Diethyl fumarate, addition

IPreparation of 2-trimethylsilyloxybuta-l,3-diene and Diels-Alder addition Iwith diethyl fumarate. 

The common by-products obtained in the transition-metal catalyzed reactions are the formal carbene dimers, diethyl maleate and diethyl fumarate. In accordance with the assumption that they owe their formation to the competition of olefin and excess diazo ester for an intermediate metal carbene, they can be widely suppressed by keeping the actual concentration of diazo compound as low as possible. Usually, one attempts to verify this condition by slow addition of the diazo compound to an excess (usually five- to tenfold) of olefin. This means that the addition rate will be crucial for the yields of cyclopropanes and carbene dimers. For example, Rh6(CO)16-catalyzed cyclopropanation of -butyl vinyl ether with ethyl diazoacetate proceeds in 69% yield when EDA is added during 30 minutes, but it increases to 87 % for a 6 h period. For styrene, the same differences were observed 65). 

EvenPd(OAc)2 is not effective in catalyzing the cyclopropanation of a,P-unsaturated nitriles by ethyl diazoacetate. Instead, vinyloxazoles 92 are formed from acrylonitrile or methacrylonitrile by carbenoid addition to the CsN bond 143 Diethyl maleate and diethyl fumarate as well as polyketocarbenes are by-products in these reactions the 2-pyrazoline which would result from initial [3 + 2] cycloaddition at the C=C bond and which is the sole product of the uncatalyzed reaction at room temperature, can be avoided completely by very slow addition of the diazoester... 

Another example of type iii-a is the trifluoromethylation of double bonds by electrolysis of trifluoroacetic acid in the presence of olefins. Methyl vinyl ketone, vinyl acetate, diethyl fumarate, diethyl maleate, Ai-ethylmaleimide, and 2,5-dihydrothiophene-l,1-dioxide were examined as olefins. The products were bis-trifluoromethylated additive dimers (66) (type iii-a) and monomers (67) (type... 

Diisobutylalane (diisobutylaluminum hydride) (0.85 mol) is added under nitrogen over a period of 10 hours to a stirred solution of 34.4 g (0.2 mol) of diethyl fumarate in 160 ml of benzene. The temperature rises to 50°. After standing overnight at room temperature, the reaction mixture is decomposed by the addition of 76.8 g (2.4 mol) of methanol in 150 ml of benzene followed by... 

Addition of electron-poor alkenes such as /ran -stilbene, diethyl fumarate and maleate, and fumaronitrile to (50) do not cause nitrogen evolution. Even on heating cycloaddition products were not isolated, although decomposition was induced. Addition of bases such as benzylamine had no influence on the decomposition rate <78JCS(P1)1440>. 

Typically the addition of the mesomeric anion (12) to the a, / -unsaturated ester, diethyl fumarate, proceeds in a 1,4-manner (the Michael reaction or Michael addition). 

As a model study of methyl cobalamine (methyl transfer) in living bodies, a methyl radical, generated by the reduction of the /s(dimethylglyoximato)(pyridine)Co3+ complex to its Co1+ complex, reacts on the sulfur atom of thiolester via SH2 to generate an acyl radical and methyl sulfide. The formed methyl radical can be trapped by TEMPO or activated olefins [8-13]. As a radical character of real vitamin B12, the addition of zinc to a mixture of alkyl bromide (5) and dimethyl fumarate in the presence of real vitamin B12 at room temperature provides a C-C bonded product (6), through the initial reduction of Co3+ to Co1+ by zinc, reaction of Co1+ with alkyl bromide to form R-Co bond, its homolytic bond cleavage to form an alkyl radical, and finally the addition of the alkyl radical to diethyl fumarate, as shown in eq. 11.4 [14]. 

The C—X reduction potentials of allylic halides and unsaturated a-haloesters are similar, and vary depending on their substitution pattern. The regioselectivity of the addition, therefore, is also influenced by the relative reduction potentials. l-Chloro-3-methyl-2-butene (41) reacts with diethyl fumarate (42) through attack from the primary carbon (equation 31), whereas with methyl crotonate (44) allylation takes place at the more highly substituted tertiary carbon (equation 32). 

Diethyl malonate adds to diethyl fumarate in a conjugate addition reaction promoted by sodium ethoxide in dry ethanol to give a tetraester, Diethyl fumarate is an excellent Michael acceptor because two ester groups withdraw electrons from the alkene, The mechanism involves deprotonation of the malonate, conjugate addition, and reprotonation of the product enolate by ethanol solvent, In this reaction two ester groups stabilize the enolate and two more promote conjugate addition. 

The present synthesis is an adaptation of a previously reported synthesis4 in a divided cell (i.e., separate anode and cathode compartments). The overriding consideration in making this modification has been to simplify the operations involved and render the synthesis more attractive to chemists not well acquainted with electrochemical procedures. The main simplification achieved is that the pH is controlled internally via the anodic generation of protons as noted above (in the reported procedure4 this is achieved by periodic addition of acetic acid to the cathode compartment). A further simplification has been to run the reaction with a constant current rather than at controlled cathode potential. After the electrolysis has been initiated, the reaction requires no special attention. A small price is paid for the simplicity of the present synthesis in that the yield is somewhat lower than that obtained previously.4 The major by-product formed is diethyl succinate, which results from a 2e reduction of diethyl fumarate or diethyl maleate ... 

The addition of elemental fluorine to diethyl fumarate in dichlorodifluoromethane at — 40"C yields diethyl 2,3-difluorosuccinatc... 

Organometallic reagents react with olefinic esters by both 1,2 and 1,4 addition. The latter process leads to saturated esters and is exhibited by diethyl fumarate and to a greater extent by ethylenetetracarboxylic ester, (CjH50jC)jC = C(C0jCjH5)j. These substances are starting materials for the synthesis of alkyl- and aryl-substituted succinic esters. ... 

Interestingly, bicyclopropylidene (7) also reacts with selected electron-deficient open-chain al-kenes, e.g. diethyl fumarate. When tris(2-phenylphenyl) phosphite is employed to modify the nickel catalyst, the yield of the [2 + 2] cycloadduct 10 amounts to 34% and the [3 + 2] cycloadduct 11 is formed as a minor product. Additionally, two diastereomers of the double [3 + 2] cyclo-adduct 12, formally arising from 7 by proximal cleavage of one cyclopropane ring and distal cleavage of the other, are formed in 15.6% yield. ... 

The copper-catalyzed decomposition of ethyl diazoacetate in the presence of a ketene acetal also leads to the corresponding cyclopropane in addition to larger quantities of diethyl maleate and diethyl fumarate ]f p-unsubstituted or... 

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