Imines reagents

Quenching polystyryllithium and polybutadienyllithiums with A-benzylidenemethyl-amine (PhCH=NMe) in benzene solution leads to amine-functionalized polymers (equation 103), that can be characterized by SEC, TLC, acid-base titration and H and C NMR spectroscopies. The end groups are monomeric. Gradual addition of Et20 reduces the yields. This is attributed to increased reactivity of the alkyllithium residues in the polymer, bringing about a concurrent metallation reaction of the imine reagent (e.g. equation 101) . 

Fluoral hydrate and hemiacetals are industrial products. They are stable liquids that are easy to handle, and they react as fluoral itself in many reactions. Thus, in the presence of Lewis acids, they react in Friedel-Crafts reactions. They also react very well with organometallics (indium and zinc derivatives) and with silyl enol ethers.Proline-catalyzed direct asymmetric aldol reaction of fluoral ethyl hemiac-etal with ketones produced jS-hydroxy-jS-trifluoromethylated ketones with good to excellent diastereo- (up to 96% de) and enantioselectivities. With imine reagents, the reaction proceeds without Lewis acid activation. The use of chiral imines affords the corresponding 8-hydroxy ketones with a 60-80% de (Figure 2.49). ° ... 

In this case, the trimethylsilyl group linked to the nitrogen atom allows the imine reagent to assume the required cationic nature for giving the Mannich reaction. The imine group, however, also can be activated by protonation.- ... 

A fluorous imine reagent (3), also commercially available, was introduced by Herr as an ammonia equivalent in the Buchwald-Hartwig amination of aryl bromides, iodides, and triflates (Reaction Scheme 9)3 In this case, the problem of introducing a primary amine was solved by the use of (3) as a synthon for ammonia. 

The imine reagent 106 was synthesized in four steps starting from the chloroacetate 109 that was submitted to the Arbuzov reaction. After deprotection of the hydroxy group and Jones oxidation, the resulting aldehyde 110 was condensed with cyclohexylamine. 

While the isomerization of activated (i.e., bearing electron-deficient groups) alkynes into 1,3-dienes is well documented, the challenging isomerization of non-activated alkynes into 1,3-enynes has been less investigated. In 2006, Hayashi reported the Rh-catalyzed isomerization of unactivated alkynes to conjugated dienes promoted by the azomethine imine reagent 20 (Scheme 14) [30]. Thus,... 

The cyclic 2,4-dienoate 184, formed by the Pd-catalyzed cyclization of the 1,6-enyne 183, reacted with 154 to form the azulene derivative 185[118], The 3-methylenepyrrolidine 188 is formed by the reaction of the Zn reagent 186 with the chiral imine 187 with high diastereomeric excess. The structure of the allylic ethers is important for obtaining high diastereoselectivity[l 19],... 

Aromatization of indolines is important in completing synthetic sequences in which the directive effects of the indoline ring have been used to achieve selective carbocyclic substitution[l]. Several methods for aromatization have been developed and some of these are illustrated in Table 15.2. A range of reagents is represented. One type of procedure represents use of oxidants which are known to convert amines to imines. Aromatization then provides the indole. Such reagents must not subsequently oxidize the indole. Mereuric acetate (Entry 1) is known to oxidize other types of amines and presumably reacts by an oxidative deprotonation ot- to the complexed nitrogen. 

Write an equation showing how you could prepare ethyl phenyl ketone from propanenitrile and a Grignard reagent What is the structure of the imine intermediate ... 

The reactions of ketenes or ketene equivalents with imines, discussed above, all involve the imine acting as nucleophile. Azetidin-2-ones can also be produced by nucleophilic attack of enolate anions derived from the acetic acid derivative on the electrophilic carbon of the imine followed by cyclization. The reaction of Reformatsky reagents, for example... 

Lithium aluminum hydride (LiAlH4) is the most powerful of the hydride reagents. It reduces acid chlorides, esters, lactones, acids, anhydrides, aldehydes, ketones and epoxides to alcohols amides, nitriles, imines and oximes to amines primary and secondary alkyl halides and toluenesulfonates to... 

Carbon-nitrogen multiple bonds in fluorinated imines and nitriles react with halogen fluoride reagents Imines provide 7V-chloroamine.s on reaction with chlo rme fluoride [62, 121, 122, 123] (equations 23 and 24) or with cesium fluoride and chlorine [124] and A -bromoammes on reaction with cesium fluoride and bromine (equation 24)... 

Modification of the Erlenmeyer reaction has been developed using imines of the carbonyl compounds, obtained with aniline," benzylamine or n-butylamine. Ivanova has also shown that an A-methylketimine is an effective reagent in the Erlenmeyer azlactone synthesis. Quantitative yield of 19 is generated by treatment of 3 equivalents of 2-phenyl-5(4ff)-oxazolone (2) (freshly prepared in benzene) with 1 equivalent of iV-methyl-diphenylmethanimine (18) in benzene. Products resulting from aminolysis (20), alkali-catalyzed hydrolysis (21), and alcoholysis (22) were also described. 

Toward the end of the 19 century both Pomeranz and Fritsch independently reported the preparation of isoquinolines by the reaction of aminoacetaldehyde dimethyl acetal 2 (R = Me) with aromatic aldehydes 1 followed by cyclisation in acidic media. " Unfortunately yields were often poor and not always reproducible. This has prompted the search for various improvements and modifications on the original theme, including the use of reagents other than strong mineral acid which tends to destroy the intermediate imine. ... 

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