Synthesis of Unsymmetrical, gem-Disubstituted Bisamides
摘要:
The addition of Grignard reagents to isocyanates allowed for the first successful synthesis of ketone-derived unsymmetrical, gem-disubstituted bisamides. The key to success was the in situ generation of the isocyanates under mild reaction conditions via Lossen rearrangement from the corresponding hydroxamic acids.
Synthesis of Sterically Hindered N-Acylated Amino Acids from N-Carboxyanhydrides
摘要:
Sterically hindered N-acyl, gem-disubstituted amino acids are easily prepared via the addition of organometallic reagents to N-carboxyanhydrides (NCA). The process tolerates a wide variety of functional groups and allows the synthesis of amide products not readily accessible by traditional acylation chemistry. The existence of an isocyanate intermediate was established by in situ IR spectroscopy.
An approach to α,α-disubstituted α-amino acids is reported. The key step is allyl cyanate-to-isocyanate rearrangement. As demonstrated, the resultant allyl isocyanates can be directly trapped with various nucleophiles, for instance, alcohols, amines, and organometallic reagents, to provide a broad range of N-functionalized allylamines. The developed method has been successfully applied in the synthesis