Kleine Ringe, 74. Hexa‐<i>tert</i>‐butyl‐3,3′‐bicyclopropenyl

Abstract

Small Rings, 74 [1] . ‐ Hexa‐ tert ‐butyl‐3,3′‐bicyclopropenyl Title compound 3 can be prepared by reductive coupling of tri‐ tert ‐butylcyclopropenylium tetrafluoroborate ( 4a ) with lithium. Upon treatment with AgBF 4 3 does not undergo valence isomerization to the Dewar form of hexa‐ tert ‐butylbenzene ( 2 ) but is reoxidized under backformation of substrate 4a . The photochemical behavior of 6 is also unusual: Irradiation at room temperature results in gas evolution. However, instead of 7 , the s̀‐diketone 5 is isolated. Monoketone 7 is only formed if 6 is irradiated in an organic matrix at ‐196°C.