1, 4‐Addition of TMSCCl3 to Nitroalkenes: Efficient Reaction Conditions and Mechanistic Understanding. Issue 25 (21st May 2014)

• Record Type: Journal Article
• Authors: Wu, Na; Wahl, Benoit; Woodward, Simon; Lewis, William
• Is Part Of: Chemistry. Volume 20:Issue 25(2014)
• Page Start: 7718
• Page End: 7724
• Publication Date: 2014-05-21
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201402394
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>Improved synthetic conditions allow preparation of TMSCCl<sub>3</sub> in good yield (70 %) and excellent purity. Compounds of the type NBu<sub>4</sub>X [X=Ph<sub>3</sub>SiF<sub>2</sub> (TBAT), F (tetrabutylammonium fluoride, TBAF), OAc, Cl and Br] act as catalytic promoters for 1, 4‐additions to a range of cyclic and acyclic nitroalkenes, in THF at 0–25 °C, typically in moderate to excellent yields (37–95 %). TBAT is the most effective promoter and bromide the least effective. Multinuclear NMR studies (<sup>1</sup>H, <sup>19</sup>F, <sup>13</sup>C and <sup>29</sup>Si) under anaerobic conditions indicate that addition of TMSCCl<sub>3</sub> to TBAT (both 0.13 <sc>M</sc>) at −20 °C, in the absence of nitroalkene, leads immediately to mixtures of Me<sub>3</sub>SiF, Ph<sub>3</sub>SiF and NBu<sub>4</sub>CCl<sub>3</sub>. The latter is stable to at least 0 °C and does not add nitroalkene from −20 to 0 °C, even after extended periods. Nitroalkene, in the presence of TMSCCl<sub>3</sub> (both 0.13 <sc>M</sc> at −20 °C), when treated with TBAT, leads to immediate formation of the 1, 4‐addition product, suggesting the reaction proceeds via a transient [Me<sub>3</sub>Si(alkene)CCl<sub>3</sub>] species, in which (alkene) indicates an Si⋅⋅⋅O coordinated nitroalkene. The anaerobic catalytic chain is propagated through the kinetic nitronate anion resulting from 1, 4 CCl<sub>3</sub><sup>−</sup> addition to the nitroalkene. This is demonstrated by the fact that isolated NBu<sub>4</sub>[CH<sub>2</sub>NO<sub>2</sub>] is an efficient promoter. Use of H<sub>2</sub>CCH(CH<sub>2</sub>)<sub>2</sub>CHCHNO<sub>2</sub> in air affords radical‐derived bicyclic products arising from aerobic oxidation.</p> </abstract>