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Azaheterocycles Based on A, ß-Unsaturated Carbonyls

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Returns are shipped at the customer's risk. We cannot take responsibility for items which are lost or damaged in transit. For purchases where a shipping charge was paid, there will be no refund of the original shipping charge. Chebanov, Sergey M. Publisher Description. About Us. N-chloroderivatives of aziridinyl ketones can be pene [64], are known. The action of N2O4 on azirinochal- Reactions characterizing aziridinyl ketones as polyfunc- cones in the presence of triethylamine leads to chalcones tional compounds are also described in the literature.

An [71]. Such inhibition of the cyclization Methylthiocyanate reacts with BF3 complexes of 3- stage results in the formation of acyl hydrazone 56 as a by- aroylaziridines yielding 4-arylaroylmethylthio product as well as the formation of pyrazole 55 from the imidazoazolines. During this reaction the three-membered intermediate aminopyrazoline by a rapid trans-elimination.

N-Unsubstituted pyrazoles are synthesized by action of Among the numerous bibliographies related to this question hydrazine on compounds Examples zoles. This reaction will be considered in more detail in the of such reactions are the thermal isomerization of aroyl az- section 1. In particular, 2,2-dimethyl 4- iodide [83] Scheme 1. The reaction is reversible: azirenoimidazoles un- cyclohexylbenzoyl 2-nitrophenyl aziridine 68 into dergo reverse transformation forming trans-aziridinyl ke- quinoline 69 [14]: tones in acetic acid.

The transformation of works []. The method consists water was added to the reaction mixture [86]. But the authors [95] note that both when using benzalde- hyde as a carbonyl and the intermediate aziridinyl ketone is 1. Synthesis of Bi- and Tricyclic Aziridine Derivatives less soluble in alcohol then the starting dibromide in par- One of the initial findings about bicyclic aziridines is ticular, for 1-aryl-2,3-dibromo 4-nitrophenyl propan ones , it is advisable to carry out the synthesis in two steps published in the work [88]; the authors carried out the syn- thesis of 3,5a-dihydro-1H-azireno[1,2-c]imidazoles by react- with separating the intermediate aziridinyl ketone.

For example, it is proposed [88] that hydes 82 and ammonium acetate under microwave irradia- the first stage of the reaction is the addition of a carbonyl tion [97] Scheme 1. The authors Scheme 1. However, target azirenoimi- ammonia molecule, releasing the aziridine iminogroup which dazoles 83 containing different substituents in positions 2 reacts with the carbonyl compound and subsequently cy- and 8 can not be obtained by this method. It is noted, in particular, that carrying out the reaction work [89]: endo- and exo-isomers 85A and 85B, respec- in methanol for 1 hour with the use of N,N-dimethyl- tively were obtained in the reaction of transphenyl benzylamine as a catalyst increased the yield of It should benzoylaziridine 18 with ammonia and benzaldehyde 84 and be noted that nucleophilic addition of the second amino separated by fractional crystallization Scheme 1.

The authors have shown the possi- ]. Scheme 1. Investigations of the mechanism of the reactions of dia- The work [] reports about the synthesis of aziridines mines with 2,3-dibromopropanones have not been re- containing polyfluoroalkyl substituents on the aziridine cy- ported in early works.

An assumption about the mechanism cle.

The results also investigation of a reaction utilizing 4-nitro-1,2-phenylene- provide information about the reaction mechanism. As well diamine. The authors [] assumed ing to the compound Dihydroazirenoquinox- tem unstable and promoting additional transformations. It was shown that even under mild conditions, atoms which are basic centers. The most interesting reactions i. HCl, aprotonic solvent, isomerization into the 2- are the processes involving the carbon-carbon single bond of benzylquinoxaline derivatives took place Scheme 1.

The authors could not isolate the salts as they had made for The possibility of bicyclic aziridine hydrochloride salt azirenoimidazoles and azirenopyrazines [88, ]. On the formation was first mentioned in the work [88]. The hydro- basis of the experiments carried out, as well as previous data chlorides of some azirenoimidazoles were obtained by pass- [], a conclusion was made about the initial protonation on ing dry hydrogen chloride through ether solutions. However, the azomethine nitrogen atom. The electron-withdrawing the protonation direction has not been established in this influence of the protonated azomethine group on the az- work.

After the attack, the heteroaromatic system work [] in detail.

Aminoazoles as Key Reagents in Multicomponent Heterocyclizations

The authors note that protonation not is formed which is the most energetically favorable process. A 1- 4-nitrophenyl phenyl-3,5a-dihydro-1H-azireno[1,2- reaction is also described where the C-N bond of the imida- c]imidazole and 1- 4-nitrophenylphenyl-1,3,4,6a- zole cycle is broken [88].

It is shown that a rearrangement tetrahydroazireno[1,2-a]pyrazine hydrochlorides were ob- leading to pyrimidine takes place under the action of tained according to the procedure [88]. Compound can be easily reduced by so- can be formed: two by conrotatory and two by disrotatory dium borohydride to the corresponding N-hydroxy derivative ring-opening Scheme 1.

C bond of the sterically strained three-membered cycle, The reaction of dipolar cycloaddition of S-shaped ylides namely thermo- and photoinduced cycloaddition reactions. The heteroatomic diethyl fumarate analogue can also act as a dipolarophile with its reaction leading to the Ar H imidazotriazole Chemical properties of dihydroazirenoquinoxalines are Ar N conrot.

H N studied in the work [] and it is shown that these com- pounds react in numerous cycloadditions via cleavage of the H H Ar H C-C bond of the aziridine cycle as well. Cycloaddition reactions of dihydroazirenoquinoxalines cis trans proceed under milder conditions than those for dihydroazire- noimidazoles.

As it was already mentioned, the action of Scheme 1. The trans-substituted aziridines are as Scheme 1.

14.01 alpha,beta-Unsaturated Carbonyl Compounds

Thermal decomposition or action of nitro- follows Scheme 1. As well as for the case of the trans-aziridine must take place in a conrotatory manner dihydroazirenoimidazoles, reactions with a series of symmet- leading to cis-ylide and photochemical opening via a disrota- rical dipolarophiles such as compounds , , , tory one giving trans-azomethine ylide. Reactions with asymmetrical dipolarophiles, scribed in the literature are concerned with cycloaddition in particular, with benzaldehyde 84, proceed chemoselec- reactions.

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For example, it was shown in one of the first tively and lead in this case to dihydrooxazoloquinoxalines works [93] that refluxing azirenoimidazole 72 with different The same result was obtained by other authors [] compounds containing multiple C-C bonds in p-xylene led to who studied the chemical properties of 5,6-dimethyl-1,1a- the corresponding adducts via cleavage of the C-C bond of dihydroazireno[1,2-a]quinoxalines.

In particular, the reaction of 72 with N- The structure of the products enabled authors [] to phenylmaleimide leads to compound and interaction propose that the intermediate of the reactions described is an with diethyl acetylene dicarboxylate , diethyl fumarate azomethine ylide Scheme 1. If a 4-nitrophenyl substituent is attached to the aziridine observed which rapidly disappeared upon heating. A single cycle of the dyhydroazirenoquinoxaline molecule, charge cycloadduct was found and isolated from the reaction delocalization involving the nitro-group resulting in a qui- mixture.

The authors [] consider that its formation pro- noid-type structure is possible Scheme 1.

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  • Azaheterocycles Based on a,ß-Unsaturated Carbonyls?

These data were obtained in the opening. Cycloadduct was also obtained in a thermal work []. But the formation of the that the intermediate of the reaction is a planar azomethine identical reaction products from endo- and exo-isomers of ylide.

Three-Membered Azaheterocycles Based on &#; , &#;-Unsaturated Ketones | Bentham Science

Therefore, the both isomers as an intermediate. Otherwise if the initial attack on the aziridine Similar to the preceding results, the corresponding enedi- cycle turned away from imidazole ring plane took place then imine was isolated Scheme 1. The same situation is observed with another pair of course of the reaction due to irradiation. To ascertain the cycloadducts B and D which are formed in equal structure of the colored intermediate the authors [90] at- quantities as well.

When the dipolarophile The preservation of the relative configuration of the dipo- was added to the reaction mixture, the coloration immedi- larophile substituents in all cycloadducts is evidence for the ately disappeared and the corresponding cycloadduct concerted cycloaddition mechanism.

Irradiation of 72 with tetracyanoethylene An investigation of the aziridinyl anile transformations in gave the adduct in high yield. Based upon these data, a solutions without dipolarophiles addition is carried out in the structure of azomethine ylide formed by aziridine carbon- work [89] where behaviour of the isomeric azirenoimida- carbon bond cleavage is assigned to the colored intermediate.

Another reaction pathway is observed in methanol []. The second presupposes initial formation of chemical process [, ]. The fact that addition of the ylide subsequently becoming the imidazoline R1 substituents led to the coloration deepening. Inductive effects R have much less influence than conjugation effects. Moving the nitro-group to the meta-position of the aromatic ring which excludes it from the Scheme 1.

The deepest coloration is inherent in the compounds containing that ylide and enediimine are in equilibrium and the solvent the 5-nitrothienyl substituent instead of the 4-nitrophenyl. Much less influence on photochromic properties is ex- When azirenoimidazoles were first synthesized [88] their erted by the substituent R1 where the relationship between photochromic properties were discovered: all the crystalline substituent character and the position of the absorption band 6- 4-nitrophenyl substituted aziridines, colorless or yel- maximum of the colored species is difficult to discover.

Photo- withdrawing properties of the substituent R1 led to reducing chromism was also observed for azirenoimidazoles hydro- the time for decoloration in the dark.

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Their crystals became red upon irradiation. Photo- Photochromic properties also depend on the bridge group chromic properties were also found for azirenoimidazoles M. Introducing a nitro group as an R substituent results pyrazines and dihydroazirenoquinoxalines as well as for az- in eliminating the role of the bridge group.

This property is most pronounced for com- It is noted [] that the rate of dark decoloration reduces pounds containing the 4-nitrophenyl substituent on the az- drastically with increasing temperature. In particular, for iridine cycle. In contrast to bases becoming blue in the [] possessed photochromic properties. The most pro- light, the photo-induced form of the salts is red colored. The nounced influence on photochromic properties is caused by authors [] explain this by a different electron density dis- the substituent R found in the ring directly attached to the tribution in the photo-induced form.