9, 11-Dihydro annulene derivative

At the beginning of the 70s Beck and co-workers discovered the electrocatalytic activity of dihydro-dibenzo-tetra-aza-annulene 8>12>, and Binder, Sandstede and co-workers that of tetraphenylporphyrine and its tetramethoxy derivative 9,13-15). 

The dihydro-derivative (58) of the unique sesquiterpenoid spiniferin-1 (57), which incorporates the novel l,6-methano[10]annulene skeleton, has been synthesized (Scheme 4) and this confirms beyond doubt its precise structure. ... 

Youngs and Tessier synthesized one of the few [2,l-c]lF derivatives not already discussed [96]. Treatment of tribenzocyclotriyne 176 with 4 equiv. n-BuLi collapsed the annulene core to furnish the [2,l-c]lF dianion 177 subsequent quenching with MeOH as the proton source afforded the benzo-fused dihydro-lF 178 (Scheme 49). 

In the dioxido system, a bridge flipping of the dihydro precursors, 41 42b, was accomplished by heating at 80—100°C for about forty hours. In the present case, synthesis of the < f -l,6-methano-8,13-oxido-[14]annulene has not been possible, because the aw i-dihydro precursor, presumably as the open form 45 a, (c.f. 41), as derived from the anti-tetrabromide, isomerizes spontaneously to the syn compound 45 b at room temperature 159). Consequently, sy -l,6-methano-8,13-oxido-[14]-annulene, 39, is the ultimate product from the anti precursors. 

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