Meisenheimer rearrangement of azetopyridoindoles. VII. Ring expansion of 2-phenylhexahydroazeto[1',2':1,2]pyrido[3,4-b]indoles by oxidation with m- chloroperbenzoic acid

Article abstract of DOI:10.1248/cpb.43.1089

Oxidation of methyl (1,2-cis)-2-phenyl-1,2,4,5,10,10b- hexahydroazeto[1',2':1,2]pyrido[3,4-b]indole-1-carboxylate (8a) with m- chloroperbenzoic acid (MCPBA) (3 eq) in methylene dichloride at room temperature unexpectedly gave 4,10-dioxooctahydroisoxazolo[3,2- c][1,4]benzdiazonine (10) (44%), together with the two [1,2]-Meisenheimer rearrangement products [11 (5%) and 12 (14%)]. The structure of 10 was unambiguously established by an X-ray analysis. On the other hand, the peracid oxidation of the corresponding 1,2-trans isomer (17) gave hexahydroisoxazolo[2',3':1,2]pyrido[3,4-b]indole (18) (37%) via the [1,2]- Meisenheimer rearrangement of the N-oxide as well as dihydro-β-carboline N- oxide (19) (60%) and methyl cinnamate (20) (61%). The remarkable difference in the results of peracid oxidation between the two isomers (8a and 17) was rationalized on the basis of the molecular energy calculations using a combination of molecular mechanics (MM) and molecular orbitals (MO) methods.

Full text of DOI:10.1248/cpb.43.1089

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