Amides Barbier additions

The Sml2-mediated intramolecular Barbier addition to amides is less common Fadel reported the diastereoselective cyclisation of chloroimide 122,137 while Ha carried out an intramolecular Barbier addition to the carbonyl of cyclic imide 123 (Scheme 5.86).138... 

Although Curran s rate data for the reduction of radicals to organosamar-iums allow for an element of predictablity,2 problems can arise when multifunctional substrates are involved. For example, in the attempted intramolecular Barbier reaction of alkyl iodide 13, treatment with Sml2 results in the formation of side product 15 in addition to the expected product cyclohexanol 14 (Scheme 3.7).8 In this case, the p-keto amide motif in 13 is reduced at a rate competitive with alkyl iodide reduction, indicating that there are likely two mechanistic pathways through which the reaction proceeds a thermodynamic pathway initiated by reduction of the R I bond providing the... 

Intramolecular Sml2-mediated Barbier Reactions Involving Addition to Esters and Amides... 

Functionally substituted benzylic, allylic, and vinylic compounds containing alkoxides, esters, ethers, nitriles, or amides can be reacted with halosilanes under Barbier conditions using HMPT to yield C- and O-silylated products, 1,2- or 1,4-addition products, as well as reductive dimers. Radical and anionic intermediates are postulated, based on SET reactions from the metal, and multiple silated species can be obtained. The use of the TMSCl-Mg-HMPT system has been extensively investigated by Galas group [85] at the University of Bordeaux, and their work has greatly advanced the science of the Barbier reaction with silanes. 

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