Photoreactions of benzocyclopropene (1) with thiocyanogen and iodine afforded 1,6-dithiocyanato-( 4) and 1,6-diiodocycloheptatriene (7), respectively, in good yields, whereas thermal reactions gave 2-thiocyanatobenzyl thiocyanate (5) and 2-thiocyanatobenzyl isothiocyanate (6) from thiocyanogen and 2-iodobenzyl iodide (8) from iodine. Disodium 1,3, obtained by reduction of 4 with sodium in liquid ammonia was converted into mediumto large-membered ring sulfur heterocycles (thiacrown compounds) 10-15 by reactions with diiodomethane, 1,2-dibromoethane, and cis-1,2-dichloroethylene. Metal-catalyzed cross coupling reactions of 7 with Grignard reagents gave mono-and dialkylcycloheptatrienes and the reactions of 7 with copper bis-(trimethylsilyl)amide yielded l-alkyl-6-[bis(trimethylsilyl)amino]-l,3,5-cycloheptatrienes. An improved procedure for the preparation of 1 was also described.In connection with our study on bridged heterocyclic compounds,1 2"3 we required a general synthetic method of cycloheptatrienes having a variety of substituents at the 1-and 6-positions. Although some examples of 1,6-disubstituted cycloheptatrienes have been reported,4 no general synthetic method has been known. Recently Vogel and his co-workers reported a useful synthetic method of cycloheptatriene-1,6-dicarboxylic acid and its application to the preparation of some 1,6-disubstituted cycloheptatrienes,5 but this method is mostly restricted to the synthesis of carbon-substituted derivatives. We have found that the photoreaction of benzocyclopropene (1) with thiocyanogen or iodine gives 1,6-dithiocyanatoor l,6-diiodo-l,3,5-cycloheptatriene, respectively, in a good yield and these compounds can be converted into various kinds of 1,6-disubstituted cycloheptatrienes.6,7 Results and DiscussionSynthesis of 1,6-Dithiocyanato-and 1,6-Diiodocycloheptatrienes. If the activated "double bond" of benzocyclopropene (1) reacts with a reagent X2 in such a way as shown in eq 1, it would provide a very useful approach to 1,6-disubstituted cycloheptatrienes. A literature 1 2 survey suggests, however, that the reactions with electrophilic reagents X2 lead to the formation of a product of type 3 instead of 2.8 The only exception is the reaction 3

2): A powerful stream of phosgene was passed into the suspension of ( I ) (46.8 g, 0.4 mol) in tetrahydrofuran (THF) (600 mL) at 40°C until (1) was in solution (ca. 30 min). After 1 hours purging with anhydrous N2 the solvent was removed in uacuo, the residue taken up in a little THF, and the solvent once again removed by distillation in vacuo (removal of hydrogen chloride!). (2) was dried for 30 min at 40°C in uacuo; the yield was quantitative.(5): The solution of (2) (ca. 0.4 mol) in THF (400 ml) was added dropwise to a vigorously stirred mixture of ( 3 . HCI) (55.8 g, 0.4 mol), triethylamine (90.9 g, 0.9 mol) and CHCI3 (500 mL) (2L three-necked flask) at -70 to -60°C. After 3 hours stirring at -70°C and 30 min at room temperature the triethylamine hydrochloride was separated off by suction, the solvent removed from the solution by distillation in uacuo (40 O C bath temperature), and the residue was taken up in 1700 mL toluene. The resulting solution and then suspension was heated for 12 h under reflux with (efficient mechanical) stirring and then cooled to 0°C; (5) was recovered by suction, washed several times with ether, and then dried at 100°C in uacuo. Yield 57 g (91%). For [*I Prof. Dr. R. Okazaki [+I, DipLChem. M. 0-oka,

Die Reaktion des Dithioacetals (Ia) bzw. der Dithioimidocarbonate (Ib)‐(Id) mit aktiven Acetylenen (II), (IV) bzw. Olefinen (VI) liefert Cycloaddukte (III), (V) bzw. (VII); mit Tetracyanethylen (VIII) entstehen dagegen die konjugierten Verbindungen (IXa) bzw. (IXb) + (X).

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