Simple, chemoselective, and diastereoselective Reformatsky-type synthesis of α-bromo-α-fluoro-β-lactams

✍ Scribed by Atsushi Tarui; Naoto Kawashima; Kazuyuki Sato; Masaaki Omote; Yoshihisa Miwa; Hideki Minami; Akira Ando

• Publisher: Elsevier Science
• Year: 2010
• Tongue: French
• Weight: 450 KB
• Volume: 51
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/j.tetlet.2010.02.023

✦ Synopsis

The chemoselective and diastereoselective synthesis of syn-a-bromo-a-fluoro-b-lactams was achieved using the diethylzinc-mediated Reformatsky-type reaction of ethyl dibromofluoroacetate with imines. The reaction led to diastereomerically pure b-lactams in good to moderate yields (up to 78% yield) with only small amounts of aziridine derivatives. Noncyclized 3-amino-2-bromo-2-fluoro carboxylic esters, usual Reformatsky adducts, were not formed. In contrast, reactions carried out under typical Reformatsky conditions using zinc metal were poorly chemoselective, leading to mixtures of b-lactams and aziridine derivatives.