SP-2 Monospiro compounds containing two identical polycyclic components

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SP-2 Monospiro compounds containing two identical polycyclic components
Reference for this section

SP-2.1 Monospiro compounds containing two identical polycyclic components (ignoring double bonds and heteroatoms with a component named by von Baeyer nomenclature) are named by placing the prefix spirobi- before the name of the component ring system in square brackets. Locants required to define the component ring system are placed in square brackets. The established numbering system of the polycyclic component system is retained with one set primed. The location of the spiro atom is indicated in the name by the appropriate locants (unprimed first) placed in front of the name. If there is a choice lower numbers are selected. Where appropriate the system is made mancude (ref 13) after construction of the whole skeleton. If indicated hydrogen is needed to locate double bonds this is cited in front of the spiro atom locants. If there is a choice lower numbers are selected for indicated hydrogen.

Examples:

1,1'-spirobi[indene]
CAS index name 1,1'-spirobi[1H-indene]

3,3'-spirobi[indole]
CAS index name 3,3'-spirobi[3H-indole]

1H,1'H-2,2'-spirobi[naphthalene]
CAS index name 2,2'(1H,1'H)-spirobinaphthalene

7,7'-spirobi[bicyclo[4.1.0]heptane]

SP-2.2 If there is a choice of which component has primed locants, the lower number at the spiro atom is unprimed.

Examples:

1'H,2H-1,2'-spirobi[azulene]

2'H,3H-2,3'-spirobi[[1]benzothiophene]
CAS index name 2,3'(2'H,3H)-spirobi[benzo[b]thiophene]

Note The indicated hydrogen at 2' may be omitted.

4H-2,4'-spirobi[[1,3]dioxolo[4,5-c]pyran]
CAS index name 2,4'-spirobi[4H-1,3-dioxolo[4,5-c]pyran]

2,4'-spirobi[chromene]
CAS index name spiro[2H-1-benzopyran-2,4'-[4H-1]benzopyran]

SP-2.3 With components named by von Baeyer nomenclature heteroatoms are indicated by replacement nomenclature. The spiro system is named as the saturated hydrocarbon with replacement term prefixes in front of the completed spiro hydrocarbon name to indicate the heteroatoms. If there is a choice, low numbers are given to the spiro atom then to the heteroatoms. (See SP-1.8 for a more detailed treatment.)

Examples:

5,6'-dioxa-2,2'-spirobi[bicyclo[2.2.2]octane]
not 6,8'-dioxa-2,2'-spirobi[bicyclo[2.2.2]octane] (5,6'-dioxa is lower than 6,8'-dioxa)

3',6-dioxa-3,6'-spirobi[bicyclo[3.2.1]octane]
CAS index name spiro[3-oxabicyclo[3.2.1]octane-6,3'-[6]oxabicyclo[3.2.1]octane]

6-oxa-2,2'-spirobi[bicyclo[2.2.1]heptane]
CAS index name spiro[bicyclo[2.2.1]heptane-2,2'-[6]oxabicyclo[2.2.1]heptane]

3-sila-3,6'-spirobi[bicyclo[3.2.1]octane

SP-2.4 Unsaturation in a component named by von Baeyer nomenclature is indicated by the endings -ene, -diene, etc.; only the final 'e' of the saturated hydrocarbon name is elided if followed by a vowel. If there is a choice low numbers are given to (i) spiro atoms, then (ii) replacement terms, (iii) principal functional groups, (iv) double bonds.

Examples:

3,3'-spirobi[bicyclo[3.3.1]nonane]-6,6'-diene

2,2'-spirobi[bicyclo[2.2.1]heptan]-5-ene

5,6'-dithia-2,2'-spirobi[bicyclo[2.2.2]octane]-7,7'-diene

2-oxa-3,3'-spirobi[bicyclo[3.3.1]nonane]-6',7-diene

SP-2.5 If a choice for the numbering of the components remains, the normal rules for numbering the components are applied; unprimed locants are selected in preference to identical locants with a prime. (SeeSP-1.8 for a more detailed treatment. If the choice involves indicated hydrogen it should be considered between SP-1.8.5 and SP-1.8.6.)

Examples:

1H,1'H-2,2'-spirobi[naphthalen]-1-one

Note The 1H may be omitted.

2,2'-spirobi[bicyclo[2.2.2]octane]-5',7-dien-6-one
not 2,2'-spirobi[bicyclo[2.2.2]octane]-5,7'-dien-6'-one

13. IUPAC, Glossary of class names of organic compounds and reactive intermediates based on structure, recommendations 1995, Pure Appl. Chem. 67, 1307-1375 (1995).