Photocycloaddition of aromatic and aliphatic aldehydes to isoxazoles: Cycloaddition reactivity and stability studies

• Axel G. Griesbeck,
• Marco Franke,
• Jörg Neudörfl and
• Hidehiro Kotaka

Beilstein J. Org. Chem. 2011, 7, 127–134, doi:10.3762/bjoc.7.18

• -controlled formation of the corresponding triplet 1,4-biradical and high stereocontrol due to SOC-controlled crossing from the triplet to the singlet surface [4][5]. Reaction behavior of the photoproducts 9a–c All bicyclic oxetanes obtained in the analytical photochemical experiments as well as in

Highly substituted benzannulated cyclooctanol derivatives by samarium diiodide-induced cyclizations

• Jakub Saadi,
• Irene Brüdgam and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2010, 6, 1229–1245, doi:10.3762/bjoc.6.141

• cyclooctanol derivatives with a high degree of regio- and stereocontrol. Experimental General: All reactions were carried out under argon in flame-dried flasks, and the components were added by syringe. All solvents were dried by standard methods. Thin layer chromatography (TLC) was carried out on commercial

Synthesis of a new class of aminocyclitol analogues with the conduramine D-2 configuration

• Latif Kelebekli,
• Yunus Kara and
• Murat Celik

Beilstein J. Org. Chem. 2010, 6, No. 15, doi:10.3762/bjoc.6.15

• the bicyclo[4.2.0]octane frame work, with stereocontrol during the formation of all the stereogenic centres. Experimental Melting points were determined on a Büchi 539 capillary melting apparatus and are uncorrected. Infrared spectra were obtained from KBr or film on a Mattson 1000 FT-IR

Diastereoselective functionalisation of benzo-annulated bicyclic sultams: Application for the synthesis of cis-2,4-diarylpyrrolidines

• Susan Kelleher,
• Pierre-Yves Quesne and
• Paul Evans

Beilstein J. Org. Chem. 2009, 5, No. 69, doi:10.3762/bjoc.5.69

• complete stereocontrol (de >95%). The stereochemical outcome was confirmed by single-crystal X-ray crystallography (Figure 1, and see crystallographic data). The use of in situ generated trifluoromethyl-methyldioxirane was also investigated and in the case of 5a, very efficient formation of 7a was observed

Polyionic polymers – heterogeneous media for metal nanoparticles as catalyst in Suzuki–Miyaura and Heck–Mizoroki reactions under flow conditions

• Klaas Mennecke and
• Andreas Kirschning

Beilstein J. Org. Chem. 2009, 5, No. 21, doi:10.3762/bjoc.5.21

• with 4′-bromoacetophenone coupling with styrene yielded Heck-product 30 in only 35%. In order to generalize the reaction protocol different aryl iodides were coupled with styrene. In all cases, the C-C coupling products were formed within 0.5 to 24 h in very good yield with excellent stereocontrol (see

Asymmetric synthesis of biaryl atropisomers by dynamic resolution on condensation of biaryl aldehydes with (−)-ephedrine or a proline- derived diamine

• Ann Bracegirdle,
• Jonathan Clayden and
• Lai Wah Lai

Beilstein J. Org. Chem. 2008, 4, No. 47, doi:10.3762/bjoc.4.47

• substrates Previous success with stereocontrol employing ephedrine-derived oxazolidines [15][26][27][34][35] and proline-derived imidazolidines [25][27] prompted us to investigate the thermal stability and conformational preferences of similar products arising from condensation reactions of 2-formylbiaryls

Mechanistic aspects of the isomerization of Z-vinylic tellurides double bonds in the synthesis of potassium Z-vinyltrifluoroborate salts

• Hélio A. Stefani,
• Rafael C. Guadagnin,
• Artur F. Keppler,
• Giancarlo V. Botteselle,
• João V. Comasseto and
• Carlos A. Suganuma

Beilstein J. Org. Chem. 2008, 4, No. 9, doi:10.1186/1860-5397-4-9

• organometallic species obtained in this way can also react with carbonyl compounds, α,β-unsaturated systems, or epoxides [9][10][11] with complete retention of the double-bond stereochemistry. Taking advantage of the regio- and stereocontrol of the preparation of Z-vinylic tellurides [12], and of the unique

Analogues of amphibian alkaloids: total synthesis of (5R,8S,8aS)-(−)-8-methyl- 5-pentyloctahydroindolizine (8-epi-indolizidine 209B) and [(1S,4R,9aS)-(−)-4-pentyloctahydro- 2H-quinolizin- 1-yl]methanol

• Joseph P. Michael,
• Claudia Accone,
• Charles B. de Koning and
• Christiaan W. van der Westhuyzen

Beilstein J. Org. Chem. 2008, 4, No. 5, doi:10.1186/1860-5397-4-5

• indolizidine alkaloids [19]. Results and Discussion Steps in our reported total synthesis of (−)-indolizidine (−)-209B 8 [13] are shown in Scheme 1. Absolute stereocontrol resulted from use of the Davies protocol [20][21], whereby the homochiral amine (+)-14 prepared from tert-butyl (E)-oct-2-enoate and (R)-N

The enantiospecific synthesis of (+)-monomorine I using a 5-endo- trig cyclisation strategy

• Malcolm B. Berry,
• Donald Craig,
• Philip S. Jones and
• Gareth J. Rowlands

Beilstein J. Org. Chem. 2007, 3, No. 39, doi:10.1186/1860-5397-3-39

• enables two C-C bond forming steps, allows stereocontrol of the alkene and activates the alkene to cyclisation. Furthermore, the sulfone can be used to elaborate the basic framework post-cyclisation. In this publication we outline the application of this methodology to the synthesis of the indolizidine

Single and double stereoselective fluorination of (E)-allylsilanes

• Marcin Sawicki,
• Angela Kwok,
• Matthew Tredwell and
• Véronique Gouverneur

Beilstein J. Org. Chem. 2007, 3, No. 34, doi:10.1186/1860-5397-3-34

• these substrates suffered from a poor level of diastereocontrol, thereby limiting the synthetic value of these reactions.[16][17] The absence of a silylated stereogenic centre is likely to be responsible for the poor stereocontrol observed upon fluorination of these substrates. We envisaged that the

• crude mixture and its structure was tentatively assigned as syn (Z)-2e (entry 1). The benzyl-substituted allylsilane anti-1f was fluorinated in 90% yield with a similar sense and level of stereocontrol (entry 2). Excellent transfer of chirality was also observed for the fluorination of anti (E)-1g

• demanding and required higher temperature to reach completion. Under these conditions, the level of stereocontrol of the second fluorination was moderate (Scheme 3). To unambiguously confirm the stereochemistry of syn (E)-3 [major diastereomer], this compound was converted into the known symmetrical

Allylsilanes in the synthesis of three to seven membered rings: the silylcuprate strategy

• Asunción Barbero,
• Francisco J. Pulido and
• M. Carmen Sañudo

Beilstein J. Org. Chem. 2007, 3, No. 16, doi:10.1186/1860-5397-3-16

• under Lewis acid catalysis. [10] Thus, silicon assisted cyclization of oxoallylsilanes 3–8 in the presence of TiCl4 or EtAlCl2 results in the formation of 3-methylene-1-cyclopentanols 11–14 with a high degree of stereocontrol (Scheme 3). [7] The cis stereochemistry observed in 11 might indicate a

• -cyclopropane moiety, from open chain allylsilanes in just one step. The high stereocontrol associated to the ring formation allows the synthesis of enantiomerically pure spiro-tricyclic alcohols containing an angular OH-group, such as 38 (Scheme 7). [20] The use of reagents different from organoaluminun

Pd-catalysed [3 + 3] annelations in the stereoselective synthesis of indolizidines

• Olivier Y. Provoost,
• Andrew J. Hazelwood and
• Joseph P. A. Harrity

Beilstein J. Org. Chem. 2007, 3, No. 8, doi:10.1186/1860-5397-3-8

• [3 + 3] annelation of enantiomerically pure aziridine 7 provides the functionalised piperidine 8 that can be elaborated to the indolizidine skeleton in only 4 steps with good stereocontrol. Introduction Indolizidine alkaloids represent one of the most structurally diverse classes of natural products

Contemporary organosilicon chemistry

• Steve Marsden

Beilstein J. Org. Chem. 2007, 3, No. 4, doi:10.1186/1860-5397-3-4

• Chemistry". We have contributions from some of the leading practitioners in the area, covering a wide range of topics including the stereoselective construction of oxygen and nitrogen-containing heterocycles, the use of tethered silicon reagents to deliver acyclic stereocontrol, chiral-at-silicon reagents

Reagent controlled addition of chiral sulfur ylides to chiral aldehydes

• Varinder K. Aggarwal and
• Jie Bi

Beilstein J. Org. Chem. 2005, 1, No. 4, doi:10.1186/1860-5397-1-4

• reversibility in betaine formation, which impacted on the stereocontrol at the C2 position. Introduction The reaction of chiral sulfur ylides with carbonyl compounds, operating in either a catalytic or stoichiometric mode, have emerged as a useful and powerful method in the arsenal of asymmetric

• betaine (high reversibility results in low stereocontrol) whilst the C2 stereochemistry is controlled by the degree of reversibility in syn betaine formation (high reversibility leads to high diastereocontrol in favor of the trans epoxide).[2] We questioned whether the high level of reagent control