Azonines, formation

Many other miscellaneous additions of alcohols have been described. Polar addition of methanol to 2//-pyrroles264 and to azepines265 has been observed. Photoaddition of methanol to the 1,3,4-oxadiazole 320 is followed by cycloelimination of methyl benzoate (321) to give the ylid 322.266 An adduct (323) of the ylid and the 1,3,4-oxadiazole has been isolated. Photoaddition of methanol to the quaternary ammonium salt 324 results in ring expansion and the formation of the azonine 325.267... 

Dibenzazonines have been synthesized by three general approaches (A) construction of the azonine ring from an appropriately substituted biphenyl derivative, (B) formation of the aryl-aryl bond, and (C) by rearrangement of various types of alkaloids. 

The most general methods of C-N bond formation used for heteronine formation are alkylation or Mitsunobu condensation. Azonine 213 was synthesized starting from 2-nitrobenzenesulfonamides and using conventional alkylation procedures or Mitsunobu conditions (Scheme 44) <2002SL697, 2002T6267>. 

Q 11. Ethyl l f-azonine-l-carboxylate gives different products under thermal and photochemical conditions. Explain the mechanism for their formation. 

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