Irradiation With Secondary and Primary Amines

Direct Irradiation With Secondary and Primary Amines 

Whereas most reactions of singlet arenes and aryl olefins with secondary amines result in N-H addition, there are exceptions to this generalization. Cookson et al. reported that irradiation of 1-phenylcyclohexene in isopropylamine yielded a mixture of N-H and a-C-H adducts. Gilbert and co-workers ° found that the reaction of benzene with dimethylamine yields N-H adducts, whereas pyridine reacts with diethylamine to yield the substitution product 11, which presumably is formed by aromatization of the a-C-H adduct. Irradiation of stilbene and indole in mixed crystals yields both N-H and C-H adducts, product ratios being dependent upon the reactant ratio. Investigation of the reactions of 9-cyanophenanthrene with primary and secondary 

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JE. Direct Irradiation With Secondary and Primary Amines... 

Irradiation with Tertiary Amines Irradiation with Secondary and Primary Amines ET Sensitized Irradiation with Ammonia and Primary Amines... 

The reaction between epoxides and ammonia (or ammonium hydroxide) is a general and useful method for the preparation of (3-hydroxyamines. With epoxide derived from terminal alkenes, the reaction with ammonia gives largely the primary amine, but secondary and tertiary amine products are possible from the appropriate epoxide. The reaction of 121 with ammonium hydroxide with microwave irradiation, for example, gave 122. Ethanolamines, which are useful solvents... 

Direct irradiation of [60]fuUerene 47 in the presence of trimethylamine is reported to yield the adducts 47a and 47b as primary and secondary products (Scheme 29). Only small amounts of these adducts are isolated from complex product mixtures. Formation of 47a is proposed to occur via an electron transfer, proton transfer, radical coupling mechanism similar to that for addition of stilbene and trialky-lamines. Formation of 47b is found to require oxidation of 47a by singlet fuUerene. Direct irradiation of 47 with dimethylamine in the presence of air is reported to result in the formation of the tetra(amino)fullerene epoxide 47c (Scheme 29). Isolated yields as high as 98% are reported for the reaction of N-methylpiperazine. More hindered secondary amines such as EtjNH and primary amines fail to undergo this extraordinary reaction. 

This is the most common method for the preparation of enamines and usually takes place when an aldehyde or ketone containing an a hydrogen is treated with a secondary amine. The water is usually removed azeotropically or with a drying agent, but molecular sieves can also be used. Stable primary enamines have also been prepared.Enamino-ketones have been prepared from diketones and secondary amines using microwave irradiation on silica gel. ° Secondary amine perchlorates react with aldehydes and ketones to give iminium salts (2, p. 1178). Tertiary amines can only give salts (12). 

Pr)4, " borohydride-exchange resin,and formic acid. When the last is used, the process is called the Wallach reaction. Conjugated aldehydes are converted to alkenyl-amines with the amine/silica gel followed by reduction with zinc borohydride.In the particular case where primary or secondary amines are reductively methylated with formaldehyde and formic acid, the method is called the Esch-weiler-Clarke procedure. It is possible to use ammonium (or amine) salts of formic acid, " or formamides, as a substitute for the Wallach conditions. This method is called the Leuckart reaction,and in this case the products obtained are often the N-formyl derivatives of the amines instead of the free amines. Primary and secondary amines can be iV-ethylated (e.g., ArNHR ArNREt) by treatment with NaBH4 in acetic acid. Aldehydes react with aniline in the presence of Mont-morillonite KIO clay and microwaves to give the amine. Formaldehyde with formic acid converts secondary amines to the N-methyl derivative with microwave irradiation. 

The methylation of secondary amines works better than for primary amines because there is no competition between the formation of mono- or dimethylated products. The best results for the microwave-enhanced conditions were obtained when the molar ratios of substrate/formaldehyde/formic acid were 1 1 1, so that the amount of radioactive waste produced is minimal. The reaction can be carried out in neat form if the substrate is reasonably miscible with formic acid/aldehyde or in DM SO solution if not. Again the reaction is rapid - it is complete within 2 min at 120 W microwave irradiation compared to longer than 4 h under reflux. The reaction mechanism and source of label is ascertained by alternatively labeling the formaldehyde and formic acid with deuterium. The results indicate that formaldehyde contri-... 

The reaction between alkyl hahdes and ammonia or primary amines is not usually a feasible method for the preparation of primary or secondary amines, since they are stronger bases than ammonia and preferentially attack the substrate. However, the reaction is very useful for the preparation of tertiary amines and quaternary ammonium salts. If ammonia is the nucleophile, the three or four alkyl groups on the nitrogen of the product must be identical. If a primary, secondary, or tertiary amine is used, then different alkyl groups can be placed on the same nitrogen atom. The conversion of tertiary amines to quaternary salts is called the Menshutkin reaction It is sometimes possible to use this method for the preparation of a primary amine by the use of a large excess of ammonia or a secondary amine by the use of a large excess of primary amine. The use of ammonia in methanol with microwave irradiation has also been effective. Microwave irradiation has also been used in reactions of aniline with allyl iodides. A base other than the amine... 

Irradiation of the diazepine N-oxide 8 gives a mixture of the 1,2-dihydroquinoxaline (10) and the oxadiazocine 11 through an intermediate oxaziridine (9). The dihydroquinoxaline undergoes acid hydrolysis to the quinoxalinone 12. It was subsequently shown that quinoxalinones of type 12 undergo ready reaction with ammonia or primary or secondary amines, in the presence of titanium tetrachloride, to give 3-amino- or... 

In a parallel study [162] it was shown that formamide and primary and secondary amines react with esters in the presence of potassium fert-butoxide under microwave irradiation. Substituted amides are formed in yields (generally more than 70%) much higher than under the action of conventional heating (Eq. (78), Table 4.27) ... 

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