Phane nomenclature is a new method for building names for organic structures by assembling names that describe component parts of a complex structure. It is based on the idea that a relatively simple skeleton for a parent hydride can be modified by an operation called "amplification", a process that replaces one or more special atoms (superatoms) of a simplified skeleton by multiatomic structures. In this set of recommendations, multiatomic structures are fully saturated rings or ring systems or unsaturated rings or ring systems with the maximum number of noncumulative double bonds (mancude). In the amplification operation each superatom is replaced by a ring or ring system identified in the name by an "amplification prefix" attached to a stem called a "simplified skeletal name". The latter ends with the term "phane" and is formed according to the principles for deriving names of saturated hydrocarbons. Accordingly, all of the atoms implied by the skeletal name, except for the superatoms are, by convention, traditional saturated carbon atoms. An amplification prefix is derived from the name of the corresponding cyclic parent hydride by the addition of the terminal letter "a" with elision of a terminal vowel of the parent hydride name, if present. Phane prefixes thus resemble the traditional skeletal replacement ("a") prefixes, such as "oxa", "aza", etc., that indicate replacement of a single skeletal unit of structure, usually a carbon unit, by a different unit of structure.
Simplified skeletal name: cycloheptaphane
Phane parent hydride name: 1(2,7)-naphthalena-4(1,3)-benzenacycloheptaphane
The locants in front of the parentheses in the phane parent hydride name identify the positions of the superatoms in the simplified skeleton that are replaced by the ring structure specified by the amplification prefix immediately following. By the same token, they also identify the positions of the rings and ring systems in the phane parent hydride. These locants are determined by the inherent numbering of the simplified skeleton and the seniority of the rings and ring systems in the phane parent hydride. The locants within the parentheses specify the atoms of the ring structure expressed by the amplification prefixes that are linked to the adjacent normal atoms of the simplified parent skeleton.
In addition to the basic principles of phane nomenclature, Part I contains the fundamental methodology for numbering substituents and the application of skeletal replacement ("a") nomenclature for naming heterophane parent hydrides.
Systematic nomenclature of organic chemistry (refs. 1, 2) consists of various methods for building a name for a structure by assembling names that describe composite parts of its structure. Components of a systematic name describe individual parts of the structure of an organic compound and provide details of its structure. Not only do the components imply structural information, but they also provide information as to how a component is connected to the rest of the structure. This information is usually provided in terms of modifications to a parent structure; such modifications are called "operations". Different types of operations may be considered to represent steps of systematic nomenclature appropriate for different kinds of organic compounds.
Among the various types of operations, the following are important in deriving names for cyclic structures:
(a) ortho and ortho/peri-Fusion, expressed by fusion prefixes, such as "benzo" in the name "benzo[f]quinoline";
(b) Spiro union or fusion, expressed by the operational prefix "spiro" as in the name "spiro[piperidine-4,9'-xanthene]";
(c) Bridging, expressed by bridging prefixes, such as "methano" in the name "1,4-methanonaphthalene".
In addition, an operation involved in naming identical cyclic structures with only one bond linking one to another is:
Conjunctive union, expressed by prefixes such as "bi", "ter", etc., as in the name "2,2'-bipyridine".
In this publication, recommendations are given establishing another method for naming complex cyclic structures. It is based on the novel concept of reducing the complexity of a structure to a simpler ring, ring system, or even to a chain. This new method is called "Phane Nomenclature" because of the ending "phane" that is compulsory in all names involving the principles of this new method. Even though the term "cyclophane" has been used to describe a particular type of cyclic structure (ref. 3), no attempt is made in this presentation to restrict "phane" in such a sense.
The recommendations presented herein have been derived from various sources. In 1951, a proposal for describing a relatively small family of structures consisting of two or more benzene rings cyclically interconnected by carbon atoms or chains appeared (ref. 3). In the name "cyclophane" proposed for this class of compounds, the "ph" was derived from "phenylene", the name for expressing the presence of a benzene ring between two separate parts of a structure. Numerical terms were used as part of these names to specify connecting positions. This idea found acceptance, and a desire soon arose to use analogous names for structures containing rings or ring systems other than benzene. Thus, it was suggested (refs. 4, 5) that such names be characterized by the term "phane" and that names available for various rings and ring systems be used to indicate the presence of other rings. At this point the term "phane" became a class name. The use of the prefix "benzena" for denoting the replacement of a saturated atom in a cyclic structure by a phenylene group, first appeared in 1957 (ref. 6). Later, it was proposed that established hydrocarbon names be used for specification of other hydrocarbon rings (refs. 7, 8). Numerous amendments and extensions of this method have been proposed (refs. 9, 10, 11, 12, 13), many of which have been incorporated into the present recommendations. By generalization and adaptation of established nomenclature techniques, the method has finally been tailored so that it is fully compatible with existing systematic nomenclature of organic chemistry.
Among the established methods of systematic nomenclature of organic chemistry, skeletal replacement ("a") nomenclature (refs. 1a, 2a) is well known and widely used. Its operational concept is the replacement of one skeletal atom of a structure by another atom, each with its proper complement of hydrogen atoms, as in the name "3,6,9,12-tetraoxatetradecane", in which the prefix "oxa" in combination with the multiplicative prefix "tetra" indicates replacement of each of four carbon atoms of the fourteen-membered carbon chain by an oxygen atom. In a phane replacement operation, a superatom of a simplified skeleton is replaced by a multiatomic (cyclic) structural unit. Thus, this new operation represents an extension of the traditional skeletal replacement technique. By this extension, this new method becomes as versatile as substitution, i.e., the exchange of one or more hydrogen atoms for a single atom or a group of atoms. Since both replacement techniques are compatible, their use together in systematic names provides an efficient means for naming complex heterocyclic structures.
The recommendations in this report provide the basic rules necessary to ensure generation of unique and unambiguous names based on the novel concept of phane nomenclature within the framework of the traditional systematic nomenclature for organic compounds.
PhI-1 describes the fundamental concepts of the method by means of definitions of the terminology that will be needed for understanding the rules given in subsequent sections, PhI-2, PhI-3, and PhI-4.
PhI-2 is divided into two subsections that provide the basic rules for formation of phane parent name components:
PhI-2.1 the simplified skeletal name, which specifies the framework that is the parent structure for the amplification operation; and,
PhI-2.2 the amplification prefixes, which specify the amplificants, i.e., the cyclic parts of the original structures restored by the amplification operation.
PhI-3 delineates the rules for unique and unambiguous numbering of simplified skeletal structures and of phane parent hydrides.
PhI-4 gives the rules for generating heterocyclic phane parent hydride names using traditional skeletal replacement ("a") nomenclature in combination with phane nomenclature.
PhI-5 is a guide to the construction of phane parent hydride names.
The comprehensive system needs additional rules. The rules in this report will allow the application of the usual substitution operations. Rules related to the combination of phane nomenclature with other aspects of traditional systematic nomenclature, such as modification of the degree of hydrogenation, the use of indicated and added hydrogen, and stereodescriptors needed for phane names will be given in subsequent publications.
The examples given herein to illustrate details of the method have been chosen with didactic intent. As such, they far exceed the average complexity of structures that are normally encountered; however, they do illustrate that the use of this method demands some care. Furthermore, these examples will show that this new method is more convenient than existing ones for naming highly complex cyclic structures.
In the examples of phane parent hydrides that follow, the larger bold-faced numbers are the locants of the simplified phane skeleton and the small numbers are the locants of the individual amplificants. In the representations of simplified skeletons, superatoms are indicated by large dots and in PhI-4 the letter "x" represents heteroatoms that are to be described by the skeletal replacement ("a") operation.
PhI-1. CONCEPTS AND TERMINOLOGY
Definitions of terms that will be encountered in these recommendations are given below. These terms refer to types of operations, to the components of phane names, and to details of structure involved in the operations. They clearly describe the basis of phane nomenclature.
PhI-1.1. Simplification and Amplification
The fundamental operations of phane nomenclature are illustrated in the diagram shown in Fig. 1. The operation proceeding from left to right is called simplification; the reverse operation is called amplification, or phane replacement.
Fig. 1. Phane Nomenclature Conversion Diagram
The simplification operation illustrates the initial step in the process of assembling a phane parent name, i.e., nomenclaturally significant segments of a complex cyclic structure are replaced by single "atoms" called "superatoms" (see PhI-1.3), thus producing a simplified skeleton that can be named more easily. The phane parent hydride name (see PhI-1.6) is then formed from the names of components for the portions of structure so obtained, i.e., the "simplified parent skeleton" provides the phane skeletal name and the names for the amplificants designate the portions of the phane parent hydride replaced by the simplification procedure. In contrast to other bonds associated with the amplificant, the bonds marked by arrows in Fig. 1 do not disappear in the simplification or amplification operations.
PhI-1.2. Simplified Skeleton of the Phane Parent Hydride, Simplified Phane Parent Graph, Simplified Skeletal Name, and Skeletal Locants
Graph B in Fig. 1 at which simplification ends and amplification starts is called the simplified skeleton of the phane parent hydride and is represented by a simplified phane parent graph. Its name is the simplified skeletal name. A simplified skeletal name implies a specific skeletal numbering (see PhI-2.1); its locants are skeletal locants, which become the primary locants for the phane parent hydride name.
PhI-1.3. Superatom and Superatom Locant
The "atoms" of the simplified skeleton shown by the enlarged dots in positions 1 and 4 of Graph B in Fig. 1 that appear on simplification and disappear on amplification are called superatoms. Their locants in the simplified skeleton of the parent are called superatom locants (see PhI-2.3.1) and are a subset of the locant set that describes the location and orientation of the amplificants (see PhI-1.4). In graph theory, "atoms" and "superatoms" are both nodes (or vertices). Accordingly, it can be said that the simplified phane parent graph contains both monoatomic and polyatomic nodes and is a contraction of the complete formula graph (shown as Graph A in Fig. 1). The amplificants are subgraphs of the phane parent graph.
PhI-1.4. Amplificant, Amplification Prefix, and Amplificant Locant
A multiatomic unit of structure replacing a "superatom" in the amplification operation is called an amplificant; the six-membered rings in Graph A in Fig. 1 are amplificants. They are expressed in a phane parent name (see PhI-1.6) by amplification prefixes (see PhI-2.2). Each such prefix implies a specific numbering of the amplificant (see also PhI-22.214.171.124); the respective locants are called amplificant locants and are shown as the smaller numbers in Graph A of Fig. 1.
PhI-1.5. Attachment Atom and Attachment Locant
The atoms of an amplificant to which the bonds marked by arrows in Fig. 1 are attached are called attachment atoms, and their locants are attachment locants. In Graph A of Fig. 1, amplificant locants "1" and "4" are the attachment locants of the upper ring and amplificant locants "1" and "3" are the attachment locants of the lower ring (see PhI-2.3.2).
PhI-1.6. Phane Parent Skeleton, Phane Parent Name, and Phane Parent Hydride
The skeletal graph at the start of a simplification operation or resulting from an amplification operation (see Graph A in Fig. 1) is called a phane parent skeleton. Correspondingly, the combination of the simplified parent name, amplification prefixes, and the appropriate superatom and attachment locants (see PhI-2.3) is called a phane parent name. The term "parent" indicates that it may be combined with names for other components of the structure derived from the operations of systematic nomenclature of organic chemistry, such as substitutive prefixes, hydrogenation prefixes, and characteristic group suffixes; thus, the name becomes the parent for the various operations of traditional substitutive nomenclature. In the absence of such other components, the compound is a phane parent hydride, which means that the name implies the order of all bonds of the skeletal parent and thus the number of hydrogen atoms attached to each of the skeletal atoms.
(1) International Union of Pure and Applied Chemistry. Organic Chemistry Division. Commission on Nomenclature of Organic Chemistry, A Guide to IUPAC Nomenclature of Organic Compounds, Recommendations 1993, R. Panico, W. H. Powell and Jean-Claude Richer (Senior Editor), Blackwell Scientific Publications, Oxford, 1993, 190 pp. (a) R-126.96.36.199, p. 23; R-188.8.131.52, p. 43; R-184.108.40.206, p. 95. (b) R-0.2.4.2, p. 17. (c) R-220.127.116.11, especially footnote 29, p. 49. (d) R-2.4.3, p. 51. (e) R-2.4.2, pp. 49-51. (f) R-18.104.22.168, pp. 51-2. (g) R-22.214.171.124, p. 52. (h) R-0.1.8, p. 10. (i) R-126.96.36.199, p. 39; R-2.3.3 (in part), pp. 40-4; R-2.4.1, pp. 44-9. (j) R-188.8.131.52, p. 46. (k) R-184.108.40.206, p. 39; R-2.3.3 (in part), pp. 40-4. (m) R-9.3, p.182. (n) R-220.127.116.11, p. 43. (o) R-2.4.2, pp. 49-51.
(2) International Union of Pure and Applied Chemistry. Organic Chemistry Division. Commission on Nomenclature of Organic Chemistry, Nomenclature of Organic Chemistry, Sections A, B, C, D, E, F, and H, 1979 Edition, J. Rigaudy and S. P. Klesney eds., Pergamon Press, Oxford 1979, 559 pp. (a) B-4, pp. 68-70; C-0.6, pp. 123-7; D-1.6, pp. 334-6; D-5.17, p. 388; D-6.71, pp. 419-20. (b) A-2.6, p. 10, footnote; C-13.11(e), p. 99, footnote; D-4.14, p. 374, footnote. (c) A-31.1, p. 31, especially its footnote. (d) Spiro hydrocarbons, p. 37, especially its footnote. (e) A-31.1 and A-31.2, p. 31; A-32, pp. 32-4. (f) A-41.1 and A-41.2, p. 38. (g) A-41.6, p. 39. (h) C-16.11, p. 108. (i) A-11.3, pp. 16-17 (benzene); A-21 and A-22, pp. 20-7; B-2 (in part) and B-3, pp. 55-68. (j) A-34, pp. 35-7; B-15 (in part), pp. 75-6. (k) A-11.1, p. 16; B-2.12 (in part), pp. 62-3; D-4.21, p. 375; D-4.51 (in part), pp. 378-9. (m) Appendix, Table I, pp. 459-60. (n) B-14 (in part), p. 75. (o) B-10.1, p. 72.
(3) D. J. Cram and H. Steinberg, J. Am. Chem. Soc. 1951, 73, 5691-704.
(4) B. H. Smith, "Bridged Aromatic Compounds", Academic Press, New-York, 1964, Nomenclature, pp. 1-23.
(5) F. Vögtle and P. Neumann, Tetrahedron Lett. 1969, 5329-34; Tetrahedron, 1970, 26, 5847-73.
(6) H. Zahn and R. Krzikalia, Makromol. Chem. 1957, 23, 31-53; see p. 33.
(7) Th. Kauffmann, Tetrahedron 1972, 28, 5183-95.
(8) K. Hirayama, Tetrahedron Lett. 1972, 2109-12.
(9) H. Lehner, Monatsh. Chem. 1976, 107, 565-79; see p. 574.
(10) S. Misumi, Mem. Inst. Sci. Ind. Res., Osaka U., 1976, 33, 53-71.
(11) Nakazaki, K. Yamamoto, S. Tanaka, and H. Kametani, J. Org. Chem. 1977, 42, 287-91; see p. 289.
(12) N. E. Kagan, D. Mauzerall, and R. B. Merrifield, J. Am. Chem. Soc. 1977, 99, 5484-86.
(13) T. Otsubo and V. Boekelheide, J. Org. Chem. 1977, 42, 1085-7.
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