Cubane-l,4-dicarboxylate

Dinitrocubane (28) has been synthesized by Eaton and co-workers via two routes both starting from cubane-l,4-dicarboxylic acid (25). The first of these routes uses diphenylphos-phoryl azide in the presence of a base and tert-butyl alcohol to effect direct conversion of the carboxylic acid (25) to the tert-butylcarbamate (26). Hydrolysis of (26) with mineral acid, followed by direct oxidation of the diamine (27) with m-CPBA, yields 1,4-diiutrocubane (28). Initial attempts to convert cubane-l,4-dicarboxylic acid (25) to 1,4-diaminocubane (27) via a Curtins rearrangement of the corresponding diacylazide (29) were abandoned due to the extremely explosive nature of the latter. However, subsequent experiments showed that treatment of the acid chloride of cubane-l,4-dicarboxylic acid with trimethylsilyl azide allows the formation of the diisocyanate (30) without prior isolation of the dangerous diacylazide (29) from solution. Oxidation of the diisocyanate (30) to 1,4-dinitrocubane (28) was achieved with dimethyldioxirane in wet acetone. Dimethyldioxirane is also reported to oxidize both the diamine (27) and its hydrochloride salt to 1,4-dinitrocubane (28) in excellent yield. ... 

Cubylcarboxonium ions have been also studied by Prakash, Olah, and co-workers.579,580 The parent cation 281 prepared under superacid conditions was stable at low temperature but decomposed to cubylacylium cation 282 as a result of further protonation and dehydration [Eq. (3.71)]. In addition to cation 281, di- and tetra-carboxonium ions and the corresponding protonated methyl esters were also observed as long-lived species stable under superacidic conditions. Experimental evidence and theoretical data indicated that the strained cubyl system effectively stabilizes the carbocationic centers through C—C bond hyperconjugation (283). On the basis of 13C data, three conformers of protonated dimethyl cubane-l,4-dicarboxylate (284-286) could be identified. 

Cubane- 1,2-dicarboxylic acid 12 (see Fig. 2.19), a precursor for 1,2-dihalocubanes was prepared from commercially available cubane-1,4-dicarboxylic acid in 65% yield. The other acids 14a and 14c were similarly prepared from the cubane-l,4-dicarboxylic acid 14b according to the literature procedures. 1H NMR spectra of the compound 13a showed a broad singlet at 4.41 for the clibyl protons, whereas compound 13b showed two multiplets. Conversion of bridgehead carboxylic acids to the corresponding halides using Pb(OAc)4 and iodine in refluxing benzene under illumination is reported. This is considered to be an alternative to Barton s method, because of its simplicity and ease of preparation, but it involves toxic lead compounds. 

Cubane-l,4-dicarboxylic acid rearranges to cuneane-2,6-dicarboxylic acid in a water-promoted transformation via the hydrogen cubane-l,4-dicarboxylate (Scheme 215). Solutions of tetrakis(guanidino)phosphazenium salts have been prepared. Unsaturated seven-membered lactams have been converted to fused pyrrolidinolac-tones by a process that involves the formation of an ammonium salt and subsequently a nitrogen ylide which initiates the rearrangement reaction. ... 

DPPA has been utilized in the synthesis of 1,4-dinitrocubane by Eaton and co-workers. Refluxing cubane-l,4-dicarboxylic acid with DPPA and Triethylamine in r-butanol forms the intermediate... 

Pentacyclo[4.2.0.02,5.03,8.04,7]octane-l,2-dicarboxylic acid (Cubane-l,2-dicarboxylic acid)... 

Crown-6 , see 1,4,7,10,13,16-Hexaoxacyclooctadecane, 3555 Crown ethers , see Cyclic poly(ethylene oxides), 0826 CS gas , see 2-Chlorobenzylidenemalononitrile, 3232b Cubane-l,2-dicarboxylic acid, see Pentacyclo[4.2.0.02 5.03,8.04,7]octane-1,2-dicarboxylic acid, 3255... 

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