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Lithiation with n-BuLi occurs selectively at the 2-position, giving e.g. on carboxylation, 3-bromothiophene-2-carboxylic acid in good yield: Synthesis, 327 (1980). With 2 eq. of n-BuLi the dilithio-derivative is obtained, providing a useful route to 2,3-disubstituted thiophenes: Synthesis, 545 (1972)./n
Metallation with LDA at low temperature results, not in the expected 5-lithio-derivative, but in rearrangement to 2,4-dibromo-5-lithiothiophene, an example of the "base-catalyzed halogen dance": Synthesis, 771 (1989):/n
Hazard Statements: H315-H319
Causes skin irritation. Causes serious eye irritation.
Precautionary Statements: P280a-P264-P305+P351+P338-P321-P332+P313-P337+P313
Wear protective gloves and eye/face protection. Wash thoroughly after handling. IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing. Specific treatment (see label). If skin irritation occurs: Get medical advice/attention. If eye irritation persists: