Indene dibromide

Debromination. Ho and Wong have reported that some vic-dibromides are debrominated by this very hindered base (DMF, reflux) in surprisingly high yields. On the other hand, indene dibromide does not undergo this reaction. T.-L. Ho and C. M. Wong,Syn. Commun., 5, 87 (1975). 

Reaction fails with indene dibromide, however. 

This means that steric barriers exist which must be overcome to form an addition compound owing to nonplanarity of the nitro compound. The steric factor could also explain the fact that the addition compound reacts only slowly with bromine, whereas indene itself rapidly adds bromine to form a dibromide. 

Double dehydrobromination was also used in the preparation of 2-chloro-3a,7a-methanoindane (6). The dibromide, formed by brominating the corresponding monoalkene 5 at — 78 C, was treated with potassium ferr-butoxide in /ert-butyl alcohol, which gave 6 in 56% overall yield. Notably, this treatment left the chlorine atom intact. The chloride 6 served in turn as the starting material for the synthesis of 3a,7a-methano-l//-indene (see Section 5.2.2.1.1.3.)." ... 

Y = F) with sodiiun methoxide, but undergoes ring-opening with potassium hydroxide in t-butyl alcohol to give the acid o-C F4H-CF CF-C02H, whidi is converted into the dichloro-compound o-CsFaH-CFCl-CFCl-COaH by treatmmt with phosphorus pentachloride followed by hydrolysis. Both 3-chloroh tafluoro-and octafluoro-indene are converted into the oxo-sulphonic add (32) by 20% oleum, and the dibromide (33a) or the nitro-indane (33b) is formed when octa-fluoioindene reacts with bromine or HNOa-HF, respectively. The fomiation of the antiaromatic cabocation (34) when octafluoroindene dissolves in SbFs-SOa at -40°C has been briefly studied by n.m.r. spectroscopy. ... 

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