Benzotropone synthesis

Benzotriazolium tetrachlorocobaltates crystal structure, 5, 676 Benzotrifuroxans molecular dimensions, 6, 397 N NMR, 6, 398 photoelectron spectra, 6, 399 Benzotropones synthesis, 2, 308 2H-Benz[e][l,2]oxaborins benzo fused synthesis, 1, 659 synthesis, 1, 659... 

The dihalocyclopropane route is the method of choice for the synthesis of benzocyclopropenes and linearly fused cyclopropanaphthalenes, but is unsuccessful for angular cyclopropa[u]naph-thalene. Treatment of l,l-dichloro-la,2,3,7b-tetrahydro-l/f-cyclopropa[a]naphthalene(5) with potassium /ert-butoxide gave a mixture of 1-chloromethylnaphthalene, 1-terr-butoxymethyl-naphthalene and 2-terf-butoxy-l-chloromethylene-l,2,3,4-tetrahydronaphthalene, but none of the expected cyclopropa[n]naphthalene. The failure of the reaction has been attributed to difficulties in the aromatization. Isomerization of the initially produced cyclopropenyl double bond into the cyclohexane ring would require disruption of the aromatic character of the adjacent benzene nngT t-r>> 62 Similarly, attempted aromatization of l-chloro-l,2,3,7b-tetra-hydro-l//-cyclopropa[a]naphthalene (6) with 2,3-dichloro-5,6-dicyanobenzoquinone or via N-bromosuccinimide bromination followed by reaction with base afforded 4,5-benzotropone instead of cyclopropa[fl]naphthalenc. ... 

A highly efficient synthesis of [2,3]benzotropone (69) has been based on carbene addition and ring expansion, as shown in Scheme 10. ... 

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