Bridgehead nitrogen, tricyclic compounds

Hermecz, I., Vasvari-Debreczy, L., Tricyclic Compounds with a Central Pyrinudine Ring and One Bridgehead Nitrogen, 39, 281. 

Tricyclic Compounds Having a Bridgehead Nitrogen Atom 288... 

All the bicyclic /3-lactams included in this section have a bridgehead nitrogen atom and are formed from 1,4-disubstituted azetidinones, so this section can be considered as an extension of Section 2.04.9.3. In addition, the Wittig reaction has been extensively employed in the preparation of tricyclic and tetracyclic /3-lactams and its use is referred to in Section 2.04.11. The main use of the reaction to form bicyclic compounds has been to produce 2-substituted carbapen-2-ems. 

The biggest group of tricyclic compounds having a bridgehead nitrogen atom and extra one or more heteroatoms is the fused 4/6/6 system. Two main routes have been adopted for their synthesis either cyclization onto the nitrogen atom of a /3-lactam or by a cycloaddition process. Each of these routes can be achieved by either an intermolecular or an intramolecular reaction. 

Tricyclic Compounds with a Central Pyrimidine Ring and One Bridgehead Nitrogen... 

Tricyclic compounds with a central pyrimidine ring and one bridgehead nitrogen can be divided into three types. 

A number of linearly annelated tricyclic compounds are known as alkaloids. Certain types of tricyclic nitrogen bridgehead compounds have aroused interest because of their valuable pharmacological properties. They are also used as photographic sensitizers and fiber-reactive dyes. 

Mohrle and Gundlach - carried out the oxidative cyclization of the 2-aminobenzylamines 267 with the mercuric acetate-EDTA reagent to obtain the nitrogen bridgehead compounds 270 in 64-80% yields. The oxidation of the tricyclic compounds 270 with manganese dioxide produced the corresponding fused quinazolinones 99. ... 

Much recent work on tricyclic compounds with a central pyrimidine ring and one bridgehead nitrogen has come to the attention of the authors since this chapter was submitted for publication. The work cannot be discussed in detail, but it was felt that references should be provided. " ... 

The cyclazines (a trivial name) are tricyclic fused molecules containing a central bridgehead nitrogen and a peripheral 7r-system. The definition of aromaticity in these compounds is not as straightforward as for the simple bicyclic molecules discussed above, and a more detailed analysis of the molecular orbitals may be required. 

Photocyclization of A -(4-phenyl-4-pentenyl)monothiobarbiturate (327) afforded a mixture of l,2,3-trimethyl-9-phenyl-l,2,3,6,7,8-hexahydro-4//-pyrido[l,2-u]pyrimidine-2,4-dione and tricyclic nitrogen bridgehead compound 328 (96H(42)117). 

Treatment of tricyclic nitrogen bridgehead compounds 427 with acidified MeOH gave 7,8,9-trihydroxyperhydropyrido[l,2-a]pyrazines 428 (00T1005). 

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