Diimide precursors

Diimide can act as both a hydrogen acceptor and donor, undergoing disproportionation as a side-reaction which produces a considerable amount of nitrogen gas. From a practical point of view the occurrence of this disproportionation reaction requires the use of an excess of the diimide precursor. 

Potassium loaded on a porous silicon nitride has been reported as a superbase catalyst. With appropriate pre-treatment, the catalyst was found to be highly active for 2,3-dimethylbut-l-ene isomerisation yielding 2,3-dimethylbut-2-ene in close to 100% selectivity. In order for high activity to be demonstrated, 30 wt% potassium amide was loaded by impregnation. A trace of Fc203 was also added on impregnation. A silicon nitride synthesised via a silicon diimide precursor which was pre-treated at 1000°C was found to be best and the catalyst was activated by heating in vacuo. The possibility that this resulted in active potassium nitride species via ... 

Catenane 177, devoid of triple bonds, has been prepared by macrocyclization of a 1,4,5,8-naphthalenetetracar-boxylate diimide precursor bearing ethylene glycol chains and pyromellitic diimide, under standard Mitsunobu alkylation conditions, in the presence of crown ether 170 <20000L449>. 

Diimide precursors Chloroacetylhydrazide hydrochloride. Hydrazine. Hydroxylamine-O-sulfonic acid. Potassium azodicarboxylate. o-Diketone adduct Triethyl phosphite. 

Potassium azodicarboxylate and triethylamine hydrochloride are placed in flask C, and this section of the apparatus is connected to the vacuum line and evacuated. The breakseal is then broken with the magnet, and the evacuated apparatus is removed from the vacuum line and tilted to pour the phenyldiazene solution onto the diimide precursors. Phenylhydrazine formation is detected by measuring the ultraviolet spectrum of the solution via the quartz cell. Over the course of a few hours, the spectrum changes from that of phenyldiazene to that of phenylhydrazine. 

Reductions with azodicarboxylic acid, a diimide precursor s. 77,83 preferential reduction of ar. 0x0 compounds s. E. E. van Tamelen, M. Davis, and M. F. Deem, Ghem. Comm. 1965, 71... 

Reductions with azodicarboxylic acid, a diimide precursor... 

An organocatalytic reduction of nonconjugated double bonds, which overcomes both mentioned obstacles, makes use of diimide, generated in situ from hydrazine. Commonly, diimide is generated from a large excess of hydrazine hydrate with periodate or oxygen and carboxylic acids. Alternatively, anhydrous hydrazine in the presence of Cu(II) can be used or diimide precursors as o-nitrophenylsulfonyl hydrazide. To lower the amount of hydrazine, Imada et al. used a flavin-based catalyst to... 

Di Antonio, M. Doria, F. Mella, M. Merli, D. Profumo, A. Freccero, M. Novel naphthalene diimides as activatable precursors of bisalkylating agents, by reduction and base catalysis. J. Org. Chem. 2007, 72, 8354—8360. 

Since the corresponding endoperoxide precursors are all too unstable for isolation, the diimide reduction constitutes an important chemical structure confirmation of these elusive intermediates that are obtained in the singlet oxygenation of the respective 1,3-dienes. However, the aza-derivative 14 and the keto-derivative 15 could not be prepared,17> because the respective endoperoxides of the pyrroles 18) and cyclopentadienones suffered complex transformations even at —50 °C, so that the trapping by the diimide reagent was ineffective. 

The reduction of polymers can be carried out by using a diimide, generated in situ. The precursor for diimide can be p-toluenesulfonyl hydrazide (TSH), the reaction temperature is between 110-160 °C and the solvents are high boiling aromatic compounds. Possible side-reactions are cis-trans isomerization of 1,4-dienes, attachment of hydrazide fragments to the polymer, degradation and cyclization of the polymer. 

Amino-1,2,3-triazoles with a substituent at the 4-position have been prepared (i) from azides and active methylene nitriles (ii) from azides and ynamines (iii) from diazomethane and carbo-diimides (iv) from azides and 1,1-diaminoethenes and (v) from the rearrangement of 3-hydrazono-1,2,4-oxadiazoles. Among these, the first method, a regiospecific process, is the most versatile and convenient although it is suitable only for 5-NH2-substituted triazoles. Other methods are used to prepare 5-NHR , 5-NR R - and 5-NHCOR-substituted triazoles. Intramolecular cyclization of suitable precursors also gives 5-aminotriazoles. For example, a-imino-a-piperidyl phenylhydrazones (838), in the presence of copper acetate, give 5-piperidyl-triazoles (839) (Equation (85)) <94H(38)739>. 

Of the array of aromatic diimides available, PMIs (1), NDIs (2), and PDIs (3) (Figure 11.1) have been the most widely used, owing to the commercial availability of the starting dianhydride precursors. Although the PDIs are the most attractive in terms of their optical properties, they suffer tremendously from solubility problems-that is, aggregation. In particular, substituted NDIs form stable radical anion and dianion species [1-7], so from this aspect NDIs have become more attractive as supramolecular components. In recent years, NDIs have been shown to be a powerful tool in organic supramolecular chemistry to separate charges from photoexcited donor molecules. In this respect, NDIs are utilized as the electron acceptors [2-5]. 

Baylis-Hillman adducts such as 55 and 56 derived from 2-nitrobenzaldehydes were shown to function as useful precursors to functionalized (1H)-quinol-2-ones and quinolines. Treatment of 55 and 56 with iron and acetic acid at 110 °C afforded 57 and 58, respectively <02T3693>. A variety of other cyclization reactions utilized in the preparation of the quinoline scaffold were also reported. An iridium-catalyzed oxidative cyclization of 3-(2-aminophenyl)propanols afforded 1,2,3,4-tetrahydroquinolines <02OL2691>. The intramolecular cyclization of aryl radicals to prepare pyrrolo[3,2-c]quinolines was studied <02T1453>. Additionally, photocyclization reactions of /rans-o-aminocinnamoyl derivatives were reported to provide 2-quinolones and quinolines <02JHC61>. Enolizable quinone and mono- and diimide intermediates were shown to provide quinolines via a thermal 6jt-electrocyclization <02OL4265>. Quinoline derivatives were also prepared from nitrogen-tethered 2-methoxyphenols. The corresponding 2-methoxyphenols were subjected to a iodine(III)-mediated acetoxylation which was followed by an intramolecular Michael addition to afford the quinoline OAc O... 

The initial scission of cyclobutane ring of available pagodane derivative 37 is achieved as a result of homolytic bromination. The tribromide 38, thus formed, underwent facile bromine elimination-fragmentation (and hydrogenolysis of the C-Br bond at the a-methoxycarbonyl center) under the action of metals to form diene 39. Diimide reduction of 39 affected only one double bond and gave product 40, which served as a common precursor for both 35 and 36. The... 

Dibnide. This hydrazine decomposes at temperatures between 35 and 65° to give diimide. It can be used for hydrogenation of olefins in good yield. Benzenesulfonyl-hydrazine and p-toluenesulfonylhydrazine have been used as precursors of diimide but much higher temperatures are required for generation of diimide from these precursors. 

Two strategies have been developed for the preparation of esters of diazoacetic acid. If the alcohol is inexpensive, it is first converted (diketene) into the corresponding acetoacetate (120 equation 49). Diazo transfer with subsequent deacylation then yields the diazoacetate (121). If the alcohol is particularly valuable or sensitive, it may alternatively be esterified with a more direct precursor to diazoacetate. One reagent that has been used for this purpose is glyoxalic acid 2,4,6-triisopropylbenzenesulfonylhydrazone (TIPPS) (123 equation 50). Esterification of the alcohol (122) with (123), using dicyclohexylcarbo-diimide followed by addition of 4-dimethylaminopyridine, gives the diazoacetate (124). ... 

According to a preliminary report, diimide can be generated at 0° by the action of sodium hydroxide on chloroacetylhydrazide hydrochloride (which see). Another precursor is hydroxylamine-O-sulfonic acid (which see). Azobenzene has been reduced quantitatively to hydrazobenzene and tdlyl alcohol to propanol (70%). ClCHjCONHNHi HCl + 2 NaOH ----------> CH2=C=0 + HjO + HN=NH + 2 NaCff... 

Terminal acetylenes are selectively hydrogenated to alkenes in the presence of the iron(II) precursors [P(CH2CH2PPh3) FeH(X2) BPh4] (X = N or H) under mild conditions in THF. Cw-Addition of hydrogen to 1-iodoalkynes is brought about by reaction with diimide, N2H2. ... 

About ten years ago I was involved in the chemistry of diimide, and therein started an interest in molecular nitrogen as well. Just about ten years ago. Professor Burris and I carried out an experiment at the University of Wisconsin designed to reveal the role of intermediates in the enzymic conversion of nitrogen into ammonia. The experiment involved the feeding of a N-labelled precursor of diimide (specifically azodi-carboxylic acid) to the nitrogen-fixing enzyme system. That experiment, needless to say, was negative. 

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