Reduction of 13-hydroxy-2, 3-methylenedioxy-9, 10-dimethoxy-5, 6-dihydrobenzo[
a]-acridizinium chloride (III) with zinc and acetic acid afforded
trans-2, 3-methylenedioxy-9, 10-dimethoxy-5, 6, 13, 13a-tetrahydro-8
H-dibenzo [
a,
g] quinolizine (IIa) and
cis-2, 3-methylenedioxy-9, 10-dimethoxy-5, 6, 13, 13a-tetrahydro-8
H-dibenzo[
a,
g]quinolizine (IIb). A similar reduction of 13-methoxy-2, 3-methylenedioxy-9, 10-dimethoxy-5, 6-dihydrobenzo[
a]acridizinium iodide (IV) gave only II a which is formed by the elimination of methoxy group at 13-position of IV. Sodium borohydride reduction of III and IV in methanol afforded 2, 3-methylenedioxy-9, 10-dimethoxy-5, 6, 13, 13a-tetrahydro-8
H-dibenzo[
a,
g]quinolizin-13-ol (V) and 13-methoxy-2, 3-methylenedioxy-9, 10-dimethoxy-5, 6, 13, 13a-tetrahydro-8
H-dibenzo[
a,
g]quinolizine (VI) (m. p. 200-201°
in vacuo), respectively. Reduction of 8-acetonyl-13-hydroxy-2, 3-methylenedioxy-9, 10-dimethoxy-5, 6, 13, 13a-tetrahydro-8
H-dibenzo[
a,
g]quinolizine (VII) with zinc dust and acetic acid gave IIa, but in case of α-methyl-13-hydroxy-2, 3-methylenedioxy-9, 10-dimethoxy-5, 6, 13, 13a-tetrahydro-8
H-dibenzo[
a,
g]quinolizine-8-methanol (VIII) and V the same reduction afforded starting materials. Therefore, it follows from these results that the mechanisms of dehydroxylation and demethoxylation with zinc and acetic acid differ from that of hydrogenolysis of benzyl alcohol type compounds via their tetrahydro-derivatives.
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