Unexpected transformation of spiro-3-cyanomethyl-3-methyl- 1,2,3,4,5,6-hexahydrobenzo[f]isoquin- olinium-1,2'-(1',2',3',4'-tetrahydro- naphthalen-1'-one) chloride to spiro- 3,4,5,6-tetrahydro-2H-benzo[h]chromene-2,2'-(tetrahydronaphthalen-1'-one)
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In a study of sigmatropic transformations of quaternary salts of various tetrahydropyridinium derivatives, we have discovered an unexpected cascade transformation of spirohexahydrobenzo[f]isoquinoli-nium-1,2'-(tetrahydronaphthalen-1'-ne) chloride (1) into spirotetrahydro-2H-benzo[h]chromene-2,2'-(tetrahydro-naphthalen-1'-one) (2). This reaction proceeds in the presence of moist triethylamine upon heating salt 1 in moist dioxane at reflux for 20 h. The structure of compound 2 isolated chromatographically in 40% yield was established unequivocally by GC/MS and 1H NMR spectroscopy as well as by comparison with the data of Quail et al. .
The reaction cascade leading to the final spiro compound 2 probably begins with hydration of quaternary salt 1 and formation of the 10b-hydroxy derivative, which then undergoes the retroaldol condensation to give a double Mannich base. Then, this double Mannich base undergoes deamination to give an intermediate 2-methylene-α-tetralone. This intermediate ...
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- Unexpected transformation of spiro-3-cyanomethyl-3-methyl- 1,2,3,4,5,6-hexahydrobenzo[f]isoquin- olinium-1,2'-(1',2',3',4'-tetrahydro- naphthalen-1'-one) chloride to spiro- 3,4,5,6-tetrahydro-2H-benzo[h]chromene-2,2'-(tetrahydronaphthalen-1'-one)
Chemistry of Heterocyclic Compounds
Volume 46, Issue 1 , pp 123-124
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