Synthesis and Characterization of Bromonium Ylides and Their Unusual Ligand Transfer Reactions with N-Heterocycles

Abstract

Stable aliphatic bromonium ylides (RfSO2)2C--Br+C6H4-p-CF3 (Rf = CF3, CF3(CF2)3) have been synthesized and structurally characterized for the first time. X-ray crystallographic analyses indicated a ylide structure with an sp2 hybridization of the ylide carbanions and with little double-bond character for the ylidic bond. The bromonium ylides selectively undergo transfer of the aryl group to nitrogen heterocycles, such as pyridines, yielding N-arylpyridinium salts. This is in a marked contrast to the reaction of the iodonium ylides, which produces pyridinium ylides through transylidations.

A Persistent α‐Fluorocarbanion and Its Analogues: Preparation, Characterization, and Computational Study

“…The stabilization of the carbanion by two phenylsulfonyl groups is supported by the following observations: a) the parent carbanion I (Figure 1), studied by Henderson and others,9 has been readily prepared and proved to be highly thermostable, b) Dubenko et al 10. have reported the preparation of potassium salts of IV and V , c) later, Ochiai and co‐workers11 reported that brominated bis(perfluoroalkylsulfonyl) carbanion VI also can be crystallized as a fairly stable solid. Based on these studies, we decided to prepare the fluorine‐bearing carbanion II and study its stability under suitable conditions.…”

A Persistent α‐Fluorocarbanion and Its Analogues: Preparation, Characterization, and Computational Study

“…[3b] The stabilization of the carbanion by two phenylsulfonyl groups is supported by the following observations: a) the parent carbanion I (Figure 1), studied by Henderson and others, [9] has been readily prepared and proved to be highly thermostable, b) Dubenko et al [10] have reported the preparation of potassium salts of IV and V, c) later, Ochiai and co-workers [11] reported that brominated bis(perfluoroalkylsulfonyl) carbanion VI also can be crystallized as a fairly stable solid. Based on these studies, we decided to prepare the fluorine-bearing carbanion II and study its stability under suitable conditions.…”

Carbanions and Electrophilic Aliphatic Substitution

“…149 The bromonium ylides (38) selectively undergo transfer of the aryl group to nitrogen heterocycles, such as pyridines, yielding N -arylpyridinium salts. …”