Synthesis of 1-Cyclohept-1,2-dien-1-yl Benzene from 1-(2-iodo-, chlorocyclohept-1-en-1-yl)benzene and 1-(2-iodo-, chlorocyclohept-2-en-1-yl)benzene: Its Trapping with Diphenylisobenzofuran

Authors: MUSTAFA CEYLAN, YAKUP BUDAK, MURAT ULUKAYA, M. BURCU GÜRDERE, ESRA FINDIK

Abstract: The key compounds vinyl iodides 12a and 13a, for the generation of 1-cyclohept-1,2-dien-1-ylbezene (1), were synthesized from cycloheptanone (5). Bromobenzene was converted to the Grignard reagent, which was condensed with 5. Dehydration of alcohol 6 gave alkene 7. Hydroboration of 7 followed by oxidation with PCC afforded ketone 9, which was converted to hydrazone 10. Treatment of 10 with iodine resulted in the formation of 12a and 13a. The other precursors, 12b and 13b, were synthesized from the reaction of 9 with PCl_5. Reactions of 12a, b and 13a, b with KOtBu in a sealed tube at 185 °C gave the [2+4] and [2+2] dimer products 20 and 21, respectively. In addition, reactions of 12a, b and 13a, b with KOtBu under the same conditions in the presence of diphenylbenzoisofuran (DBI) as a trapping reagent afforded the [2+4] cycloadducts 24 and 25 in good yields.

Keywords: Substituted cyclic allene, dehydroiodination, dehydrochloration, dimerization, cycloaddition

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