Bicyclic ring systems nomenclature

For clarity in the following discussion, structure (5.11) shows the numbering system of the 2,2,1-bicycloheptyl skeleton. This ring system nomenclature is based on the bridgehead carbon atoms. To name a bicyclic compound, one first identifies the two bridgehead carbon atoms and then counts the number of atoms in each bridge. Thus in structure... 

The nomenclature of ring systems containing the partially or fully hydrogenated monocyclic, bicyclic, and tricyclic fused 1,2-oxazine ring skeleton are shown in Figure 1. 

As 1,4 3,6-dianhydrohexitols are bicyclic systems, the appropriate ring-index nomenclature may also be used. The numbering of the atoms in such names differs from that used in the sugar-derived names. Furthermore, the stereochemistry for each of the anomeric centers has to be separately defined. The compounds under discussion have a 2,6-dioxabicylo[3.3.0]oc-tane framework, shown in Formula 6, and incorporates hydroxyl groups on C-4 and C-8. 

For systematizing the nomenclature of bicyclic terpene hydrocarbons, a consideration of only the fundamental parent carbon skeletons larger than the unsubstituted ring systems (Chart 8) is not adequate. The fundamental unsubstituted parent ring... 

Heterocyclic systems can be named by various methods, depending on ring size, the presence or absence of metal atoms, the availability of trivial names, etc. For this index the naming of the heterocyclic parents has generally followed the practices of IUPAC and Chemical Abstracts. Thus Hantzsch-Widman names have been employed for all monocyclic systems and for the other systems when the smallest ring size is five atoms or more, but replacement nomenclature has usually been followed for bicyclic and higher systems when they contain three- and four-membered rings. 

Figure 1 Nomenclature for bicyclic 5-5 systems with two ring junction nitrogens.

Figure 3 Nomenclature for bicyclic 6-6 systems with two ring Junction nitrogens.

Finally, reaction of borane with 1,5-cyclooctadiene gives a product where two of the B-H units have reacted with the two C=C units across the ring to give a bicyclic product (see Chapter 9, Section 9.7), 62. The name of this dialkylborane is 9-borabicyclo[3.3.1]nonane, which is often abbreviated 9-BBN or drawn as shown later. Nomenclature rules for bicyclic systems such as this are described in Chapter 9, Section 9.7. A. There are a total of nine atoms (nonane) but C9 has been replaced with boron (9-bora). All three of these boranes react as Lewis acids with an added alkene. 

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