In memory of Jun-ichi Yoshida
Abstract
Selective trapping of (4,5-dibromo-2-thienyl)lithium, known to undergo halogen dance,
was achieved in a flow microreactor. This transient thienyllithium, generated by mixing
2,3-dibromothiophene and lithium diisopropylamide at –78 °C for 1.6 seconds, reacted
with benzaldehyde. The reaction system is also applicable to other carbonyl compounds
to afford the corresponding adducts in good yields. Moreover, the established conditions
permit the conversion of 2,5-dibromothiophene into a mixture of the two constitutional
isomers. The contrasting results are discussed on the basis of the reaction pathway.
Key words
halogen dance - microreactors - dibromothiophenes - substituent effects - deprotonation
- lithiation