Fused Ring and Bridged Fused Ring Nomenclature
(IUPAC Recommendations 1998)


Contents of Section

FR-0. Introduction
References for this Section


These recommendations constitute a comprehensive documentation for naming fused ring systems and bridged fused ring systems. It expands and extends the recommendations given in rules A-21, A-22, A-23, A-34, B-3 of the IUPAC Nomenclature of Organic Chemistry, Sections A, B, C, D, E, F and H, 1979 and rule R-2.4.1 of A Guide to IUPAC Nomenclature of Organic Compounds, 1993. Any ring system with two or more rings ortho- or ortho- and peri-fused together may be named by these recommendations. Two rings which are ortho-fused together have only two atoms and one bond in common. The nomenclature of spiro systems and von Baeyer nomenclature will be considered in separate recommendations. error details

. Introduction

The general principles for naming polycyclic fused ring systems were proposed by Patterson (ref 1). These proposals were developed by a joint committee of the American Chemical Society and National Research Council and were approved by the IUPAC Committee on Organic Nomenclature before publication (ref 2). When sections A and B of the Nomenclature of Organic Chemistry (ref 3) were prepared this technique for naming polycyclic fused ring systems was adopted.

Chemical Abstracts Service (CAS) has developed this method to cover the more complex examples encountered in its work. These extensions were documented in the Ring Index (ref 2, 4) and in Chemical Abstracts (ref 5) while additions to the Ring Index were listed at first in just Chemical Abstracts (ref 6) and then in the Parent Compound Handbook (ref 7); they are now listed in the Ring Systems Handbook (ref 8). Some long established names used by CAS are retained by them although they would not be so named today. Beilstein too has had to extend and develop fusion nomenclature.

This document has been prepared from the sources mentioned above, and material from the Chemical Abstracts Service Substance Name Selection Manual. Assistance by CAS staff members is gratefully acknowledged.

Differences between the recommendations in this document and current CAS or Beilstein practice are indicated where appropriate.

Basic techniques for naming polycyclic fused ring systems are considered in a number of places in the 1979 IUPAC rules (ref 3). For hydrocarbons rules A-21, A-22, and A-23 cover the fused ring parent hydrides, which may then be used for the names of bridged systems (A-34). Heterocyclic examples are named using the extended Hantzsch-Widman system (ref 9) and selected trivial names (B-2.11 and Table IV in the appendix of Section D of ref 3, see also ref 3a, R-2.4.1) for heterocyclic components. Details of the fusion procedure are given in rule A-21.5 and B-3 (See also ref 3a, R-2.4.1). Replacement nomenclature is described in rules B-4, B-6 and D-1.6 (See also ref 3a, R-1.2.2 and R-

This document provides a unified treatment of heterocyclic and hydrocarbon polycyclic fused ring systems with recommendations for the naming of complex examples not covered by the 1979 IUPAC rules. All names are for fused ring systems with the maximum number of non-cumulative double bonds even though the system may only be known in the form of a partially or fully hydrogenated derivative.

Structures in this document are drawn as far as possible with undistorted rings. It should be noted that the use of distorted ring shapes is only necessary for the orientation of ring systems prior to numbering the system (FR-5).

In this document no restriction is placed on when fusion nomenclature may be applied. Previously (rule A- 21.3 of ref 3) it was restricted to systems which contain at least two rings of five or more members.

References for this Section

1. A.M. Patterson and C.E. Curran, A system of organic nomenclature, J. Am. Chem. Soc. 39, 1623-1638 (1917).

2. A.M. Patterson, Proposed international rules for numbering organic ring systems, J. Am. Chem. Soc. 47, 543-561 (1925); Rec. trav. chim. Pays-Bas 45, 1-18 (1926); A.M. Patterson, Nomenclature of parent ring systems, J. Am. Chem. Soc. 50, 3074-3087 (1928); A.M. Patterson and L.T. Capell, The Ring Index, Reinhold, New York, 1940, p. 599-611; The Chemical Society (London); The French Chemical Society.

3. IUPAC Nomenclature of Organic Chemistry, Sections A and B, 1st edition, 1958; 2nd edition, 1966; 3rd edition (combined with section C), 1971; 4th edition (combined with sections C, D, E, F and H), 1979.

3a. A Guide to IUPAC Nomenclature of Organic Compounds, Recommendations 1993, Blackwell Scientific Publications, 1993.

4. A.M. Patterson, L.T. Capell and D.F. Walker, The Ring Index, 2nd edition, American Chemical Society, Washington, D.C., 1960; supplement 1, 1963; supplement 2, 1964; supplement 3, 1965.

5. Chemical Abstracts, Subject Index, vol. 56 (1962); vol. 66 (1967): Index Guide, appendix IV, vol. 76 (1972); vol. 76-85 (1972-76); 1977; vol. 86-95 (1977-81).

6. Chemical Abstracts, Index of Ring Systems, vol. 56-65 (1962-66); and subsequent indexes.

7. Parent Compound Handbook, Chemical Abstracts Service, 1977 and subsequent additions and corrections.

8. The Ring Systems Handbook, Chemical Abstracts Service, 1984; latest edition 1993, latest supplement May 1997.

9. IUPAC, Revision of the extended Hantzsch-Widman system of nomenclature for heteromonocycles, Pure Appl. Chem. 55, 409-416 (1983), see also ref 3a, pp. 40-44.

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