Carbamate-directed benzylic lithiation for the diastereo- and enantioselective synthesis of diaryl ether atropisomers

• Abigail Page and
• Jonathan Clayden

Beilstein J. Org. Chem. 2011, 7, 1327–1333, doi:10.3762/bjoc.7.156

• higher when (−)-sparteine was present (though this may also be due to an improvement in the stereospecificity of the quench). Fourthly, diastereoselectivity, unlike enantioselectivity, varies significantly according to the electrophile employed, showing that the product d.r. is determined in the

• the metallation/quench of 11. Variation of yield and selectivity with quench time. Stereospecificity in the tin–lithium exchange/quench reactions. Supporting Information Supporting Information File 300: Experimental details and spectral data. Acknowledgements We are grateful to GSK and the EPSRC for

Alkene selenenylation: A comprehensive analysis of relative reactivities, stereochemistry and asymmetric induction, and their comparisons with sulfenylation

• Vadim A. Soloshonok and
• Donna J. Nelson

Beilstein J. Org. Chem. 2011, 7, 744–758, doi:10.3762/bjoc.7.85

• anti stereospecificity [58][59]. The nucleophile attacks the more substituted carbon in the seleniranium ion (Scheme 1), unless that carbon bears bulky groups, such as tert-butyl or cyclohexyl [55][56] or unless the open carbocation is stabilized, e.g., by an aryl group or a heteroatom [60][61][62][63

When cyclopropenes meet gold catalysts

• Frédéric Miege,
• Christophe Meyer and
• Janine Cossy

Beilstein J. Org. Chem. 2011, 7, 717–734, doi:10.3762/bjoc.7.82

• 62a–62f. Excellent results were obtained with allylic ethers bearing one (62a, 62b) or two substituents (62c–62e) at the terminal position of the olefin and the corresponding oxabicyclic compounds were isolated in high yields (93–99%). The stereospecificity of the cyclopropanation process was

Intraannular photoreactions in pseudo-geminally substituted [2.2]paracyclophanes

• Henning Hopf,
• Vitaly Raev and
• Peter G. Jones

Beilstein J. Org. Chem. 2011, 7, 658–667, doi:10.3762/bjoc.7.78

• removable spacer can be developed considerably further for the stereospecific synthesis of many other compounds. Results and Discussion However, the detailed stereochemical situation is in fact more complex, and the origin of the stereospecificity requires a more thorough analysis. For example, we have

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

• . The use of α,α-dialkyl hydroxy esters 8 is more successful: Thioethers 10 are formed in high yield and with almost complete stereospecificity (Scheme 3). Using the same principles of low steric bulk and electronic inhibition of the SN1 reaction pathway, α-(sulfonyloxy)nitriles, easily prepared from

• with BtzSH (36) and BoxSH (37). The reaction proceeds well with many hindered substrates incorporating aromatic, alkyl and ester substituents with excellent stereospecificity. Enantiomerically pure thiols can also be made from the product: Aromatic thioether 38 is reduced with lithium aluminium hydride