Azodicarboxylate cyclic

The reaction of morpholine enamines of cyclic ketones with ethyl azodicarboxylate has also been demonstrated 56,136). The enamine (113) on reaction with ethyl azodicarboxylate can give the 2- or 2,6-bis(N,N di-carboxyhydrazino)cyclohexanones 199 and 200, respectively, on hydrolysis. 

The use of azodicarboxylates as a route to dioxaphosphoranes continues to attract attention. In the most recent contribution, triphenylphosphine and di-iso-propyl azodicarboxylate (43) are shown to react with prcpane-1,3-diol and butane-1,4-diol in THF at 0°C under high dilution conditions to give the expected six-and seven-membered-ring phosphoranes (44 ab)36. In more concentrated solution however, cyclic oligomers are formed. Substituted and ccnformationally restricted 1,3- and 1,4-diols form the expected cyclic phosphoranes without recourse to high dilution techniques. 

Pavan Kumar et al. <2006NJC717> investigated the reaction of diethyl azodicarboxylate (DEAD) or diisopropyl azodicarboxylate (DIAD) with cyclic phosphates or phosphoramides in order to determine the structural preferences in spirocyclic penta- and hexacoordinate aminophosphoranes. They found that sulfur would coordinate to phosphorus to form the [3.3.0] bicyclic compounds 94-96. 

Virtually all bicyclic azoalkanes are made via this route from cyclic 1,3-dienes. (For a recent review on azoalkanes, see Ref. 191.) Azodicarboxylic... 

The reactivity of compound 113 toward reactive linear and cyclic dienophiles was reported in a study directed to find a model systems for the proposed [4+2] cycloaddition in the biosynthesis of the natural products brevianamides, paraherquamides, and marcfortines. With DMAD and diethyl azodicarboxylate the formation of 114 and 115 was almost quantitative after 48 h at 80 °C (Cbz = Carbobenzyloxygroup). When relatively unreactive dienophiles such as cyclopentene and cyclohexene were used, harsh reaction conditions and/or a Lewis acid catalyst are necessary for the formation of 116a and 116b (Scheme 16). In contrast, the analogous intramolecular reaction carried out on compound 117 takes place within a few hours at room temperature, even in the absence of a Lewis acid catalyst, to give 118 in 42% yield (Scheme 16) <2000T6345>. 

Treatment of the cyclic ketene aminal 267 with diethyl azodicarboxylate results in formation of the reduced ring system 268 (Equation 52), probably via an initial aza-ene reaction, followed by fragmentation and ring closure <2002T7791>. 

Attack on Nitrogen. A variety of cyclic derivatives of phosphorous acid have been converted into spirophosphoranes (51), using diethyl azodicarboxylate as the condensing agent,42 probably by initial addition to nitrogen to give (50). Several... 

The chemistry of chiral 1,3-dithiane 1-oxides, in particular their use as chiral auxiliaries, has been reviewed <19980PP145>. Some further developments in this field are the stereoselective a-alkylation with alkyl halides <1997T13149> or a-hydrazination with di-fert-butyl azodicarboxylate (DBAD) <2000T9683>. The carbonyl group of 2-acyl-l,3-dithiane 1-oxides was also used as an electrophile (Scheme 82). Interestingly, acyclic enolates react with these substrates to give a 95 5 mixture of anti- and ry -adduct, whereas cyclic enolates produce a mixture of anti- and ry -adduct in 8 92 ratio <2000JOC6027>. 

We were not able to obtain any cycloadduct from unactivated 2-azadienes 139 and esters of acetylenedicarboxylic acid. However, we found that 139 did cycloadd to typical electron-poor dienophiles such as esters of azodicarboxylic acid and tetracyanoethylene (Scheme 62). Thus, diethyl and diisopropyl azodicarboxylates underwent a concerted [4 + 2] cycloaddition with 139 to afford in a stereoselective manner triazines 278 in 85-90% yield (86CC1179). The minor reaction-rate variations observed with the solvent polarity excluded zwitterionic intermediates on the other hand, AS was calculated to be 48.1 cal K 1 mol-1 in CC14, a value which is in the range of a concerted [4 + 2] cycloaddition. Azadienes 139 again reacted at room temperature with the cyclic azo derivative 4-phenyl-1,2,4-triazoline-3,5-dione, leading stereoselectively to bicyclic derivatives 279... 

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. 

Both cyclic and acyclic R-N = N — R systems undergo ene reactions with simple alkenes, and most studies have employed either A -substituted triazolinediones 1 or azodicarboxylate diesters 3 to produce the triazolidines 2 and the hydrazines 4, respectively. 

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%. ... 

The catalyst 6 forms an imminium species (not shown) via a nucleophilic attack of the Lewis basic amine at the carbonyl moiety of substrate 7. The imminium ion is deprotonated to give enamine 8. Coordination of the electrophile 9, which can be an aldehyde, ketone or azodicarboxylate, leads to the transition state 10. In this way, the facial orientation of the substrates is more or less fixed in a cyclic conformation, depending on the steric- and electronic properties of the constellation. The electron-donating properties of the nitrogen atom then directs the addition to the electrophile that is saturated by the Bronsted acid, in this case the carboxylic acidic proton. 

Reagents formed by combining PhjP with CCU and with diethyl azodicarboxylate (DEAD) promote cyclization of amino alcohols to cyclic amines (Scheme 26). Various 2-amino alcohols reacted with diethoxytriphenylphosphorane (66) to afford the corresponding aziridines in 85-90% yields. The reaction proceeds with retention of the configuration at the amino carbon (C-2) (Scheme 26). In view of... 

Mixed substituted orthoesters, e.g. (383 equation 180), can be obtained by addition of alcohols to ketene 0,0-acetals. With the aid of phosphoranes containing a ketene O,(7-acetal structure, various orthoesters, e.g. (384) and (385) (Scheme 70) were prepared. " Cyclic orthoesters (386)-(390) (Scheme 71) are formed in cycloaddition reactions of ketene 0,0-acetals with aldehydes, ketones, 7.848 gj.yj cyanides, oxiranes, a-keto esters, o-diketones or ketones (with irradiation), a,3-unsaturated aldehydes and ketones (under pressure or catalyzed by ZnCh), diazoaceto-phenone, 7 diazoacetone and azodicarboxylate. ... 

Catalytic asymmetric construction of nitrogen-substituted quaternary stereocenter has been another important and challenging task in asymmetric synthesis. The first a-amination using cinchona alkaloids was shown in 1,3-dicarbonyl substrate systems. In 2004, Pihko and coworkers showed enantioselective a-amination of cyclic fi-ketoesters 130, with dibenzyl azodicarboxylate (131) in the presence of... 

Preparation of Aryl Hydrazines. All methods mentioned above for the hydrazination of alkyl carbanions may also be applied to aryl carbanions. Addition of phenyllithium to a cyclic azo compound followed by in situ arylation to give a tetrasubstituted hydrazine was mentioned earlier (Eq. 19). An alternate hydrazination method, not involving aryl anions, is the reaction of electron-rich arenes with azodicarboxylic esters and aroylazocarboxylic esters under the influence of various catalysts.230,377-384... 

Diels-Alder adducts of various azodicarboxylates have been used extensively in synthesis of cyclic azoalkanes44 and pyridazine derivatives.1-29 Since previous reviews have adequately dealt with this material, it will not be reiterated here. 

Aza-l-thia-1,3-butadiene, 232-233 1-Azirine, 57-59 Azirine, 232, 257 Azo compound, 154-163 Azoalkene, 267-270 cyclic, 156 Azobenzene, 156 Azodicarboxylate, 202, 269-271 acyclic, 154-156 cyclic, 156-160 ester, 154... 

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