Further Studies on the [1,2]-Wittig Rearrangement of 2-(2-Benzyloxy)aryloxazolines

The behaviour of 14 ortho-functionalised 2-aryloxazolines (11 of them prepared and characterised for the first time) with butyllithium has been examined. Significant limitations to the Wittig rearrangement of such systems are revealed. In terms of asymmetric Wittig rearrangement, good diastereoselectivity is obtained with a valine-derived 4-isopropyl oxazoline, but this is compromised by racemisation upon hydrolysis. More encouraging selectivity is achieved in the Wittig rearrangement of an acyclic phenylalanine-derived ortho-benzyloxy benzamide.

Automated summary

The limitations of the reaction between 14 ortho-functionalised 2-aryloxazolines and butyllithium were investigated, revealing challenges in the Wittig rearrangement. While good diastereoselectivity was achieved in some compounds for asymmetric Wittig rearrangement, racemisation issues were encountered upon hydrolysis.