ChemInform Abstract: NUCLEOPHILIC SUBSTITUTION AT TRICOORDINATE SULFUR(IV), STEREOCHEMISTRY OF DIALKYLARYLSULFONIUM SALT FORMATION FROM ALKYL ARYL SULFOXIDES

Abstract

Die cis‐ und trans‐Isomeren des Dihydrobenzothiophenoxids (I) werden zu den entsprechenden Methoxysulfoniumsalzen (II) alkyliert und nachfolgend mit Methylmagnesiumbromid bei ‐78°C oder mit Dimethylcadmium bei Raumtemperatur zu den Dimethyldihydrobenzothiopheniumtetrafluoroboraten (III) (cis‐ und trans‐Isomeres) umgesetzt.

Concerted nucleophilic aromatic substitutions

“…More broadly, concerted nucleophilic substitution reactions at sp 2 carbons have long been established for reactions of vinyl halides, 7–11 as well as acyl, 12–24 phosphorus, 25–29 and sulfur group transfer reactions. 30–34 In the context of S N Ar reactions, Williams et al have shown that the quasi-symmetric 1 addition of substituted phenoxides to phenoxytriazines is concerted, 35,36 while the apparently analogous addition of pyridines to pyridyltriazines is stepwise. 37,38 For many other reactions, computations 39–50 predict concerted mechanisms, contradicting the textbook view that S N Ar reactions proceed via stepwise addition-elimination mechanisms.…”