Sulfonyl Acetylenes as Alkynylating Reagents Under Radical or Anionic Conditions

• Published in: European journal of organic chemistry 2014-03, Vol.2014 (8), p.1577-1588
• Main Authors: García Ruano, José Luis, Alemán, José, Parra, Alejandro, Marzo, Leyre
• Format: Article
• Language: English
• Subjects: Alkynes; anti-Michael additions; C-H activation; Nucleophilic addition; Radical reactions; Synthetic methods
• ISSN: 1434-193X; 1099-0690
• DOI: 10.1002/ejoc.201301483

We provide a summary of the literature describing the use of β‐substituted sulfonylacetylenes as efficient alkynylation reagents in their reactions with radical or anionic species. Such alkynylation is due to the unexpected behavior of ethynyl sulfones, which undergo “anti‐Michael” addition of radicals and organolithium reagents and subsequent elimination of the sulfinate moiety. The reaction behavior of alkyl radicals, generated by different procedures, allows the alkynylation of any kind of C(sp3), C(sp2), and C(sp) carbon atoms, being especially efficient for α‐positions to heteroatoms With organolithium reagents alkynylation can be achieved with very few restrictions, providing substituted acetylenes or conjugated enynes of any kind in high yields under very mild conditions. Ynol ethers and alkynylphosphonates are also accessible through reactions with metal alkoxides and trialkyl phosphites, respectively. We summarize a powerful methodology for the alkynylation of C(sp3), C(sp2), and C(sp) carbon atoms, as well as some heteroatoms, with alkynylsulfones. It is based on the fact that β‐substituted sulfonylacetylenes undergo unexpected anti‐Michael addition of organolithiums and radical species, giving intermediates that evolve into alkynyl derivatives in situ by elimination of the anion or radical TolSO2.