide showed good ability to quench HI, we choose THF as additive due to its lower cost, volatility and toxicity [23][24]. Under the optimized conditions, E-stilbene (1a

Metal-free aerobic oxidations mediated by N-hydroxyphthalimide. A concise review

• Lucio Melone and
• Carlo Punta

Beilstein J. Org. Chem. 2013, 9, 1296–1310, doi:10.3762/bjoc.9.146

• peroxyl radical generated in situ is the real epoxidizing agent (Scheme 20). This protocol was successfully applied on a larger scale (1 liter Büchi glass vessel) for the synthesis of propylene oxide from the corresponding propene [56], and more recently under continuous-flow conditions, by means of a new

Chemoenzymatic synthesis and biological evaluation of enantiomerically enriched 1-(β-hydroxypropyl)imidazolium- and triazolium-based ionic liquids

• Paweł Borowiecki,
• Małgorzata Milner-Krawczyk and
• Jan Plenkiewicz

Beilstein J. Org. Chem. 2013, 9, 516–525, doi:10.3762/bjoc.9.56

• -propylene oxide with imidazole or 1,2,4-triazole. Lipase-catalyzed transesterification of alcohols with vinyl acetate resulted in kinetic enantiomers resolution. Separated (S)-enantiomers of (+)-1-(1H-imidazol-1-yl)propan-2-ol and (+)-1-(1H-1,2,4-triazol-1-yl)propan-2-ol were quaternized with alkyl bromides

• optically active ILs. Reagents and conditions: (i) 1,2-propylene oxide (1.1 equiv), 32 °C, 24 h; (ii) vinyl acetate (5 equiv), Novozyme SP 435, 2-methyl-2-butanol, rt, 48 h, magnetic stirrer; (iii) vinyl acetate (5 equiv), enzyme, 2-methyl-2-butanol/MTBE (methyl tert-butyl ether), rt, 250 rpm; (iv) RX (3

• ). Next, these compounds were used as a new type of substrate in lipase-catalyzed transesterification, yielding both enantiomers with good optical purity. The syntheses of the secondary alcohols (±)-3a and (±)-3b were accomplished by the addition of imidazole (2a) or 1,2,4-triazole (2b) to 1,2-propylene

Restructuring polymers via nanoconfinement and subsequent release

• Alan E. Tonelli

Beilstein J. Org. Chem. 2012, 8, 1318–1332, doi:10.3762/bjoc.8.151

• -nucleated PET not only possesses improved properties, but contains no incompatible additives, and so may be readily recycled. Coalesced block copolymers The triblock copolymer PCL-PPG-PCL, with noncrystallizable central poly(propylene oxide blocks), was synthesized by coordinated ring-opening polymerization

On the proposed structures and stereocontrolled synthesis of the cephalosporolides

• Sami F. Tlais and
• Gregory B. Dudley

Beilstein J. Org. Chem. 2012, 8, 1287–1292, doi:10.3762/bjoc.8.146

• silyl ether 19 with the (R)-propylene oxide produced the internal alkyne 20 (Scheme 5). Gold(I) chloride in MeOH induced the spiroketalization of alkyne 20 with concomitant cleavage of the PMP acetal and partial cleavage of the TBS ether. After completion of the desilylation with TBAF, a mixture of 5,5

Mutational analysis of a phenazine biosynthetic gene cluster in Streptomyces anulatus 9663

• Orwah Saleh,
• Katrin Flinspach,
• Lucia Westrich,
• Andreas Kulik,
• Bertolt Gust,
• Hans-Peter Fiedler and
• Lutz Heide

Beilstein J. Org. Chem. 2012, 8, 501–513, doi:10.3762/bjoc.8.57

• used to inoculate individual wells of the deep-well plates, with each well containing 3 mL medium. In initial experiments, the medium was supplemented with 0.6% (w/v) of the siloxylated ethylene oxide/propylene oxide copolymer Q2-5247 (Dow Corning, USA), which acts as an oxygen carrier and has been

Asymmetric synthesis of quaternary aryl amino acid derivatives via a three-component aryne coupling reaction

• Elizabeth P. Jones,
• Peter Jones,
• Andrew J. P. White and
• Anthony G. M. Barrett

Beilstein J. Org. Chem. 2011, 7, 1570–1576, doi:10.3762/bjoc.7.185

• equatorial position, as there is now a 1,2-gauche interaction with the bulky di-methoxyaryl group adjacent to it. We consider that neither of these transition states is lower in energy, which would be consistent with the lack of diastereoselectivity. Finally, the addition of (R)-propylene oxide as the

• electrophile in the presence of boron trifluoride etherate (Table 1, entry 10) gave alcohol 6j. When (S)-propylene oxide was used instead there was no reaction, and indeed Schöllkopf noted significant levels of kinetic resolution when such reactions were performed with racemic oxiranes [23]. In our previous

A gold-catalyzed alkyne-diol cycloisomerization for the synthesis of oxygenated 5,5-spiroketals

• Sami F. Tlais and
• Gregory B. Dudley

Beilstein J. Org. Chem. 2011, 7, 570–577, doi:10.3762/bjoc.7.66

• pantolactone (11, Scheme 5) [37]. An alkyne zipper reaction, protection, and coupling with propylene oxide gave homopropargyl 13. Cycloisomerization of 13 to the spiroketal (14) was investigated under a variety of conditions, some of which are featured in Table 1. Utimoto’s general conditions as reported

Kinetics and mechanism of vanadium catalysed asymmetric cyanohydrin synthesis in propylene carbonate

• Michael North and
• Marta Omedes-Pujol

Beilstein J. Org. Chem. 2010, 6, 1043–1055, doi:10.3762/bjoc.6.119

• prepared by a 100% atom economical reaction between epoxides and CO2 (Scheme 2) [65]. The green credentials of propylene carbonate are enhanced by the commercialization of a low temperature synthesis of propylene oxide from propene and hydrogen peroxide [66][67][68][69][70], by the development of a greener

• synthesis of hydrogen peroxide [71], and by the combination of these processes into a one-pot synthesis of propylene oxide from propene, hydrogen and oxygen [72][73]. In addition, it has been shown that in the presence of an appropriate catalyst, the reaction between epoxides and carbon dioxide can be

Recent progress on the total synthesis of acetogenins from Annonaceae

• Nianguang Li,
• Zhihao Shi,
• Yuping Tang,
• Jianwei Chen and
• Xiang Li

Beilstein J. Org. Chem. 2008, 4, No. 48, doi:10.3762/bjoc.4.48