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The radical-chain addition of benzenethiol to the monoalkylallenes la-e and the 1,1-dialkylallenes 6 and 8 has been studied. Attack by the benzenethiyl radical occurs at C2 and C3 of lb-e in a ratio of 83:17. Increased attack (25%) at C3 occurs with tert-butylallene (la). The 1,1-dialkylallenes undergo attack only at C2. Deuterium-labeling studies indicate that the thiyl radical addition step is not detectably reversible under the reaction conditions. The internal alkene adducts 2,3,9, and 10 are the kinetically favored products. Rapid and reversible addition of the thiyl radical to the adducts results in complete stereochemical equilibration during the course of the reaction. The hydrogen atom abstraction step is reversible under the reaction conditions with la and 8 but not with 6 or the other monoalkylallenes. Treatment of the adducts derived from la and 8 with a catalytic

Durch Cyclisierung der Hydroxamsäurederivate (I) bzw. (III) (Darstellung beschrieben) nach den angegebenen Methoden werden die Lactame (II) bzw. (IV) erhalten (Modellversuche).

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loss of the yellow color and filtered while hot to remove the catalyst. Evaporation of the toluene left an oil, which solidified upon cooling. The solid was recrystallized from ethanol to give 50 mg (28%) of 2-ethylanthracene, mp 148-150 °C (lit.13 mp 148-150 °C). A mixed melting point with authentic 2-ethylanthracene was not depressed.Diels-Alder Reactions of Anthra[2,3-6 Jthiophene. 5,thiophene (11). Among several attempts to prepare dicyanoacetylene by published methods, the one reported by Byrd and co-workers14 was the most efficient. A solution of anthra[2,3-5]thiophene (0.40 g, 1.71 mmol) and dicyanoacetylene (0.39 g, 5.12 mmol) in toluene (35 mL) was heated under reflux for 2 h. Evaporation of the solvent following decolorization with Norit gave a yellow-white solid, which was recrystallized from benzene-toluene as white crystals: mp 234-235 °C; 0.43 g (82%); IR (Nujol) 2220 cm"* 1; NMR (acetone-d6) 7.2-S.2 (m, 8 H, aromatic CH), 6.0 (s, 2 H, C4,io-H).