✍ Scribed by Ronald Breslow; David A. Cortés; Bernhart Jaun; R. David Mitchell
No coin nor oath required. For personal study only.
Chlorination of tricyanocyclopropane is observed to lead directly to tnchlorotricyanocyclopropane which undergoes a remarkable reductive conversion to hexacyanobenzene. The synthesis of mono-and dichlorotricyanocyclopropane (4 and 5) and their use as potential precursors for tricyanocyclopropenyl anion is described: The cyclopropenyl anion is the simplest antiaromatic system. The parent compound is terribly unstable, and trialkyl or triphenyl derivatives are also so unstable that they have only been transient species produced by electrochemical re-ducti0n.l However, one might hope that with good stabilizing groups the cyclopropenyl anion system could be isolable. For instance, our estimate of the acidity of triphenylcyclopropene indicates that its pK, is approximately 20 units higher than the pKa of triphenylmethane.2 If this difference were paralleled for cyano substituents, the very low pK, of tricyanomethane suggests that tricyanopropene could have a pK, near 20 and thus 1 could be reasonably stable. Similar arguments can be made for other strongly stabilizing substituents.
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