| Abstract
| - 4-(1-Cycloalken-1-yl)-1,2-dialkoxybenzenes 8,10, and 11 and5-(1-cycloalken-1-yl)-1,3-benzodioxoles12−15 react with the semisquaric halides 5a and5b in a dehydrative annulation process to givethe annulated α-halobenzocyclobutenones 9a,band 16a,b−21a,b in poor to goodyields (20−76%).The reaction failed with alicyclic−aromatic dienes having no oronly one alkoxy group in the benzenering. The dehydrative annulation process could be extended to4-(3,4-dimethoxyphenyl)-1,2-dihydronaphthalene (24), affording the highly annulatedα-chlorobenzocyclobutenone 25 in 50%yield. In the case of 5-(1-cyclobuten-1-yl)-1,3-benzodioxole(22), reaction with the semisquarichalides 5a,b yielded thedicyclobutanaphthodioxole-1,2-dione (23) as the soleproduct in adehydrochlorinative annulation process. A reaction pathway hasbeen suggested for the dehydrativeannulation process. Several of the annulatedα-halobenzocyclobutenones prepared were submittedto selected chemical transformations. Thus, the reaction withtributyltin hydride afforded theannulated benzocyclobutenones 26a−f in excellent yields(74−78%), and treatment with silvertrifluoroacetate afforded the α-(trifluoroacetoxy)benzocyclobutenones27a−c in 71−79% yields.
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