Partners and International Organizations
(English)
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B, CH, CRO, CZ, D, DK, E, F, FIN, H, I, IRL, N, NL, P, PL, S, SI, UK
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Abstract
(English)
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Radical reactions and in particular cyclizations are becoming more and more popular in organic chemistry. They allow the preparation of complex compounds, for instance compounds of biological interest, in a very short reaction sequence. Within the COST D2 project, we have developed highly efficient chiral auxiliaries for radical reactions based on sulfoxides. The synthesis of enantiomerically pure material from simple and easily available starting materials was achieved. A systematic investigation of the stereoselectivity of simple intermolecular reactions of arylsulfinylated alkyl radicals was first undertaken. The influence of the aryl moiety on the stereoselectivity of the processes was studied. We found that good stereochemical control could be achieved with primary alkyl radicals when an ortho-chlorophenyl sulfoxides were used. The presence of an ortho-chlorine atom favors the s-cis conformation of the radical intermediate. In a second phase, we have applied the ortho-chlorophenyl sulfoxides to the control of cyclization processes. The method which has been developed is now used in our laboratory for the synthesis of natural products and analogs of pharmaceutical interest. During this work and in close collaboration with one our partner (M. Malacria, Paris VI), we have developed the first synthetic applications of the ß-fragmentation of 2 - sulfinylated radicals. Interestingly, the sulfoxide which is controlling the stereochemical outcome of the reaction is directly eliminated with formation of an olefin. This approach suppresses the need for the removal of the chiral auxiliary.
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