Azodicarboxylic add

Heterodienophiles have also been studied diethyl azodicarboxylate adds across the 2,6-positions of a pyridazin-3-one, and singlet oxygen across the 2,5-positions of pyrazinones. The immediate cycloadduct is isolable when acryloyl cyanide is used as the heterodiene component in reaction with a pyrimidine-2,4-dione. ... 

Our approach is based on a reaction independently reported by two research groups (75-20). It has been found that azodicarboxylates add to vinyl ethers to provide [4+2] and/or [2+2] cycloadducts. They have shown that the [4+2] cycloaddition reaction is accelerated upon heating or irradiation at 350 nm, presumably due to a partial isomerization of the trans azo compound to the cis isomer, which would be more reactive. In principle, this reaction should be equally efficient with glycals, thereby allowing the introduction of an amino... 

Reference is made in Chapters 13 and 24 to the synthesis of /8-lactams by the addition of trichloroacetyl isocyanate to glycal derivatives followed by periodate cleavage of the sugar rings, and bis(trichloroethyl)azodicarboxylate adds to such compounds to afford a route to 2-amino-2-deoxyglycosides (Chapter 9). A novel cycloaddition reaction is illustrated in Scheme 6A. ... 

In an initial step triphenylphosphine adds to diethyl azodicarboxylate 5 to give the zwitterionic adduct 6, which is protonated by the carboxylic acid 2 to give intermediate salt 7. The alcohol reacts with 7 to the alkoxyphosphonium salt 8 and the hydrazine derivative 9, and is thus activated for a SN2-reaction ... 

Electron-rich aromatic compounds, such as phenol, anisole and A,./V-dimethylaniline, add to bis(2-trichloroethyl) azodicarboxylate under the influence of lithium perchlorate, boron trifluoride etherate or zinc chloride to yield para-substituted products 74, which are transformed into the anilines 75 by means of zinc and acetic acid86. Triflic acid (trifluoromethanesulphonic acid) catalyses the reactions of phenyl azide with benzene, toluene, chlorobenzene and naphthalene, to give TV-arylanilines (equation 34)87. 

Diethyl azodicarboxylate forms normal adducts with 2,3-dimethylbutadiene and with ethyl sorbate however, it is not a very good dienophile, presumably because it exists in the fraws-configuration. The sterically hindered diene 254 adds the ester to give mainly the ene product 255 (equation 137) and even cyclohexa-1,3-diene undergoes an analogous... 

Tetraalkoxylallenes give similar additions (72CB2437) and under forcing conditions tetrafluoroethylene (60JA852, 71JOU2361) and tetrafluorobutadiene (61JA386) add [2 + 2] to azodicarboxylates. 

Cyclobutadiene adds (79AJC2659) to azodicarboxylic acid to give fused diazetines (Scheme 5). 

Linear thieno[c J]benzothiadiazoles dimerize by linking at the carbocyclic peri positions <75ACR139>. While most [c] fused heterocycles add dienophiles across the heterocyclic ring, the thieno[l,2-c 4,5-c ]benzisothiazole (21) added ethyl azodicarboxylate across the benzenoid ring <86CB3158>. 

All the reactions described so far have mobilised six electrons, but other numbers are possible, notably a few [8 + 2] and [6 + 4] cycloadditions involving 10 electrons in the cyclic transition structure. A conjugated system of eight electrons would normally have the two ends of the conjugated system far apart, but there are a few molecules in which the two ends are held close enough to participate in cycloadditions to a double or triple bond. Thus, the tetraene 6.17 reacts with dimethyl azodicarboxylate 6.18 to give the [8 + 2] adduct 6.19, and tropone 6.20 adds as a 6-electron component to the 4-electron component cyclopentadiene to give the adduct 6.21. 

Enol Amination. The Cu[(S,5)-t-Bu-box] (OTf)2 complex was found to be optimal for promoting the enantioselective conjugated addition of enolsilanes to azodicarboxylate derivatives (eq 13). This methodology provides an enantioselective catalytic route to differentially protected ot-hydrazino carbonyl compounds. Isomerically pure enolsilanes of aryl ketones, acylpyrroles, and thioesters add to the azo-imide in greater than 95% ee. The use of an alcohol additive was critical to achieve catalyst turnover. Amination of cyclic enolsilanes was also possible. For example, the enolsilane of 2-methylindanone provides the adduct containing a tetrasubstituted stereogenic center in 96% ee and high yield. Acyclic (Z)-enolsilanes react in the presence of a protic additive with enantioselection up to 99%. ... 

Azodicarboxylates and related compounds have been widely used as dienophiles over the last six decades. A thorough description of these reactions is beyond the scope of this review. In a recent representative example of such a cycloaddition, Schmidt and coworkers found that diene (147) adds to diethyl azodicarboxylate to yield (148). This product was used in synthesis of aminoxylose derivative (149) (equation 59). 

A stmctural variation of azodicarboxylate is arenediazocyanide (151) prepared from the corresponding diazonium salt (equation 61)." Dienophiles of this class add regioselectively to 1,3-dienes in a Diels-Alder sense. This selectivity is consistent with both stepwise polar and concerted pericyclic mechanisms. 

Azodicarboxylic esters are excellent dienophiles and they can also add to electron-rich double bonds as heterodienes. Adducts of both types have been used as intermediates in the synthesis of amino sugars. 

Aromatic compounds add to DEAD (diethyl azodicarboxylate), in the presence of InCl3-Si02 and microwave irradiation, to give the A-aryldiamino compound [ ArNCCOaEO-NHCOaEt]. ... 

Other nitrogen compounds, among them hydroxylamine and hydroxylamines, " hydrazines, and amides (15-9), also add to alkenes. Azodicarboxylates (Boc-N= N-Boc) react with alkenes, in the presence of PhSiH3 and a cobalt catalyst, to give... 

In the first step of the Mitsunohu esterification the triphenylphosphine (74) adds to the weak N=N bond of diethyl azodicarboxylate (73) to give intermediate 75. 

The addition of diethyl azodicarboxylate to enol ethers gives diesters of 3-alkoxy-l,2-diazetidine-l,2-dicarboxylic adds. The reaction is stereospedfic, the energies of adivation are modest (29-46 kJ moF ) and the entropies of activation are negative (-36 to —46 J mol ). For n-butyl vinyl ether, the volume change of activation is very large... 

Dehydrooenation 1,4-Benzoquinone. Chloranil. o-Chloranil. Copper chromite. Copper-Chromium oxide. Diethyl azodicarboxylate. 2,3-Dichloro-3,6-dicyano-I,4-benzoquinone. DIphenylpIcrylhydrazyl, N-Lithioethylenediamlne. Mercuric acetate. Nickel catalyst. Oleic add, Palladium. Perbenmic acid. Potassium l-butoxide. Pyrldinium hydrobromide per-bramlda, Balinlum. Selenium dioxide. Sodium borohydride. Sulfdr (sm 1,2-Naphthalic anhydridli preparation). Tetracyanoethylene. Thionyl chloride. Trityl perchlorate. 

The tetraphenyl ester of azodiphosphonic add is a more reactive dienophile than diethyl azodicarboxylate. Because of its instability it is prepared from... 

Ethyl azodicarboxylate can be prepared by treating ethyl hydrazodicarboxylate with concentrated nitric add2 or a mixture of concentrated and fuming nitric add.4-5... 

The product of the cyciization of hydrazones under nitrosating conditions (as described in Section 1.3) is a triazine (rather than a triazole) when the hydrazone is derived from a benzaldehyde instead of an acetophenone [2793]. A mixture of nitrous and acetic acids also gives a triazine [2247, 2646]. Further variations in the product are possible by varying the nitrosating reagent when diethyl azodicarboxylate-acetic acid-nitrous add is used, triazine-4-oxides are formed [2247, 2849]. Recent work on polyazines has been reviewed [3985]. 

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