Process for the synthesis of azetidinones

A process for preparing a compound represented by the Formula (IV):

• comprising the step of:
• cyclizing the β-(substituted-amino)amide of formula XII
• wherein X is —O—, —S— or —N(C1-C6 alkyl);
• Y is ═O or ═S;
• and R1 is alkyl, aryl or alkoxycarbonyl, and wherein Prot is a silyl protecting group with at least one silylating agent and at least one cyclizing agent which is:
• (a) selected from the group consisting of alkali metal carboxylates, quaternary ammonium carboxylates, quaternary ammonium hydroxides, quaternary ammonium alkoxides, quaternary ammonium aryloxides and hydrates thereof;
• or
• (b) the reaction product of:
• (i) at least one quaternary ammonium halide and at least one alkali metal carboxylate;
• or
• (ii) at least one quaternary ammonium chloride, quaternary ammonium bromide, or quaternary ammonium iodide and at least one alkali metal fluoride,
• wherein a quaternary ammonium moiety of the cyclizing agent is unsubstituted or substituted by one to four groups independently selected from the group consisting of alkyl, arylalkyl and arylalkyl-alkyl,
• to obtain the compound of Formula XI:
• removing the silyl protecting groups to form the compound of Formula (IV).