Cycloheptadiene and Its Simple Derivatives

The generation of 465 is also possible from l-bromo-7-(trimethylsilyl)cyclohep-tene (471) and tetrabutylammonium fluoride. This was shown by the reaction in the presence of DPIBF furnishing 475 [53], These products also resulted when both 7-bromo-7-(trimethylstannyl)norcaranes (472), admixed with DPIBF, were heated at 162 °C in C6D6 [186]. In the absence of DPIBF, the dimer 474 of 465 was formed in 

Two groups [64, 184] have pursued the query of whether the base-induced dehy-drohalogenations of the 1-halocycloheptenes 468 generate also cycloheptyne besides 465. This does occur but the extent depends on the substrate (468a, b or c), the solvent and the kind of the base. Bottini et al. [184] treated 468a-c at 65 °C with KOtBu in THF and also in DMSO as solvent. In all cases, 474 was the major product, indi- 

468a to the corresponding enamine 482 in yields of 65 and 55%, respectively, and the dimer 474 of 465 could not be observed. It was not established whether 465 or cycloheptyne acted as the decisive intermediate. 

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