Electron-deficient double

The TT-allylpalladium complexes 241 formed from the ally carbonates 240 bearing an anion-stabilizing EWG are converted into the Pd complexes of TMM (trimethylenemethane) as reactive, dipolar intermediates 242 by intramolecular deprotonation with the alkoxide anion, and undergo [3 + 2] cycloaddition to give five-membered ring compounds 244 by Michael addition to an electron-deficient double bond and subsequent intramolecular allylation of the generated carbanion 243. This cycloaddition proceeds under neutral conditions, yielding the functionalized methylenecyclopentanes 244[148], The syn-... 

Acrylamide, C H NO, is an interesting difiinctional monomer containing a reactive electron-deficient double bond and an amide group, and it undergoes reactions typical of those two functionalities. It exhibits both weak acidic and basic properties. The electron withdrawing carboxamide group activates the double bond, which consequendy reacts readily with nucleophilic reagents, eg, by addition. 

This synthesis is only one example of a wide range of reactions which involve aryl (or alkyl) radical addition to electron-deficient double bonds resulting in reduction.The corresponding oxidative reaction using aryl radicals is the well known Meerwein reaction, which uses copper(II) salts. 

A more efficient agent than peroxy compounds for the epoxidation of fluoro-olefins with nonfluonnated double bond is the hypofluorous acid-acetomtrile complex [22] Perfluoroalkylethenes react with this agent at room temperature within 2-3 h with moderate yields (equation 13), whereas olefins with strongly electron-deficient double bond or electron-poor, sterically hindered olefins, for example l,2-bis(perfluorobutyl)ethene and perfluoro-(l-alkylethyl)ethenes, are practically inert [22] Epoxidation of a mixture of 3 perfluoroalkyl-1-propenes at 0 C IS finished after 10 mm in 80% yield [22] The trifluorovinyl group in partially fluorinated dienes is not affected by this agent [22] (equation 13)... 

An example of the efficient formation of an electron-deficient double bond by RCM was disclosed by a Japanese group in a novel total synthesis of the macrosphelides A (209) and B (208) (Scheme 41) [100]. When the PMB-pro-tected compound 204 was examined as a metathesis substrate, the ring closure did not proceed at all in dichloromethane using catalysts A or C. When the reaction was carried out using equimolar amounts of catalyst C in refluxing 1,2-dichloroethane, the cyclized product 205 was obtained in 65% yield after 5 days. On the other hand, the free allylic alcohol 206 reacted smoothly at room temperature leading to the desired macrocycle 207 in improved yield. 

In the presence of Bu OK, (benzotriazole-l-yl)methyl isocyanide (BetMIC) 697 undergoes alkylation on the methylene group to give isocyanide 698. The anion derived from 698, upon its treatment with Bu OK, adds to the electron-deficient double bonds of ajl-unsaturated ketones, esters or nitriles to produce pyrroles 699. A similar reaction of isocyanide 698 with Schiff bases provides imidazoles 700. In both cases, use of unsubstituted isonitriles 697 in the reactions leads to heterocycles 699 and 700 with R1 = H (Scheme 108) <1997H(44)67>. 

At the cathode, olefins with electron deficient double bonds can be hydrodimer-ized (Eq. 1). This reaction has been developed for acrylonitrile [22] in a technical adipodinitrile synthesis [23] with a scale of more than 300.000 tons per year. The scope of this hydrodimerization has been substantiated with many examples [24-33]. 

The epoxidation occurs at electron deficient double bonds, thus it is only the double bond adjacent to a ketone functionality that is epoxidised. This phenomenon allows scope for further elaboration of our substrates, hence several transformations have been investigated in order to diversify the nature of the products. Indeed, substrates used in the epoxidation reaction intentionally featured several functionalities which could each be modified selectively dependent upon the reaction conditions employed. Such reactions include ... 

As described in equation 78, the relatively electron-rich ring double bond of a- or fi-ionone was regioselectively epoxidized, whereas the electron-deficient double bond was not oxidized at all. This result also supports the radical rather than the anionic character of 52. 

The basic amino group of the 1-position in semicarbazide or thiosemi-carbazide may be used to react by a substitution reaction with activated halides [52], ethers [51], hydroxy [53], phenoxy [54], and amino groups [55] to yield substituted 1-semicarbazides or thiosemicarbazides. In addition, the amino group of the 1-position may add to electron-deficient double bonds [56]. Formaldehyde and other aldehydes may add to all the available free NH groups to give methylol, alkylol, or polymeric products under basic conditions [57]. Aldehydes or ketenes usually give semicarbazone derivatives, and these in turn are used analytically to identify the purity or structure of a known aldehyde [3]. 

Various mono- or di-olefins were oxidized regioselectively to their epoxides in high yield with the 2-nitrobenzenesulfonylperoxy intermediate 51 generated in situ from 2-nitrobenzenesulfonyl chloride and KO2 at —35 °C in CH3CN (equation 78)226. Thus /J-ionone was oxidized using 51 to the corresponding mono epoxide product in high yield (83%). That the electron-deficient double bonds remain intact under the reaction conditions shows the electrophilic character of 51. 

The maleimide group can undergo a variety of chemical reactions. The reactivity of the double bond is a consequence of the electron withdrawing nature of the two adjacent carbonyl groups which create a very electron-deficient double bond, and therefore is susceptible to homo- and copolymerizations. Such polymerizations may be induced by free radicals or anions. Nucleophiles such as primary and secondary amines, phenates, thiophenates, carboxylates, etc. may react via the classical Michael addition mechanism. The maleimide group furthermore is a very reactive dienophile and can therefore be employed in a variety of Diels Alder reactions. Bisdienes such as divinylbenzene, bis(vinylbenzyl) compounds, bis(propenylphenoxy) compounds and bis(benzocyclobutenes) are very attractive Diels Alder comonomers and therefore some are used as constituents for BMI resin formulations. An important chemical reaction of the maleimide group is the ENE reaction with allylphenyl compounds. The most attractive comonomer of this family is DABA particularly when tough bismaleimide resins are desired. 

Fluorinated carbocations play an important role as intermediates in electrophilic reactions of unsaturated compounds, although the highly electron-deficient double bond in fluoroalkenes is not usually susceptible to electrophilic attack. Only the most powerful electrophilic reagents... 

The photocycloaddition of aliphatic ketones to the electron-deficient double bonds of frans-l,2-dicyanoethylene282,283 and maleic anhydride 282 [Eq. (72)] is believed to proceed by an alternative mechanism involving nucleophilic attack on the double bond by the n, ir singlet state of the carbonyl,... 

Additions of nucleophiles to electron-deficient double bonds, e.g. the classical Michael addition or the Cu -mediated 1,4-addition of Grignard reagents to a,3-unsaturated carbonyl compounds (see previous... 

Most of the reactions which will be discussed lead to carbonyl compounds with a stereogenic center in the 3-position. This is illustrated in Scheme 1 a substrate molecule (1 X = heteroatom or heteroatom-based functional group), having an electron-deficient double bond, is attacked by a nucleophilic reagent (possibly in the presence of a coordinating ligand or a catalyst) to form an anionic intermediate (2), which is then converted to the product (3) on hydrolytic work-up. 

Control of the selectivity of the addition often is best achieved by choosing the proper reactants. The major influence is steric. The organic portion of the organopalladium intermediate normally adds to the less-hindered, double-bond carbon of the olefin. The secondary electronic effect is to cause the organic group to add to the more electron-deficient double-bond carbon. The structure of the vinylic halide also may influence the selectivity of the addition. Both vinyl bromide and 2-bromopropene (and other internal vinylic halides) add... 

Step-growth polymerization can be performed by reaction of diamine or dithiol on bismaleimide (Fig. 9). The reaction is a nucleophilic attack on the electron-deficient double bond activated by the two electron-withdrawing adjacent carbonyl groups. 

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