Cyclopropane-1,1-dicarboxylates 2-substituted

The intermediacy of >/2-cyclopropene complexes of nickel has been proposed in catalyzed 2+1 reactions of free cyclopropene with electron-poor olefins, to give vinylcyclo-propanes. For example, the reaction of fumarate esters with 3,3-disubstituted cyclopropenes in the presence of Ni(COD)2 catalyst gave vinyl-substituted trans-2,3-cyclopropane dicarboxylate esters (equation 235)72 302. However, when maleic esters were used instead, a mixture of both cis and trans vinylcyclopropane diesters is obtained. 

Cyclopropanes substituted with a donor and an acceptor group underwent ring opening to form 2,3-dihydrofurans. For example, the (t-butyldiphenylsilyl)cyclopropane dicarboxylate depicted below was converted to the 2,3-dihydrofuran in 96% yield <01OL2717>. 

However, when the two substitutes are same as in cyclopropane 1, 2-dicarboxylic acid (xxiv), we will again have two geometrical isomers cis and trans, but because the molecule contains two similar chiral centres ( ), we will have (+) and (-) forms coming from the trans only along with its racemic variety. The cis form, having a (vertical) plane of symmetry will represent the mesovariety. Therefore, the condition is the same as in tartaric acid. 

Asymmetric synthesis of cyclopropanes, The reaction of dimethyloxosnifonium methylide with (E)-(2R,3S)-6-alkylidene-3,4-dimethyl-2-phenylperhydro-l,4-oxazepine-5,7-diones (1) yields cyclopropane derivatives (2) and dihydrofuranes (3). The ratio of the products depends on the solvent and temperature. Use of THF at 25° favors formation of 2, whereas formation of 3 is favored by use of DMF at -61°. The products (2 and 3) can be converted into optically pure cyclopropane-1,1-dicarboxylic acids (4) and 3-substituted y-butyrolactones (5), respectively. 

In contrast to the preceding intramolecular reactions, only a few intermolecular examples leading to bicyclo[l. 1. OJbutanes by carbene addition to cyclopropanes have been reported. Copper-catalyzed procedures generally require relatively high temperatures and yield mixtures of exo,exo-, endo.exo- and endo,endo- somtr% when 3-substituted cyclopropenes are used as reactants. Methyl 2,3-dipropylcycloprop-2-ene-l-carboxylate (8) provides the isomeric dimethyl l,3-dipropylbicyclo[1.1.0]butane-2,4-dicarboxylates (9) as a mixture (bp 90 100°C/0.5 Torr) that can be separated by preparative GC. The ejico,exo-isomer 9A is the major product. No yield is given. 

When Af-substituted imides of cyclopropane-c/j-l,2-dicarboxylic acid were reacted with sodium borohydride in methanol the product was the corresponding hydroxyamide in excellent yield, e.g. formation of 1. Similar primary reactions occurred on reaction of a derivative of cyclopropane-cH-l,2-dicarboxylic anhydride with bis(l,2-dimethylpropyl)borane (disiamylborane) in diethyl ether and also on reaction of 7/,A -disubstituted cyclopropanecar-boxamides with sodium bis(2-methoxyethoxy)aluminum hydride. ... 

Cyclopropane-1,1-dicarboxylic acid (30a) reacted with hydrobromic acid to (2-bro-moethyl)malonic acid (31a) . In a similar reaction, ethyl 1-acetylcyclopropane-l-carboxylate (31b) ( C enriched) was converted to 5-bromopentan-2-one upon treatment with hydrobromic acid and decarboxylation." In 2-benzoyl-3-phenylcyclopropane-1,1-dicarboxylic acid (31c), two different activating functions are present and can influence the addition of hydrogen bromide. In fact, products arising from the cleavage of either bond that link the phenyl-substituted carbon were isolated. Both primary products had lost hydrogen bromide and carbon dioxide. 

When diethyl tetracyanocyclopropane-l,l-dicarboxylate (6), a cyclopropane derivative with six electron-withdrawing groups, was treated with ammonia in diethyl ether, the reaction took an unforeseen course cleavage of the tetracyano-substituted bond occurred and one of the ester functions was eliminated to give a stabilized allyl anion 1 ... 

The selectivity for the alkene-substituted cycloadduct is also almost complete in the case of the reaction of l-methylene-2-(trimethylsilyl)cyclopropane (5) with dimethyl fumarate, which results in a 78% yield of dimethyl /ra x-4-(trimethylsilylmethylene)cyclopentane-l,2-di-carboxylate (7). Interestingly, only one of the stereoisomeric dimethyl 4-methylene-3-(trimethyl-silyl)cyclopentane-l,2-dicarboxylates [the (/ , / , / )-isomer 8] is formed selectively. ... 

Stereoselective synthesis of cydopropane-1,2-dicarboxylic acids or 1,2-dicyano substituted cyclopropanes by Michael addition (see also Hassner - Ghera - Little). 

Substitution of a cyclopropane by two geminal electron-withdrawing groups makes the three-membered ring very susceptible to nucleophilic attack. The readily-prepared phosphonium salt (480) condenses with the p-keto-ester anion (479) to furnish the cyclopentene (481). Similar nucleophilic attack on cyclopropane-l,l-dicarboxylic ester derivatives has been adapted to the synthesis of several prostaglandins. ... 

Scheme 1.23 Formal [3 + 3] cycloaddition of nitrones with 2-substituted cyclopropane-1,1-dicarboxylates.

The copper-catalysed 3 + 2-cycloaddition reactions of nitrones with alkynes leading to / -lactams have been extensively reviewed. The 3+2-cycloaddition reactions of dialkyl-substituted 2-benzylidenecyclopropane-l,l-dicarboxylates (54) and C-carbamoyl nitrones (53) produced simple isomeric spiro[cyclopropane-l,4-isoxazolidine] cycloadducts (55), which are readily transformed into isoxazolidine-fused / -lactams (56) in high yields (Scheme 15). BINOL-derived chiral phosphorami-date Au(l) catalysts have been used to catalyse the 3+2-cycloaddition of A(-allenyl amides with nitrones to produce chiral 4-alkylidenyl isoxazolidines in high yields and excellent enantioselectivity (up to 99% cc). The 3+2-cycloaddition of a-phenylnitroethene and (Z)-CA -diphenylnitrone in polar media (nitromethane and water) yielded 3,4-fra 5 -2,3,5-triphenyl-4-nitroisoxazolidine via a zwitterionic, two-step mechanism. ... 

---