Spiro compound

In organic chemistry, spiro compounds are compounds that have at least two molecular rings sharing one common atom. Simple spiro compounds are bicyclic (having just two rings).^[2]^: SP-0^[3]^{: 653, 839} The presence of only one common atom connecting the two rings distinguishes spiro compounds from other bicyclics.^[4]^[3]^: 653ff ^: 839ff Spiro compounds may be fully carbocyclic (all carbon) or heterocyclic (having one or more non-carbon atom). One common type of spiro compound encountered in educational settings is a heterocyclic one— the acetal formed by reaction of a diol with a cyclic ketone.

The common atom that connects the two (or sometimes three) rings is called the spiro atom.^[2]^: SP-0 In carbocyclic spiro compounds like spiro[5.5]undecane, the spiro-atom is a quaternary carbon, and as the -ane ending implies, these are the types of molecules to which the name spirane was first applied (though it is now used general of all spiro compounds).^[5]^: 1138ff The two rings sharing the spiro atom are most often different, although they can be identical [e.g., spiro[5.5]undecane and spiropentadiene, at right].^[3]^{: 319f.846f}

Selected spiro compounds
Elatol, isolated from Laurencia dendroidea (red algae)^[6]
Spironolactone, a commercial diuretic medication
Spiropentadiene, which is highly strained.^[7]
1-Bromo-3-chlorospiro[4.5]decan-7-ol, and '1-bromo-3-chlorospiro[3.6]decan-7-ol.

^ De Meijere, Armin; von Seebach, Malte; Zöllner, Stefan; Kozhushkov, Sergei I.; Belov, Vladimir N.; Boese, Roland; Haumann, Thomas; Benet-Buchholz, Jordi; Yufit, Dmitrii S.; Howard, Judith A. K. (2001). "Spirocyclopropanated Bicyclopropylidenes: Straightforward Preparation, Physical Properties, and Chemical Transformations". Chemistry - A European Journal. 7 (18): 4021–4034. doi:10.1002/1521-3765(20010917)7:18<4021::AID-CHEM4021>3.0.CO;2-E. PMID 11596945.
^ ^a ^b Cite error: The named reference IUPACspiros was invoked but never defined (see the help page).
^ ^a ^b ^c Clayden, Jonathan; Greeves, Nick; Warren, Stuart (2012). Organic Chemistry (2nd ed.). Oxford, UK: Oxford University Press. pp. 319f, 432, 604, 653, 746, 803, 839, 846f. ISBN 978-0-19-927029-3. Retrieved 2 February 2016.
^ For all four categories, see Reusch, William (1999). "Saturated Hydrocarbons, Alkanes and Cycloalkanes: Cycloalkanes (Table: Examples of Isomeric C₈H₁₄ Bicycloalkanes) or Nomenclature: Cycloalkanes (same Table), and passim". Virtual Text of Organic Chemistry (Jan. 2016 ed.). East Lansing, MI, USA: Michigan State University, Department of Chemistry. Retrieved 3 February 2016. The specific chapters can be found at [1] and [2], respectively, same access date. For the description featuring adjacent atoms for all but the isolated category, see Clayden, op. cit.
^ Cite error: The named reference ElielEtal94 was invoked but never defined (see the help page).
^ Smith, Laura K. & Baxendale, Ian R. (2015). "Total Syntheses of Natural Products Containing Spirocarbocycles". Org. Biomol. Chem. 13 (39): 9907–9933. doi:10.1039/C5OB01524C. PMID 26356301.
^ "Elusive bowtie pinned down". The Free Library. 13 July 1991. Retrieved 2 February 2016.

[1] De Meijere, Armin; von Seebach, Malte; Zöllner, Stefan; Kozhushkov, Sergei I.; Belov, Vladimir N.; Boese, Roland; Haumann, Thomas; Benet-Buchholz, Jordi; Yufit, Dmitrii S.; Howard, Judith A. K. (2001). "Spirocyclopropanated Bicyclopropylidenes: Straightforward Preparation, Physical Properties, and Chemical Transformations". Chemistry - A European Journal. 7 (18): 4021–4034. doi:10.1002/1521-3765(20010917)7:18<4021::AID-CHEM4021>3.0.CO;2-E. PMID 11596945.

[IUPACspiros-2] Cite error: The named reference IUPACspiros was invoked but never defined (see the help page).

[ClaydenOC12-3] Clayden, Jonathan; Greeves, Nick; Warren, Stuart (2012). Organic Chemistry (2nd ed.). Oxford, UK: Oxford University Press. pp. 319f, 432, 604, 653, 746, 803, 839, 846f. ISBN 978-0-19-927029-3. Retrieved 2 February 2016.

[Reusch-4] For all four categories, see Reusch, William (1999). "Saturated Hydrocarbons, Alkanes and Cycloalkanes: Cycloalkanes (Table: Examples of Isomeric C₈H₁₄ Bicycloalkanes) or Nomenclature: Cycloalkanes (same Table), and passim". Virtual Text of Organic Chemistry (Jan. 2016 ed.). East Lansing, MI, USA: Michigan State University, Department of Chemistry. Retrieved 3 February 2016. The specific chapters can be found at [1] and [2], respectively, same access date. For the description featuring adjacent atoms for all but the isolated category, see Clayden, op. cit.

[ElielEtal94-5] Cite error: The named reference ElielEtal94 was invoked but never defined (see the help page).

[SmithBaxendale15-6] Smith, Laura K. & Baxendale, Ian R. (2015). "Total Syntheses of Natural Products Containing Spirocarbocycles". Org. Biomol. Chem. 13 (39): 9907–9933. doi:10.1039/C5OB01524C. PMID 26356301.

[SciNews91-7] "Elusive bowtie pinned down". The Free Library. 13 July 1991. Retrieved 2 February 2016.

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