We describe the synthesis of derivatives of 10, 10-dimethyl-1, 2, 3, 4, 4a, 5, 10, 10a-octahydrobenzo [g] cinnoline. Reduction of 2, 3, 4, 4a, 5, 10-hexahydro-8-methoxy-10, 10-dimethyl-3-benzo [g] cinnolone (11) in the presence of PtO, gave a mixture of cis and trans-8-methoxy-10, 10-dimethyl-1, 2, 3, 4, 4a, 5, 10, 10a-octahydro-3-benzo [g] cinnolone (70% 3a and 30% 3b). This mixture could be separated by successive fractional crystallization. The assignment of stereochemistry of the ring fusion in 3a and 3b was based on nuclear magnetic resonance spectra and comparison of reactivity of these compounds with 3-methyl-2-butenyl bromide. The reaction of 3a and its derivatives with boron tribromide and sodium bis (2-methoxyethoxy) aluminium hydride are also described.
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