Amines enamine

Typical nucleophiles known to react with coordinated alkenes are water, alcohols, carboxylic acids, ammonia, amines, enamines, and active methylene compounds 11.12]. The intramolecular version is particularly useful for syntheses of various heterocyclic compounds[l 3,14]. CO and aromatics also react with alkenes. The oxidation reactions of alkenes can be classified further based on these attacking species. Under certain conditions, especially in the presence of bases, the rr-alkene complex 4 is converted into the 7r-allylic complex 5. Various stoichiometric reactions of alkenes via 7r-allylic complex 5 are treated in Section 4. 

Hydroamination of alkynes offers a straightforward preparation of a variety of amines, enamines, and imines.79 Numerous reports have appeared in the literature on this process. However, almost all these reactions have been carried out in organic solvents, which usually require the protection of functional groups or harsh conditions. Recently, Marinelli et al. have reported an Au(III)-catalyzed hydroamination of alkynes in... 

The most characteristic reaction of butadiene catalyzed by palladium catalysts is the dimerization with incorporation of various nucleophiles [Eq. (11)]. The main product of this telomerization reaction is the 8-substituted 1,6-octadiene, 17. Also, 3-substituted 1,7-octadiene, 18, is formed as a minor product. So far, the following nucleophiles are known to react with butadiene to form corresponding telomers water, carboxylic acids, primary and secondary alcohols, phenols, ammonia, primary and secondary amines, enamines, active methylene compounds activated by two electron-attracting groups, and nitroalkanes. Some of these nucleophiles are known to react oxidatively with simple olefins in the presence of Pd2+ salts. Carbon monoxide and hydrosilanes also take part in the telomerization. The telomerization reactions are surveyed based on the classification by the nucleophiles. 

Keywords Aldehydes and ketones Alpha-fnnctionalization Amines Enamine catalysis Organocatalysis... 

Secondary amine reacts with aldehyde and ketone to produce enamine. An enamine is an a,P-unsaturated tertiary amine. Enamine formation is a reversihle reaction, and the mechanism is exactly the same as the mechanism for imine formation, except the last step of the reaction. 

Azide addition to enamines may be employed to shift amine-enamine equilibria (Scheme 52).209... 

In analogy to the classification of organic amines, enamines are called primary (20), secondary (21) or tertiary (22) depending on the extent of substitution on nitrogen. 

Prepared from the primary amines, enamines bearing one proton on the nitrogen (1) would tautomerize to imine isomers (T) (equation 1). 

Referring to a mechanistic classification of organocatalysts (Seayad and List 2005), currently the two most prominent classes are Brpnsted acid catalysts and Lewis base catalysts. Within the latter class chiral secondary amines (enamine, iminium, dienamine activation for a short review please refer to List 2006) play an important role and can be considered as—by now—already widely extended mimetics of type I aldolases, whereas acylation catalysts, for example, refer to hydrolases or peptidases (Spivey and McDaid 2007). Thiamine-dependent enzymes, a versatile class of C-C bond forming and destructing biocatalysts (Pohl et al. 2002) with their common catalytically active coenzyme thiamine (vitamin Bi), are understood to be the biomimetic roots ofcar-bene catalysis, a further class of nucleophilic, Lewis base catalysis with increasing importance in the last 5 years. 

Oxidation. Bis(p-methoxyphenyl)telluroxide (1) is a mild and selective oxidant for conversion of xanthates, thiocarbamates, thioamides, and nonenolizable thiones into the corresponding oxo derivatives, and also of thiols into disulfides. Typically these reactions afford products in 70-100% yield. 1,2- and 1,4-Hydroquinones are oxidized by 1 to o- and p-quinones, respectively. Phenylhydroxylamine is oxidized to nitrosobenzene (90% yield). Phenols, amines, enamines, alcohols, oximes, dithiolanes, isonitriles, and 2,4-dinitrophenylhydrazones are unreactive. 

Oxidation. Triphenylbismuth carbonate suspended in CH2CI2 is a heterogeneous oxidant for a variety of functional groups. Allylic alcohols are efficiently oxidized to the corresponding unsaturated aldehydes or ketones, even in the presence of a thiol, which is itself oxidized by this reagent to a disulfide, cis- and Irani-1,2-Glycols are cleaved to dialdehydes hydrazones are oxidized to diazocompounds oximes are cleaved to ketones and 1,2-dialkylhydrazines are oxidized to azo compounds. Phenylhydrazones, semicarbazones, tosylhydrazones, aromatic and aliphatic amines, enamines, and enol ethers are inert to 1. 

A 2° amine reacts with an aldehyde or ketone to give an enamine. Enamines have a nitrogen atom bonded to a double bond zSkene + amine = enamine). 

Ethylene transfer to dibasic nucleophiles. The reagent reacts with primary amines, enamines, and active methylene compounds ... 

Catalytic hydroamination of imsaturated carbon-carbon bonds has a strong potential for the access to a large variety of amines, enamines or imines [90]. The first addition of a N-H bond to alkynes catalyzed by a ruthenium catalyst was described in 1995 by Watanabe et al. [91], and involved a ruthenium-catalyzed addition of the N-H bond of N-formyl anilines to terminal alkyne (Scheme 8.29). 

Nucleophilic substitution and addition reactions of olefins are possible with Pd2 salts. A typical example is the formation of acetaldehyde by the reaction of ethylene with water (Wacker reaction). As nucleophiles, water, alcohols, phenols, carboxylic acids, amines, enamines, carbanions derived from active methylene compounds, and carbon monoxide react with olefins with stoichiometric consumption of Pd2 salts. 

Palladium-phosphine complexes such as Pd [PPh3 ]4 or, most conveniently, Pd(OAc)2 and PPh3 are used. Usually, these telomers are obtained in high yields. Nucleophiles such as water, carboxylic acids, alcohols, phenols, ammonia, amines, enamines, nitroalkanes, and active methylene and methyne compounds participate in telomerization. Also, carbon monoxide and hydrosilanes are involved in the reaction to give telomers. These easily available telomers are trifunctional and extremely useful starting materials for simple synthesis of certain types of natural products. 

Aromatization also occurs easily if alcohol, thiol, or amine can be eliminated from a trans-arrangement of substituents. The cycloaddition step is especially fast if ketene aminals, enamines, enol ethers, enol esters, or trimethylsilyloxyalkenes are used as 27t-compounds. The reaction enthalpy A/f for the eycloaddition of 1,3-eyelopentadiene or 1-hexene to dimethyl tetrazinedicarboxylate is in the range of 60-70 kcal mol <93ZORi7i9>. 

Dinitrophenylhydrazones, R2C=N-NH-C6Hj(N02)2 (e) Addition of secondary amines enamines (Section 19.9)... 

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