Synthesis of oxa-bridged derivatives from Diels–Alder bis-adducts of butadiene and 1,2,3,4-tetrahalo-5,5-dimethoxycyclopentadiene

• Faiz Ahmed Khan and
• Karuppasamy Parasuraman

Beilstein J. Org. Chem. 2010, 6, No. 64, doi:10.3762/bjoc.6.64

• treated first with alkaline H2O2 and then with additional NaOH (60 equiv) at 60 °C followed by esterification with diazomethane to obtain the oxa-bridged compound 8 in 42% yield. Bis-diketone 15 was transformed into 10 in 39% yield by a similar method. Unlike the bis-diketones in chloro series (7 and 9

Enantioselective synthesis of tricyclic amino acid derivatives based on a rigid 4-azatricyclo[5.2.1.0^2,6]decane skeleton

• Matthias Breuning,
• Tobias Häuser,
• Christian Mehler,
• Christian Däschlein,
• Carsten Strohmann,
• Andreas Oechsner and
• Holger Braunschweig

Beilstein J. Org. Chem. 2009, 5, No. 81, doi:10.3762/bjoc.5.81

• the racemic ketone rac-9. i) NH4OAc, HOAc, Δ, 4 d, 100%; ii) LiAlH4, THF, Δ, 1 d, 87% [24]; iii) Boc2O, CH2Cl2, rt, 16 h, 85%; iv) NaBH4, Me2SO4, THF, rt, 6 h, then NaOH, H2O2, Δ, 90 min, 75%; v) PCC, Celite®, CH2Cl2, rt, 16 h, 79%. Enantioselective hydrosilylation/oxidation of 11. i) HSiCl3, [Pd(C3H5

• )Cl]2 (0.06 mol %), (R)-MOP (0.25 mol %), toluene, rt, 3 d, then evaporate, then KF, KHCO3, H2O2, THF/MeOH, rt, 1 d, 81%. Initial route to the aldehyde rac-15. i) MePPh3+Br−, t-BuOK, toluene, Δ, 7 h, 77% or Mg, TiCl4, CH2Cl2, 0 °C → rt, 2 h, 55%; ii) NaBH4, Me2SO4, THF, 0 °C → rt, 18 h, then NaOH

• , H2O2, rt, 3 h, 34%; iii) PCC, CH2Cl2, rt, 6 h, 51%; iv) MCPBA, CH2Cl2, rt, 3 h, 60%; v) BF3•OEt2, toluene, 0 °C, 5 min, 35% (rac-17) and 26% (rac-15). Assembly of the amino acid 7a•HCl and the N-tosylamide 7b•HCl. i) MeOCH2PPh3+Cl−, t-BuOK, toluene/THF, rt, 1 d, 84%; ii) Cl3CCO2H, H2O, CH2Cl2, rt, 1.5

2-Phenyl- tetrahydropyrimidine- 4(1H)-ones – cyclic benzaldehyde aminals as precursors for functionalised β²-amino acids

• Markus Nahrwold,
• Arvydas Stončius,
• Anna Penner,
• Beate Neumann,
• Hans-Georg Stammler and
• Norbert Sewald

Beilstein J. Org. Chem. 2009, 5, No. 43, doi:10.3762/bjoc.5.43

• diastereoselectivity being observed for alkylations of 5 compared to alkylations of 2. To release the tert-butyl protected β2-homoaspartate, its precursor 11d was regioselectively degraded in a two step procedure (Scheme 6). Treatment of 11d with LiOH/H2O2 in THF/H2O afforded the ring opening product 15. Although 15

• . DIB, I2, CH2Cl2, rt, 4 h, then BF3·Et2O, rt, 1 h; c) Ni(OAc)2·4H2O/NaBH4, MeOH/THF, 0 °C, 10 min; d) Boc2O, DMAP, CH3CN, 16 h, rt. Diastereoselective alkylation of 5. Selective ring opening of the heterocycle 11d and isolation of orthogonally protected β2-homoaspartate 16. a) LiOH/H2O2, THF/H2O, 0 °C

The development and evaluation of a continuous flow process for the lipase- mediated oxidation of alkenes

• Charlotte Wiles,
• Marcus J. Hammond and
• Paul Watts

Beilstein J. Org. Chem. 2009, 5, No. 27, doi:10.3762/bjoc.5.27

• situ generated peracids derived from formic acid or acetic acid (1)/hydrogen peroxide (2). As H2O2 (2) is itself not sufficiently electrophilic to epoxidise a non-conjugated double bond directly, its use in the formation of a peracid has afforded a route to the epoxidation of alkenes in the presence of

• such as H2O2 (2) and urea–hydrogen peroxide (UHP, 3) [12]. For this transformation, the biocatalysts of choice are lipases (E.C. 3.1.1.3), which are a group of water soluble enzymes that catalyse the hydrolysis of lipid substrates, i.e. triglycerides and fats, in biological systems and are a subclass

• epoxides, with Björkling and co-workers [18][19] initially reporting the generation of epoxides under mild conditions using seven lipases. As Scheme 1 illustrates, the biocatalytic epoxidation involves the lipase catalysed formation of a peroxy acid, from a carboxylic acid and an oxidant, such as H2O2 (2

Oxidative cyclization of alkenols with Oxone using a miniflow reactor

• Yoichi M. A. Yamada,
• Kaoru Torii and
• Yasuhiro Uozumi

Beilstein J. Org. Chem. 2009, 5, No. 18, doi:10.3762/bjoc.5.18

• at 80 °C for 5 min, the cyclization took place very smoothly to afford threo-1-(2-tetrahydrofuranyl)hexan-1-ol (2a) in 99% yield as a single racemic diastereoisomer. Yet when 30% aq H2O2 was used as the oxidant at 80 °C, the cyclization hardly proceeded at all, even with a longer reaction time [32

• ]. We had previously found that a polymeric phosphotungstate catalyst promoted the cyclization of 1a with 30% aq H2O2 at 50 °C with a much longer reaction time (24 h). Thus, Oxone was found to be the most efficient oxidant to promote the cyclization of (Z)-4-decen-1-ol (1a). Although a powerful and

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

Efficient 1,4-addition of α-substituted fluoro(phenylsulfonyl)methane derivatives to α,β-unsaturated compounds

• G. K. Surya Prakash,
• Xiaoming Zhao,
• Sujith Chacko,
• Fang Wang,
• Habiba Vaghoo and
• George A. Olah

Beilstein J. Org. Chem. 2008, 4, No. 17, doi:10.3762/bjoc.4.17

• peroxide [H2O2, 30% (wt)] was attempted in acetic acid at room temperature. Tuning the conditions by using 4-fold excess of H2O2 afforded 90% yield of (nitromethylsulfonyl)benzene overnight (Table 1, entry 1) [26][27][28]. 2a–c and 2e were prepared in 76–91% yields under the optimized condition and used