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Conditions are established for the preparation in yields approaching quantitative of 2.5-dilithio-furan and -thiophen. The effects of changes in reaction conditions on the ratesof hydrogen-lithium exchange for furan and thiophen have been investigated and are discussed in detail. The appearance of a 2.4-dilithio-intermediate, peculiar to N-methylpyrrole, has been explored, and optimum conditions are presented for the syntheses of both 2,4-and 2.5-intermediates. 3-Methylfuran and 3-methylthiophen are similar to the parent heterocycles in their hydrogen-lithium exchange properties. The results of applying the procedure found to produce high yields of dilithio-products to a further eight heterocycles are described. Oxford OX1 3QYDIRECT synthesis of lithio-derivatives of aromatic heterocycles by proton abstraction with an alkyl-lithium has been known for some years.lU,* Early report^,^,^ however, describe the production only of monolithiospecies in low yields. Only for N-methylpyrrole has the direct formation of a (2,5-) dilithio-derivative been recorded? though the intermediacy of 2,541ithiofuran is (a)

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