Cahn, Ingold, Prelog rules for

By relating one compound to another by synthetic routes that had a known stereochemical consequence, many optically active molecules could be designated either D or L. Now all compounds are named unambiguously according to the Cahn-Ingold-Prelog rules for each chiral centre. 

Tables 5-13 contain 13C chemical shifts of the coumarin moiety and some other atoms in the molecular backbones of 876 coumarin derivatives. They are arranged according to the substitution patterns and basic molecular systems compiled in Fig. 18 below. Therefore, compound chiffres have been composed in such a way that the basic system (initial letter) and the substitution pattern (numbers after the letter) can be read directly the number after the hyphen indicates the hierarchical order which is given by the nature of that atom in a substituent which is directly connected to the coumarin moiety sequencing according to the Cahn-Ingold-Prelog rule. For example, D348-1 is a trisubstituted coumarin (D) carrying substituents at C-3, C-4 and C-8 (348 3-Br, 4-OH, 8-Me). Since bromine has the top position of all substituents at C-3 in all 3,4,8-trisubstituted coumarins listed, the compounds is the first entry (-1). The only exception from this rule appears in di- and tri-coumarins where the numbers after the letter indicate the positions at which the two (three) coumarin systems are connected.

One must be careful to use the word absolute configuration which does not always correspond to that defined by the Cahn, Ingold, Prelog rule. For example compounds in Table II have all the same spatial arrangement even if one of them has a different configuration in the sense of the Cahn, Ingold, Prelog rule. 

Model 11 CAHN-INGOLD-PRELOG RULES for Assigning E/Z Priorities... 

The Cahn-Ingold-Prelog rules work for inorganic compounds too but coordination complexes often have coordination numbers greater then four and may exhibit helical chirality, for example, denoted A and A (or Pand Min the Cahn-Ingold-Prelog system). The formal condition for chirality is that the molecule should not have an improper axis of rotation (i.e. a rotation + reflection axis, 5n =... 

Cahn-Ingold-Prelog rules as extended by Stanley and Baird.168,171 For instance, the diastereoisomer with intrinsic R configuration at the central metal atom is shown in Figure 9(c), for the case of a metallocene with a H2C(Cp)(9-Flu) ligand. It is important to note that chirality of type (c) requires that the two coordination positions available for the growing chain and the monomer are occupied by different ligands. This implies that compounds such as the dichloride pre-catalysts are not chiral. 

It has recently been proposed that kink sites of high Miller index metal surfaces should be considered as chiral when the step lengths on either side of the kink are unequal [22], Two such surfaces, which are not superimposable, can be defined - by analogy with the Cahn-Ingold-Prelog rules - as, e. g., Ag(643) and Ag(643). Theoretical calculations predicted that adsorption of chiral molecules should be stereospecific on such surfaces, but the only experimental evidence yet available is the electro-oxidation of d- and L-glucose on Pt(643) and Pt(531) surfaces [23]. It was speculated that with the polycrystalline metal catalyst, which contains equal numbers of (/ )- and (S)-type kink sites, preferential adsorption of a chiral modifier on one type of kink site would leave the other type of site free for catalysis. 

Determination of the absolute configuration for a 1,2-disubstituted ferrocenic and 1,2-disubstituted arene chromium tricarbonyl compounds. Carbon C bearing the priority substituent (a) is considered as the central atom, the priority order is determined following the Cahn-Ingold-Prelog rules. 

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