Alkenes reaction with tetracyanoethylene

Although methylenecyclopropanes are highly strained molecules, they are stable at ambient temperature. At elevated temperature they undergo [2 + 2]-type reaction with alkenes such as butadiene and maleic anhydride and [3 + 2] reaction with tetracyanoethylene. The latter reaction involves a trimethyl-enemethane diradical intermediate. For catalytic transformations of methylenecyclopropanes, nickel(O) and palladium(O) complexes have been used successfully. 

Alkenes with electron-withdrawing groups may form cyclobutanes with alkenes containing electron-donating groups. The enamine reactions, mentioned above, are examples of this, but it has also been accomplished with tetracyanoethylene and similar molecules, which give substituted cyclobutanes when treated with alkenes of the form C=C—A, where A may be... 

The distinction between electrophilic and electron-transfer mechanisms of addition reactions to vinyl double bonds of ArX—CH=CH2 (X = S, O, Se) has been achieved by studying substituent effects. Specifically, the effects of meta and para substituents on the rates of electrophilic additions correlated with Hammett radical cations correlates with statistical tests. The ofclcctrophilicj/o-1 (FT) dichotomy is in accord with the conventional paradigm for cr/cr+ correlations and further support has been found by ah initio calculations. Interestingly, the application of this criterion to the reactions of aryl vinyl sulfides and ethers with tetracyanoethylene indicates that cyclobutanes are formed via direct electrophilic addition to the electron-rich alkene rather than via an electron-transfer mechanism.12... 

IOB alone epoxidizes some electron-deficient alkenes, in a reaction where its oxygen attacks the substrate nucleophilically. An example of this type was with tetracyanoethylene which was converted into its epoxide (74%) similarly, ketenes formed unstable a-lactones which polymerized [7],... 

This substrate, along with the corresponding substrate 6, which has a cyclo-butanation rate of 1.2 x 10 , have been proposed as sensitive cation radical probes, for detecting the presence of cation radical intermediates in various reactions [74]. An interesting example is the reaction of tetracyanoethylene (TCNE) with electron rich alkenes, a reaction for which an electron transfer mechanism had been considered (Scheme 39) [75],... 

Abdel-Galil et al. (88BSF658) (Scheme 137) reported that heating pyrazol-3-one 62 with tetracyanoethylene in ethanol gave 2-(3-oxopyrazol-4-yl)-2-(pyrazol-4-yl)-malononitrile 449. The reaction initially gives intermediate 447 followed by conjugative addition of a second molecule of pyrazol-3-one 62 to the exocyclic alkene bond of 447 that leads to addition product 448, which then tautomerises to stable product 449. 

Applications of tetracyanoethylene have been reviewed recent information on molecular complexes, ozonization of alkenes and alkynes (the Criegee reaction), and reactions with ketones is included. Dicyanoketene has been prepared in situ from 2,5-diazido-3,6-dicyano- and 2,6-diazido-3,5-dicyano-l,... 

New Applications of Tetracyanoethylene (TCNE) in Organic Chemistry, A. J. Fatiadi (1986). This review with 501 references deals with reactions of tetracyanoethylene used in organic synthesis. Information on molecular complexes, ozonization of alkenes and acetylenes, dehydrogenation and tricyanovinylation, reactions of TCNE oxide, reactions with ketones and diketones, synthesis of heterocycles and cationic polymerizations are included in this survey. Some industrial and analytical applications are also discussed. 

As previously shown in equation (52), the Rh -peroxo complex (69) selectively oxidizes terminal alkenes with methyl ketones. In contrast, the complex [Rh02(dppe)2] C104 was found to be inactive, illustrating that it is necessary to to be able to create a coordination site for the alkene at rhodium. Further, an Rh peroxometallacycle (76) from the reaction of (69) with tetracyanoethylene has been characterized. ... 

The reaction is inhibited by added water. The formation of such a metal-locyclic intermediate resembles the isolation of such compounds from the reaction of Pt02(PPh3)2 with electron-deficient alkenes such as tetracyanoethylene [33] ... 

The nickel compounds NiRa(bipy) react with a variety of alkenes, including ethylene, norbomadiene, maleic anhydride, and tetracyanoethylene, to produce Ni(bipy)(alkene) or Ni(bipy)(alkene)2. A kinetic study, supported by characterization of intermediates from the reactions with aorolein and with acrylonitrile, indicates that the reaction mechanism involves the intermediacy of transient complexes NiR2(bipyXalkene), containing the alkene TT-bonded to the nickel as in the products. There is a correlation between the rates of these reactions and the stabilities of the respective complexes Ni(bipy)(alkene). The unstable species CoH(LL)2, where LL = bipy or phen, undergo substitution reactions with, for example, carbon monoxide, in which one LL ligand is replaced. One LL can also be replaced by alkyl halides here the reaction is oxidative elimination rather than simple substitution. ... 

Alkenes of all types can be converted to cyclopropane derivatives by this reaction (though difficulty may be encountered with sterically hindered ones). Even tetracyanoethylene, which responds very poorly to electrophilic attack, gives cyclopropane derivatives with carbenes.Conjugated dienes give 1,2 addition ... 

When other acceptor systems such as tetracyanoethylene, ethyl propiolate, dibenzoylacetylene, or dimethyl azodicarboxylate were reacted with 41, no additional products were formed. Accordingly, the scope of the reaction for the nucleophilic addition of 41 to electron-poor alkenes, alkynes, and diazo compounds is quite narrow. 

Cycloadduct formation is not observed upon irradiation of t-1 with fumaronitrile, maleic anhydride, or tetracyanoethylene. Irradiation of t-1 and maleic anhydride results in the formation of an alternating copolymer (96). The radical-ion pair or free radical ions obtained upon irradiation of the charge-transfer complex in polar solvent are presumed to be the initiating species. Irradiation of the ground state complex of t-1 and tetracyanoethylene at 580 nm in solution or the solid state results in neither adduct formation or t-1 isomerization (76). Irradiation of t-1 at 313 nm in the presence of tetracyanoethylene results in rapid isomerization followed by slow but quantitative formation of phenanthrene and tetracyanoethane (97). Product formation is proposed to occur via a dark reaction of dihydrophenanthrene with the electron-poor alkene. 

Linn and Benson discovered in 1963 the ability of tetracyanoethylene oxide (145) to react with alkenes and alkynes at elevated temperatures in [3 + 2] cycloadditions.139 The kinetics of the reaction of (145) with styrene revealed that the formation of (147) is preceded by a first-order step consisting of the electrocyclic ring opening to the carbonyl ylide (146 Scheme 33). 

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