Butane, l-Bromo-3-methyl

There are two early examples in the literature where apparently an intermediately formed bisacceptor-substituted methylenecyclopropane was attacked by a nucleophile. 2-Bromo-3-(dicyanomethyl)pent-3-ene (22) was converted to (2,3-dimethylcyclopropylidene)malonodini-trile (23) in the presence of an excess of triethylamine in dichloromethane at room temperature. 23 could not be isolated but reacted further with 22 to give 6-ethylidene-l,2,5-trimethyl-spiro[2.4]heptane-4,4,7,7-tetracarbonitrile (24) in 70% yield.Also, treatment of 1-[bis(ethoxycarbonyl)methyl]-2,2-dimethylcyclopropanol or its precursor 3-chloro-3-methyl-butan-2-one with the sodium salt of diethyl malonate in tetrahydrofuran under reflux gave small amounts of adducts such as l,l-bis bis[(ethoxycarbonyl)methyl] -2,2-dimethylcyclo-propane and l-[bis(ethoxycarbonyl)methyl]-l-[(ethoxycarbonyl)methyl]-2,2-dimethyl-cyclopropane via dehydration and nucleophilic attack. ... 

Another situation in which the chemically robust nature of the 4-methyI-l, 2,4-triazole-3,5-dione adducts has been exploited is in the synthesis of bicyclobutane derivatives.Addition of 4-methyl-l,2,4-triazole-3,5-dione to bicyclo[1.1.0]butane gave the urazole 20, which was converted to 2,3-diazabicyclo[2.1.1]hex-2-ene and by thermolysis or photolysis back to bi-cyclo[1.1.0]butane. While this is not in itself a useful synthetic sequence, the urazole intermediates in such a sequence can be chemically modified in ways that would be impossible for the bicyclobutanes themselves. Hence for the adduct 21 of dimethyl bicyclo[1.1.0]butane-l,3-dicarboxylate, the ester groups can be modified into ethyl, vinyl, substituted vinyl, hydroxymethyl, bromo and other substituents and this was used to prepare, for example, 1,3-divinylbicyclo[1.1.0]butane (22) and l-ethyl-3-vinylbicyclo[1.1.0]butane. ... 

Dirhoda-bicyclo[1.1.0]butan 1,3-Bis-[f 5-cyClopentadienyl]-3-bromo-2,4-dioxo-l-methyl-XIII/9b, 429... 

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