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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Bedingungen für die annähernd quantitative Darstellung von 2,5‐Dilithio‐furan und ‐thiophen werden erarbeitet.

Das Aminothiazol (Ia) reagiert zwar, wie in der Literatur berichtet, unter Bildung des Hydrazids (II), und dieses liefert bei der Behandlung mit HNO, das Azid (III); letzteres führt jedoch beim Erwärmen mit Acetanhydrid nicht wie angegeben zur definierten Verbindung (IV), sondern zu einem komplexen Produktgemisch.