Radical cascades using enantioenriched 7-azabenzonorbornenes and their applications in synthesis

• David M. Hodgson and
• Leonard H. Winning

Beilstein J. Org. Chem. 2008, 4, No. 38, doi:10.3762/bjoc.4.38

• -observed trend that alkenes bearing less strongly electron-withdrawing substituents were less effective electrophiles in this reaction. Phenyl vinyl sulfone gave trapped rearranged azacycle 13 in 43% yield, with rearranged–reduced azacycle 8 also isolated in 38% yield, suggesting that the rate of

• electrophile trapping with the sulfone corresponds approximately to the rate of hydrogen atom transfer from (TMS)3SiH. Attempted reaction with methyl vinyl ketone, N,N-dimethylacrylamide and methyl propiolate gave rearranged-reduced azacycle 8 in modest yields, as well as small quantities of hydrosilylated

• electrophile (for details see Supporting Information File 1) [26]. Having probed the generality of the reaction, attempts were made to optimise the yields of the electrophile trapping. These studies were performed with phenyl vinyl sulfone, since this had undergone partial electrophile trapping and partial

The role of an aromatic group in remote chiral induction during conjugate addition of α-sulfonylallylic carbanions to ethyl crotonate

• Shlomo Levinger,
• Ranjeet Nair and
• Alfred Hassner

Beilstein J. Org. Chem. 2008, 4, No. 32, doi:10.3762/bjoc.4.32

• -substituted allyl sulfone 1, containing a stereogenic center, proceeded with diastereoselectivity of greater than 8:2 (ratio of 3 to 4), when the Ar substituent in 1 was phenyl or 1-naphthyl (Scheme 1). On the other hand, when this substituent (Ar in Scheme 1) was cyclohexyl, no selectivity at all was

• observed (dr 1:1). We had proposed that π–Li+ interaction may be responsible for this phenomenon. We had shown earlier [2] that conjugate addition of lithiated allyl sulfone 5 to unsaturated esters of type 2 takes place α-regioselectively and almost exclusively in an anti fashion (where the syn and anti

• by X-ray analysis) to have the 3R,4S absolute configuration [1]. It was important to examine the effect of other aromatic substituents Ar in amino-substituted sulfone 1 and their influence on this remote induction of chirality, in the hope of further improving the remote diastereoselectivity. We

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

• -addition to α,β-unsaturated esters, ketones, sulfone, nitriles and propynoates. Supporting Information Supporting Information File 83: Experimental procedures, full spectroscopic data and spectra. Supporting Information File 84: Spectra. Acknowledgements Support of our work by the Loker Hydrocarbon

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

• University, Private Bag 11 222, Palmerston North, New Zealand 10.1186/1860-5397-3-39 Abstract We have developed a general strategy for the synthesis of 2,5-syn disubstituted pyrrolidines that is based on the multi-faceted reactivity of the sulfone moiety and a 5-endo-trig cyclisation. This methodology was

• , such as tetrahydrofurans and pyrrolidines, makes these motifs attractive targets for synthesis. Over the last decade we have developed a powerful general strategy for the preparation of such compounds based upon the multi-faceted reactivity of the sulfone group and the formally disfavoured 5-endo-trig

• mode of cyclisation. [1][2][3][4][5][6] The methodology allows the conversion of epoxides (X = O) or aziridines (X = N-PG) (2) into the desired trisubstituted tetrahydrofurans or pyrrolidines (5) via a series of sulfone-mediated transformations (Scheme 1). Ring-opening 2 with the sulfone-stabilised