Ulrich Siemeling and colleagues, University of Kassel, Germany, have shown that stable N-heterocyclic carbenes (NHCs) can show strongly enhanced reactivities towards fundamentally important small molecules such as ammonia and carbon monoxide, which is unprecedented for diaminocarbene compounds.

The scientists demonstrate that a ferrocene-based NHC is able to add ammonia, methyl acrylate, tert-butyl isocyanide, and carbon monoxide—reactions typical of (alkyl)(amino)carbenes, but unprecedented for diaminocarbenes. They also show that even the simplest stable diaminocarbene, C(NiPr₂)₂, adds CO. This reaction provideds a new entry to the important β-lactam ring systems commonly found in antibiotics.

The newly discovered reactivity of diaminocarbenes opens the door to an exciting area of synthetically useful carbene chemistry.

• N-heterocyclic carbenes which readily add ammonia, carbon monoxide and other small molecules,
  Ulrich Siemeling, Christian Färber, Clemens Bruhn, Michael Leibold, Detlef Selent, Wolfgang Baumann, Moritz von Hopffgarten, Catharina Goedecke, Gernot Frenking,
  Chem. Sci. 2010.
  DOI: 10.1039/C0SC00451K