Gerhard van Swieten to Carl Linnaeus

Gerhard van Swieten to Carl Linnaeu

Diiodoindium(III) Cation, InI₂⁺, a Potent Yneophile. Generation and Application to Cationic Cyclization by Selective π‑Activation of CC

The removal of the iodide ion from indium triiodide by means of reactive Ag­(I) salts leads to the formation of the highly reactive ligandless cation InI₂⁺, which is unusual in having two vacant low-lying p-orbitals. This bivalent Lewis acidity leads to an especially high affinity for the two orthogonal π-bonds of carbon–carbon triple bonds. Consequently, the double-coordinating InI₂⁺ is an especially effective reagent for the selective activation of CC and the catalytic initiation of cationic cyclization processes. A number of such reactions are described to demonstrate synthetic utility

Reversal of the Importance of Steric and Electronic Effects in the Base-Promoted α‑Silylation of Sulfides

Lithiation of α–C-H groups in organic substrates by RLi or R₂NLi followed by silylation with R′₃SiCl generally provides analogous products regardless of the R′ group of R′₃SiCl. A striking exception using 3,4-benzothiophane as substrate depending on whether R′ is methyl, phenyl, or isopropyl is demonstrated. With R′ = Me or Ph, the geminal α,α-bis-silylated products result whereas with <i>i</i>-Pr₃SiCl the <i>trans</i>-α,α′-bis-silylated sulfide is formed. The latter pathway provides ready access to the <i>C</i>₂-symmetric enantiomers of <i>trans</i>-2,5-bis­(triisopropylsilyl)-3,4-benzothiophane

Selective Formation of Six-Membered Oxa- and Carbocycles by the In(III)-Activated Ring Closure of Acetylenic Substrates

Fifteen examples are disclosed of efficient In(III)-catalyzed six-membered ring closure leading to bi-, tri-, and tetracyclic products