Enantioselective Michael addition of 2-hydroxy-1,4-naphthoquinones to nitroalkenes catalyzed by binaphthyl-derived organocatalysts

• Saet Byeol Woo and
• Dae Young Kim

Beilstein J. Org. Chem. 2012, 8, 699–704, doi:10.3762/bjoc.8.78

• synthesis [12], and intensive research efforts have been directed toward the development of enantioselective catalytic protocols for this reaction [13][14][15]. The organocatalyst-mediated enantioselective conjugate addition reactions, which are both powerful and environmentally friendly, have been

• (97% ee, Table 2, entry 11). In conclusion, we have developed a highly efficient catalytic, enantioselective Michael addition of 2-hydroxy-1,4-naphthoquinone to nitroalkenes using a binaphthyl-derived tertiary amine-thiourea organocatalyst. The various types of nitroalkylated naphthoquinone

Facile isomerization of silyl enol ethers catalyzed by triflic imide and its application to one-pot isomerization–(2 + 2) cycloaddition

• Kazato Inanaga,
• Yu Ogawa,
• Yuuki Nagamoto,
• Akihiro Daigaku,
• Hidetoshi Tokuyama,
• Yoshiji Takemoto and
• Kiyosei Takasu

Beilstein J. Org. Chem. 2012, 8, 658–661, doi:10.3762/bjoc.8.73

• procedure would be required. In this communication, we describe isomerization of silyl enol ethers by an organocatalyst under mild conditions and its application to a one-pot catalytic reaction involving isomerization of silyl enol ethers and (2 + 2) cycloaddition. Results and Discussion During our research

Recent advances in the gold-catalyzed additions to C–C multiple bonds

• He Huang,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2011, 7, 897–936, doi:10.3762/bjoc.7.103

• malononitriles 375 and N-Boc-protected imines 374 (Scheme 60) [176]. In the alkyne hydroamination (which is based on a bifunctional organocatalytic Mannich-type reaction, subsequent gold-catalyzed alkyne hydroamination and isomerization) thiourea-based hydrogen bonding organocatalyst 373 and PPh3AuNTf2 proved to

Asymmetric synthesis of tertiary thiols and thioethers

• Jonathan Clayden and
• Paul MacLellan

Beilstein J. Org. Chem. 2011, 7, 582–595, doi:10.3762/bjoc.7.68

• of the enantiomers of hindered enone 46 by addition, oxidation and elimination of a sulfenic acid under basic conditions (Scheme 18) [45]. Xiao and co-workers developed an organocatalytic process for the addition of thiols to nitroalkenes [46]. Using thiourea organocatalyst 48, conjugate addition of

Application of the diastereoselective photodeconjugation of α,β-unsaturated esters to the synthesis of gymnastatin H

• Ludovic Raffier and
• Olivier Piva

Beilstein J. Org. Chem. 2011, 7, 151–155, doi:10.3762/bjoc.7.21

• ]. In this context, we have considered an alternative synthetic route to the fatty acid common to all gymnastatins according to a photoisomerisation–diastereoselective protonation sequence involving catalytic amounts of an achiral organocatalyst (e.g., amino alcohol 4b). Our goal was to describe the

The C–F bond as a conformational tool in organic and biological chemistry

• Luke Hunter

Beilstein J. Org. Chem. 2010, 6, No. 38, doi:10.3762/bjoc.6.38

• consequently attacks from the bottom (si) face, leading to epoxide 38 with high enantioselectivity. In a control experiment, the related organocatalyst 2-(diphenylmethyl)pyrrolidine (containing a hydrogen atom instead of the fluorine atom of 35) also catalyses the same reaction but with lower

• enantioselectivity suggesting that the fluorine atom of 35 helps to rigidify the activated intermediate and thereby enhances selectivity. Another fluorinated organocatalyst has recently featured in the first example of an asymmetric transannular aldol reaction (Figure 10) [35]. (S)-proline (39) is able to catalyse

Asymmetric reactions in continuous flow

• Xiao Yin Mak,
• Paola Laurino and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2009, 5, No. 19, doi:10.3762/bjoc.5.19

• temperatures than previously reported in batch, resulting in shorter reaction times and lower loadings of the organocatalyst 7 (Scheme 3). Slightly higher yields and selectivities, compared to reactions in both batch and in the microwave were obtained. This study was extended to an example using cyclohexanone

Ru-catalyzed dehydrogenative coupling of carboxylic acids and silanes - a new method for the preparation of silyl ester

• Guo-Bin Liu and
• Hong-Yun Zhao

Beilstein J. Org. Chem. 2008, 4, No. 27, doi:10.3762/bjoc.4.27

• )3Cl [46] and promoted by organocatalyst such as triphenylphosphine [47]. Generally, catalysts such as transition metals are expensive. [CuH(Ph3P)] requires a multiple-step synthetic approach and in-situ generation protocols. Results and Discussion In this communication, we wish to report the first

Towards practical biocatalytic Baeyer- Villiger reactions: applying a thermostable enzyme in the gram- scale synthesis of optically- active lactones in a two-liquid- phase system

• Frank Schulz,
• François Leca,
• Frank Hollmann and
• Manfred T. Reetz

Beilstein J. Org. Chem. 2005, 1, No. 10, doi:10.1186/1860-5397-1-10

• . We compared the system developed in this study to an analogous synthetic organocatalyst for the enantioselective BV-oxidation as described by Murahashi et al. in 2002.[13] The Murahashi system is related to PAMO because it also uses a flavin-derived catalyst within a chiral environment. Of course

• . Comparison of P3-PAMO with Murahashi's chiral bisflavin organocatalyst as a chemical model catalyst for enantioselective BV-oxidations. Supporting Information Supporting Information File 12: Experimental section. Acknowledgements We gratefully acknowledge a gift of the plasmid pADHB1M1-kan encoding 2°ADH