Ketenimines

General structure of a ketenimine

Ketenimines are a group of organic compounds with the general structure R₂C=C=NR'. A ketenimine is a cumulated alkene and imine and is related to an allene and a ketene. ^[1] When the substituents on the terminal carbon differ, the ketenimines are intrinsically chiral owing to the non-linearity of the C=N-R group.

Ketenimines can be prepared by reactions of isocyanates with Wittig reagents:

Ph₃P=CR₂ + R'N=C=O → R₂C=C=NR' + Ph₃PO (Ph = phenyl)

Similarly, aza-Wittig reagents react with ketenes to give ketenimines:

Ph₃P=NR' + R₂C=C=O → R₂C=C=NR' + Ph₃PO

This method was employed in the preparation of the first example of a ketenimine. ^[2]

Astronomical detection

The parent ketenimine (CH₂CNH) has a distinctive rovibrational spectrum. The ν₈ and ν₁₂ bands in the high-resolution FTIR spectrum are pair of Coriolis-coupled bands. They provide a rare example where intensity sharing between bands yields sufficient intensity for an otherwise invisible band (ν₁₂). ^{[3] [4]}

Further reading

• Denmark, Scott E.; Wilson, Tyler W. (2012). "Silyl Ketene Imines: Highly Versatile Nucleophiles for Catalytic, Asymmetric Synthesis". Angewandte Chemie International Edition. 51 (40): 9980–9992. Bibcode:2012ACIE...51.9980D. doi:10.1002/anie.201202139. PMC   3532842 . PMID   22968901.
• Alajarin, Mateo; Marin-Luna, Marta; Vidal, Angel (2012). "Recent Highlights in Ketenimine Chemistry". European Journal of Organic Chemistry (29): 5637–5653. doi:10.1002/ejoc.201200383.

References

1. Lu, Ping; Wang, Yanguang (2012). "The Thriving Chemistry of Ketenimines". Chemical Society Reviews. 41 (17): 5687–6305. doi:10.1039/C2CS35159E. PMID   22833018.
2. Staudinger, H.; Meyer, Jules (1919). "Über neue organische Phosphorverbindungen III. Phosphinmethylenderivate und Phosphinimine". Helvetica Chimica Acta. 2: 635–646. Bibcode:1919HChAc...2..635S. doi:10.1002/hlca.19190020164.
3. Michael K. Bane; Christopher D. Thompson; Evan G. Robertson; Dominique R. T. Appadoo; Don McNaughton (2011). "High-resolution FTIR spectroscopy of the ν8 and Coriolis perturbation allowed ν12 bands of ketenimine". Physical Chemistry Chemical Physics. 13 (15): 6793–8. Bibcode:2011PCCP...13.6793B. doi:10.1039/C0CP01816C. PMID   21116541.
4. F. J. Lovas; J. M. Hollis; Anthony J. Remijan; P. R. Jewell (2006). "Detection of Ketenimine (CH₂CNH) in Sagittarius B2(N) Hot Cores". The Astrophysical Journal. 645 (2): L137 –L140. Bibcode:2006ApJ...645L.137L. doi: 10.1086/506324 .