The Photochemistry of Acyl Azides; X: Aroylnitrenes for Heterocycle Synthesis

Abstract

Stereoselective cycloaddition of aroylnitrenes, generated by photolysis of the corresponding azides 2a,b with the racemic mixtures of cyclic enol ethers 5b and 5c was achieved with the formation of oxazolines 8. Both the chiral auxiliary attached to the aroylnitrene and the substituent in the substrate is necessary in order to selectively allow the formation of the trans-adducts 8. The cycloaddition of aroylnitrenes bearing chiral auxiliaries with ketones did not occur stereoselectively. Benzoyl azides bearing a neighbouring amide group were found to react unexpectedly by intramolecular insertion into the N-H bond.

Key words

acyl nitrenes - photolysis - enolether - ketone - chiral auxiliaries - heterocycles

References

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8

Experiments carried out with benzoylnitrene and N-cyclo-hexyl, N-i-propylbenzamide in MeCN revealed that the amide was not attacked by the nitrene.