Bridgehead nitrogen systems, saturated

No specific review of aromatic azapentalenes exists, though much of the work before 1960 is covered in a more general article on bicyclic heterocycles with bridgehead nitrogen atoms by Mosby6 in the Weissberger series on heterocyclic chemistry. That article makes no distinction between aromatic and saturated systems, and the present review, though not exhaustive, deals mainly with aromatic systems and covers most of the literature to the end of 1975. Nonaromatic compounds will not be treated except where they are sufficiently important. 

Quinuclidine (1) is a saturated bicyclic system with a bridgehead nitrogen atom. It has, in contrast to tertiary aliphatic amines and -substituted piperidines, a rigid structure. The atoms forming the quinuclidine ring are incapable of changing their relative positions by rotation around bond axes. These bond axes are included in the bicyclic system with each ring in the boat form. 

Crabb, T. A., lackson, D., Patel, A. V., Saturated Bicyclic 6/5 Ring-Fused Systems with Bridgehead Nitrogen and a Single Additional Heteroatom,... 

Biological pyrimidines, tautomerism and electronic structure of, 18, 199 Bipyridines, 35, 281 Boron-substituted heteroaromatic compounds, 46, 143 Bridgehead nitrogen saturated bicyclic 6/5 ring-fused systems with, 49, 193... 

Azine approach. Saturated ring systems with a bridgehead nitrogen atom are best prepared from 3,4,5,6-tetrahydroazine 1-oxides. The latter can be classified as nitrones and as such will undergo 1,3-dipolar cycloaddition reactions. 

The main interest in saturated or partially saturated compounds has been in systems having a bridgehead nitrogen atom, in particular, reduced forms of 5H-thiazolo[3,2-a ]pyridines. 

Saturated BicycHc 6/5 Ring Fused Systems with Bridgehead Nitrogen and a Single Additional Heteroatom... 

The other three chapters in the present volume all deal with bicyclic heterocycles. Dr. H. K. Pujari of Kurukshetra University in India describes condensed 4-thiazolidinones, and Professor M. A. E. Shaban and A. Z. Nasr of Alexandria University in Egypt survey the synthesis of condensed 1,2,4-triazolo heterocycles. Finally, Professor T. A. Crabb of Portsmouth, England has covered saturated bicyclic 6/5 ring-fused systems with a bridgehead nitrogen and a single additional heteroatom. None of these groups of bicyclic heterocycles has been comprehensively reviewed before. 

The quinuclidine molecule is a saturated bicyclic system having a bridgehead nitrogen atom [1-3]. In contrast to tertiary aliphatic amines and AT-sub-... 

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