Triazine reaction

In an approach to the AB rings of rubrolone 65, Boger examined the use of oxazinones as a replacement for triazines. Reaction of l,3-oxazin-6-one 66 with enamines 67 produced the corresponding pyridines 70. The reaction proceeds in a manner analogous to the triazines however, instead of losing nitrogen, these systems lose CO2 via the intermediate bicyclo[2.2.2]octanes 68. The resultant 69 then loses pyrrolidine as in the triazine example. 

Triazines, reactions of ring N-atoms with electrophiles 88AHC(43)127. 

Pyrylium salts have been found to be particularly useful starting materials for preparation of pyrido[2,l-/][l,2,4]triazines. Reaction of (102) with thiosemicarbazide <87H(26)2183>, carbono-hydrazide <86JCR(S)460>, thiocarbonohydrazide <84S697>, or amidrazones <91H(32)649> gave the bicyclic compounds (103)-(106), generally in high yields (Scheme 5). 

A very spectacular synthesis of bridged aza[10]annulenes is shown in Scheme 2. Good yields of stable annulenes are obtained from triazines carrying several electron-withdrawing substituents. In the case of less reactive triazines, reaction... 

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