A Protocol for Accessing the β-Azidation of α,β-Unsaturated Carboxylic Acids

Abstract

This contribution reports the preparation and use of a new immobilized catalyst, PS-DABCOF (9), which has been specifically designed to access for the first time the efficient β-azidation of α,β-unsaturated carboxylic acids.

Synthesis of β‐Cyano Ketones Promoted by a Heterogeneous Fluoride Catalyst

“…The efficiency of the different solid fluoride sources strongly depends on the counter ion, especially if polymer‐supported, that has an influence on the availability and nucleophilicity of the fluoride ion towards silicon atom. This is not surprising, also on the basis of our previous experience on the influence of the solid polymeric support on the efficiency of an immobilized catalyst 12,15,17,19,20,22. A striking example is given by the different efficiency showed by Amberlite ® IRA 400F (a gel‐type polystyrene resin) and Amberlite ® IRA 900F (a macroreticular polystyrene resin) (Table 1, entry 2 vs. 6).…”

“…In recent years, we have focused our attention on processes proceeding via fluoride activation of silicon pronucleophiles12 in various types of addition reactions. A few examples are the Mukaiyama aldol reaction13 catalyzed by Amberlite ® IRA 900F (Amb‐F), a commercially available tetramethylammonium fluoride salt supported on a porous type polystyrene,14 the β‐azidation of α,β‐unsaturated ketones catalyzed by PS‐DABCOF 2 ,15 a bis‐ammonium fluoride salt of 1,4‐diazabicyclo[2.2.2]octane supported on gel type polystyrene resin,16 and the β‐azidation of carboxylic acids catalyzed by PS‐DABCOF,17 the mono‐ammonium fluoride derivative of 1,4‐diazabicyclo[2.2.2]octane supported on a gel type polystyrene.…”

Metal‐Free Radical Azidoarylation of Alkenes: Rapid Access to Oxindoles by Cascade CN and CC Bond‐Forming Reactions

“…Not surprisingly, attempted base-promoted conjugate addition of azide to olefin 1 a did not result in formation of product 2 a (Table 1, entries 3 and 4). [15] The differences in yield observed for 2 a after reducing the amount of oxidant from 2 equiv to 1 equiv (Table 1, entries 2 and 5) led us to investigate the optimal reaction conditions. Experiments with varying amounts of oxidant suggested that 1.2 equiv is required to achieve complete conversion of 1 a to 2 a with higher yield ( Table 1, entries 5-8).…”

Definition of green synthetic tools based on safer reaction media, heterogeneous catalysis, and flow technology

“…It has been developed and applied under SolFC to promote the direct β-azidation of α,β-unsaturated carboxylic acid, without protection/deprotection steps of the acid functionality, for the preparation of β-azido and β-aminoacids [94,95].…”