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Tin for Organic Synthesis, 11. A Mild and Effective Synthesis of α,β-unsaturated Carboxamides and Sulfonamides by Electrophilic Substitution of Alkenylstannanes with Isocyanates
Niestroj, Michael,Neumann, Wilhelm P.,Thies, Olaf
, p. 1131 - 1136 (2007/10/02)
A new and effective method for the preparation of a variety of olefinic carboxamides 6a-k and N-(4-methylphenylsulfonyl)carboxamides 7a-d is described.The reaction of aryl and alkyl isocyanates 4a-c or 4-methylphenylsulfonyl isocyanate 5 with 1-alkenyltrialkylstannanes 1a-e and di-1-alkenyldibutylstannanes 2a-c in the presence of aluminium trichloride provides the corresponding N-aryl-substituted olefinic carboxamides 6a-k or the N-(4-methylphenylsulfonyl)-substituted olefinic carboxamides 7a-d in good yields.The stannyl moiety is superior to hydrogen as a leaving group and enables electrophilic ipso substitution at the vinylic system.In the case of di-1-alkenyldibutylstannanes the substitutions are also stereospecific, whereas the reactions of 1-alkenyltrialkylstannanes with isocyanates proceed with partial isomerisation. - Key Words: Electrophilic vinylic substitution / Isocyanates / α,β-Unsaturated amides, synthesis of / Carbodestannylation / Alkenylstannanes, applications of
