Reactivity of o-styryl oxazolines with nucleophiles

Organolithiums undergo conjugated addition to the exocyclic double bond of o-styryl oxazolines. In contrast, m-styryl oxazolines are known to undergo nucleophilic substitution and addition. Alkyllithiums form o-oxazolyl alkyl benzenes while phenyllithium forms dihydrostilbenes, both in very high (70-95%) yields. ortho-3,6-Methoxy substituents enhance the reactions by stabilizing the benzylic anion. On the other hand, alkyl Grignards give very poor yields while heavier Grignards and softer lithium anions do not react at all.