Spiro-antiaromatic

Using a diagram adapted from that in Fig. 1.41, show that the spirononat-etraene 1.31 is spiro-antiaromatic. 

In contrast to the above, 4n systems arc spiro-antiaromatic. This is easily shown by constructing the diagram (Figure 12.13) for spiro-nonatctraenc. Compared to... 

An excellent example of spiroantiaromaticity is spiro [4.4] nonatetraene. Please explain how antiaromaticity comes into the picture. 

In contrast, a handful of successful studies describing DA reactions of [4]radi-alenes have been disclosed [58-61]. Although only single additions are known, in theory multiple additions are possible. Consider, for example, the DA reactions of [4]radialene (175) and ethylene (Scheme 12.37). The first reaction, at any of the 4 equivalent diene sites, affords cyclobutene 176. If a second DA reaction were to occur, the antiaromatic cyclobutadiene 177 would be generated. Although this class of compounds is reported to be highly unstable, the compounds are not inaccessible [62,63]. Cyclobutadiene 177 carries a diene locked in the s-cis conformation that could react in a third DA reaction to yield the spiro-fused tetracycle 178, a reaction that is not without precedence [62, 63]. 

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