Aryne Insertion into a Nucleophilic-Electrophilic o-Bond

Aryne Insertion into a Nucleophilic-Electrophilic o-Bond 

During an investigation into the addition reactions of element-element o-bonds to the C—C triple bonds of arynes, Yoshida et al. observed aryne insertion into the S—Sn o-bond of stannyl sulfides (Equation 12.16) [22]. The reaction is initiated by nudeophihc attack of the sulfur atom of the stannyl sulfide on the aryne triple bond, resulhng in the formation of a zwitterion, which undergoes intramolecular nudeophihc substitution at the stannyl moiety. This affords the corresponding 2-(arylthio)arylstannane 19. 

Under similar reaction conditions, arynes can also insert into the N—Si o-bond of aminosilanes, leading to 2-silylanihne derivatives in a straightforward manner (Equation 12.17) [23]. Both, cyclic and acychc amine-derived silanes work weU in this reachon, which is initiated by a nudeophihc attack of the nitrogen moiety of the aminosilane on the aryne triple bond, forming a zwitterion which subse- 

The C—N o-bond of N-aryltrifluoroacetamides and the S—N j-bond of trifluo-romethanesulfinamides have both been found to undergo additions across the aryne triple bond to afford l-[2-(arylamino)aryl]trifluoroethanones and (2-arylamino)aryl trifluoromethyl sulfoxides, respectively (Equations 12.19 and 12.20) [25]. The presence of the CF3 moiety in the substrates proved to be crucial for these insertion reachons to occur moreover, the reactions were limited to secondary amides or sulfinamides. No insertion product was detected in the case of the tertiary amide N-methyl-N-phenyltrifluoroacetamide. 

The reaction conditions were later optimized by Danishefsky and coworkers in the condensation of bromoarene 34 with dimethyl malonate anion, where the 

---