Priorities rings

The highest priority ring disconnective T-goals for 272 are those which disconnect a cocyclic 5,5-fusion bond and offexendo bond pair. The internal ketene-olefin cycloaddition in tactical combination with the Baeyer-Villiger transform is well suited to the double disconnection of such a cyclopentane-y-lactone ring pair. 

In the Z stereoisomer the two lower priority substituents—the methyl group and the hydrogen—are on the same side of the double bond In the E stereoisomer these substituents are on opposite sides of the double bond The ring carbons are the higher ranking substituents at each end of the double bond y... 

The position of substituents is indicated by numbers, with the lowest locant possible given to substituents. When a name is based on a recognized trivial name, priority for lowest-numbered locants is given to substituents implied by the bivial name. When only two substituents are present on a benzene ring, their position may be indicated by o- ortho-), m- meta-), and p- (para-) (and alphabetized in the order given) used in place of 1,2-, 1,3-, and 1,4-, respectively. 

TABLE 1.5 Trivial Names of Heterocyclic Systems Suitable for Use in Fusion Names Listed in order of increasing priority as senior ring system. 

An aldehyde group is denoted by the prefix formyl- when it is attached to a nitrogen atom in a ring system or when a group having priority for citation as principal group is present and part of a cyclic system. 

Radicofunctional nomenclature can be used when a carbonyl group is attached directly to carbon atoms in two ring systems and no other substituent is present having priority for citation. 

Sultones and Sultams. Compounds containing the group —SOj—O— as part of the ring are called -sultone. The —SOj— group has priority over the —O— group for lowest-numbered locant. 

Similarly, the —SOj—N= group as part of a ring is named by adding -sultam to the name of the hydrocarbon with the same number of carbon atoms. The —SOj— has priority over —N= for lowest-numbered locant. 

Many of the observations discussed above clearly warrant further investigation. In particular methods for controlling the Z -selectivity of the ring-closure are of high priority. Recent reports [27] discussing the precise mode of action of the ruthenium initiators provide a solid foundation upon which these future studies can be built and success in this area will strengthen even further the already powerful RCM process. 

The ring systems are treated as branched chains and phenyl group is treated for the purpose of determining its priority as though it had one of the Kekule s structures... 

On examining this compound (Sect. IV-B), we found an enantiomorphic difference between the ring ligands of C(l). It can be used to derive a priority order for the proximal carbon atoms of C(l). By provisionally assigning them different priorities one can determine which preference order induces the R, and which the S, configuration at C(4). This induced sense of chirality is mere... 

---