In the past 10 years, organic bismuth reagents have been proved to be a better arylation reagent, which is characterized by mild reaction conditions and tolerance to the influence of other functional groups. Triarylbismuth(Ⅴ) derivatives are highly efficient reagents for nucleophilic aryl substitution via a coordination coupling mechanism, and these reactions occur selectively at the ipso position. Typical arylation reactions include C-, N-, and O-arylation reactions.
Under alkaline or neutral conditions, phenols, enols, etc. can undergo C-arylation reactions with triarylbismuth (Ⅴ) derivatives or tetraphenylbismuth derivatives; using Cu as a catalyst, N-arylation of amines can be carried out, while imides and lactams can be arylated smoothly under alkaline or neutral conditions without a catalyst. Pentavalent organobismuth compounds are also effective reagents for the O-arylation of phenols, enols, and alcohols, and the arylation of phenols with electron-withdrawing substituents is generally dominated by O-arylation.
Finet et al. studied the activity of trimethoxyphenyl bismuth derivatives in typical C-, N- and O-arylation reactions, and believed that the electronic factor was not the bismuth-mediated arylation reaction The main limiting factor, breaking the traditional understanding that organic bismuth arylation reagents can only transfer aryl groups to electron-withdrawing and electrically neutral substituents. High regioselectivity and mild reaction conditions make these reagents attractive for biopharmaceutical synthesis.
Tetraphenylbismuth fluoride (Ph4BiF) is a new and effective reagent for regioselective α-sulfenylation of carbonyl compounds, with yields ranging from 82% to 99%. Using ultra-high-valent Ar3BiCl2 under the action of phosphine, the regioselective aryl substitution reaction of enone and enal was completed through nucleophilic interaction to generate α-aryl enone and enal. The yields of products reacted with cyclohexenone, cyclopentenone and crotonaldehyde are 44%-93%, 62%-89% and 49%-70%, respectively. Finet et al. used BiⅤ compounds for the first enantioselective C-arylation of substituted enols. The arylation reaction of aminobenzanilide with triarylbismuthane occurred on the amino N instead of the amide N, and the diarylamine could be obtained in high yield by heating under reflux.
Tag:   Organic Bismuth Organic Bismuth Compound
