Spiropentadiene, or bowtiediene, is a hydrocarbon with formula . The simplest Spiro compound-connected diene, it is very unstable—decomposing even below −100 °C—due to its high angle strain and does not occur in nature. Its synthesis was reported in 1991.
Synthesis
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.
Derivatives
The derivative dichlorospiropentadiene has been reported.
An all-
silicon derivative (Si
5 frame, (
tBuMe
2Si)
3Si side groups) is also known.
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°.
