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IUPAC name
Other names
Bowtiediene; Spiropenta-1,4-diene
3D model (JSmol)
Molar mass 64.09 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Spiropentadiene, or bowtiediene, is a hydrocarbon with formula C5H4. The simplest spiro-connected cycloalkene, it is very unstable—decomposing even below −100 °C—due to its high bond strain and does not occur in nature. Its synthesis was reported in 1991.[1][2]


Spiropentadiene was synthesised from bistrimethylsilylpropynone 1 by reaction with p-toluenesulfonylhydrazide to tosylhydrazone 2 followed by treatment with sodium cyanoborohydride to allene 3 and followed by two successive reactions with chlorocarbene generated from methyllithium and dichloromethane to spiro compound 5. Spiropentadiene was trapped in a liquid nitrogen trap after reaction with TBAF in a double elimination reaction.

Spiropentadiene synthesis


The derivative dichlorospiropentadiene has been reported.[3] An all-silicon derivative (Si5 frame, (tBuMe2Si)3Si side groups) is also known.[4] In contrast to the carbon parent this compound is stable with a melting point of 216 to 218 °C. The angle between the two rings as measured by X-ray single-crystal analysis is 78°.


  1. ^ Billups, W. E.; Haley, M. M. (1991). "Spiropentadiene". Journal of the American Chemical Society. 113 (13): 5084. doi:10.1021/ja00013a067. 
  2. ^ Elusive bowtie pinned down - synthesis of spiropentadiene, a carbonaceous compound nicknamed bowtiediene because it is shaped like a bowtie, Science News, July 13, 1991.
  3. ^ Saini, R.; Litosh, V.; Daniels, A.; Billups, W. (1999). "Synthesis and characterization of 1,4-dichlorospiropentadiene". Tetrahedron Letters. 40 (34): 6157. doi:10.1016/S0040-4039(99)01293-9. 
  4. ^ Iwamoto, T.; Tamura, M.; Kabuto, C.; Kira, M. (2000). "A Stable Bicyclic Compound with Two Si&cjs0811;Si Double Bonds". Science. 290 (5491): 504–506. Bibcode:2000Sci...290..504I. PMID 11039928. doi:10.1126/science.290.5491.504.