Abstract
Organic phosphonium salts have served as important intermediates in synthetic chemistry. But the use of a substituent on the positive phosphorus as a nucleophile to construct C–C bond remains a significant challenge. Here we report an efficient transition-metal-free protocol for the direct nucleophilic arylation of carbonyls and imines with tetraarylphosphonium salts in the presence of caesium carbonate. The aryl nucleophile generated from phosphonium salt shows low basicity and good nucleophilicity, as evidenced by the successful conversion of enolizable aldehydes and ketones. The reaction is not particularly sensitive to water, shows wide substrate scope, and is compatible with a variety of functional groups including cyano and ester groups. Compared with the arylmetallic reagents that are usually moisture sensitive, the phosphonium salts are shelf-stable and can be easily handled.
Highlights
Organic phosphonium salts have served as important intermediates in synthetic chemistry
Intensive studies have been devoted to the exploration of efficient methods for arylation of carbonyl and imino compounds, allowing access to a-aryl-alcohols and a-aryl-amines, which are abundant in biologically active molecules[1,2]
We report a nucleophilic arylation of carbonyl and imino compounds with tetraarylphosphonium salts in the presence of caesium carbonate (Fig. 1)
Summary
Organic phosphonium salts have served as important intermediates in synthetic chemistry. We report an efficient transition-metal-free protocol for the direct nucleophilic arylation of carbonyls and imines with tetraarylphosphonium salts in the presence of caesium carbonate. Traditional arylmetallic reagents, which are usually generated in situ under Barbier-type conditions[6,7,8] or prepared in advance like arylmagnesium reagents[9,10,11], have long been used for nucleophilic addition to carbonyl or imino groups. This approach often suffers from narrow substrate scope, or the high moisture sensitivity and the strong basicity of the reagents. Mechanistic investigation reveals that the reaction is predominantly initiated by caesium carbonate
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