Interconversion of Nitrenes, Carbenes, and Nitrile Ylides by Ring Expansion, Ring Opening, Ring Contraction, and Ring Closure: 3-Quinolylnitrene, 2-Quinoxalylcarbene, and 3-Quinolylcarbene

David Kvaskoff; Ullrich Mitschke; Chris Addicott; Justin Finnerty; Pawel Bednarek; Curt Wentrup

doi:10.1071/CH08523

RESEARCH ARTICLE

Interconversion of Nitrenes, Carbenes, and Nitrile Ylides by Ring Expansion, Ring Opening, Ring Contraction, and Ring Closure: 3-Quinolylnitrene, 2-Quinoxalylcarbene, and 3-Quinolylcarbene

David Kvaskoff ^A , Ullrich Mitschke ^A , Chris Addicott ^A , Justin Finnerty ^A , Pawel Bednarek ^A and Curt Wentrup ^A ^B

+ Author Affiliations

- Author Affiliations

^A School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Qld 4072, Australia.

^B Corresponding author. Email: wentrup@uq.edu.au

Australian Journal of Chemistry 62(3) 275-286 https://doi.org/10.1071/CH08523
Submitted: 27 November 2008 Accepted: 19 January 2009 Published: 20 March 2009

Abstract

Photolysis of 3-azidoquinoline 6 in an Ar matrix generates 3-quinolylnitrene 7, which is characterized by its electron spin resonance (ESR), UV, and IR spectra in Ar matrices. Nitrene 7 undergoes ring opening to a nitrile ylide 19, also characterized by its UV and IR spectra. A subsequent 1,7-hydrogen shift in the ylide 19 affords 3-(2-isocyanophenyl)ketenimine 20. Matrix photolysis of 1,2,3-triazolo[1,5-c]quinoxaline 26 generates 4-diazomethylquinazoline 27, followed by 4-quinazolylcarbene 28, which is characterized by ESR and IR spectroscopy. Further photolysis of carbene 28 slowly generates ketenimine 20, thus suggesting that ylide 19 is formed initially. Flash vacuum thermolysis (FVT) of both 6 and 26 affords 3-cyanoindole 22 in high yield, thereby indicating that carbene 28 and nitrene 7 enter the same energy surface. Matrix photolysis of 3-quinolyldiazomethane 30 generates 3-quinolylcarbene 31, which on photolysis at >500 nm reacts with N₂ to regenerate diazo compound 30. Photolysis of 30 in the presence of CO generates a ketene (34). 3-Quinolylcarbene 31 cyclizes on photolysis at >500 nm to 5-aza-2,3-benzobicyclo[4.1.0]hepta-2,4,7-triene 32. Both 31 and 32 are characterized by their IR and UV spectra. FVT of 30 yields a mixture of 2- and 3-cyanoindenes via a carbene–carbene–nitrene rearrangement 31 → 2-quinolylcarbene 39 → 1-naphthylnitrene 43. The reaction mechanisms are supported by density functional theory calculations of the energies and spectra of all relevant ground and transition state structures at the B3LYP/6–31G* level.

Acknowledgements

The present work was supported by the Australian Research Council. We thank the Alexander-von-Humboldt Foundation, Germany, for a Feodor-Lynen Fellowship for UM, Dr Lisa George for assistance with some preliminary experiments, and the Centre for Computational Molecular Science at the University of Queensland for generous allocation of supercomputer time.

References

Interconversion of Nitrenes, Carbenes, and Nitrile Ylides by Ring Expansion, Ring Opening, Ring Contraction, and Ring Closure: 3-Quinolylnitrene, 2-Quinoxalylcarbene, and 3-Quinolylcarbene

Abstract

Acknowledgements

Subscriber Login