Regio- and stereochemical aspects in the functionalisation of a lithiated 2-(3-chloro-2-methyl-1-propenyl)-2-oxazoline: electrophile and temperature effects

Abstract

4,4-Dimethyl-2-(3-chloro-2-methyl-1-propenyl)-2-oxazoline has been synthesized and deprotonated with LDA in THF to give the corresponding lithiated species, which has been found to react α-regioselectively with NH4Cl and alkyl halides, and γ-regioselectively with carbonyl compounds to afford α-protonated (or α-alkyl-substituted) regioisomers and vinyl epoxides, respectively. The Z diastereoselectivity of both the protonation and the alkylation reactions was usually found to increase with the temperature. Ab initio calculations, performed on both the naked lithium salt and the corresponding solvated form, support the observed regioselectivity.