Imines compounds

There are some special cases where tetrahedral intermediates are unusually stable there are three phenomena which lead to this stability enhancement. The first is an unusually reactive carbonyl (or imine) compound which is very prone to addition. An example of such a compound is trichoroacetaldehyde or chloral, for which the covalent hydrate can be isolated. A simple way to recognize such compounds is to think of the carbonyl group as a (very) stabilized carbocation, bearing an substituent. 

Hagiwara et al.107 reported the chiral Pd(II) complex-catalyzed asymmetric addition of enol silyl ethers to imines, based on the belief that Pd(II) enolate was involved in the reaction. They found that with compound 171a as the catalyst, very low enantioselectivity was obtained in the asymmetric reactions between silyl enol ether and imine compounds (Scheme 3-58). However, in the... 

This chapter has introduced the aldol and related allylation reactions of carbonyl compounds, the allylation of imine compounds, and Mannich-type reactions. Double asymmetric synthesis creates two chiral centers in one step and is regarded as one of the most efficient synthetic strategies in organic synthesis. The aldol and related reactions discussed in this chapter are very important reactions in organic synthesis because the reaction products constitute the backbone of many important antibiotics, anticancer drugs, and other bioactive molecules. Indeed, study of the aldol reaction is still actively pursued in order to improve reaction conditions, enhance stereoselectivity, and widen the scope of applicability of this type of reaction. 

Hydrosilylation of imine compounds was also an efficient method to prepare amines. The hydrosilylation product TV-silylamines can readily be desilylated upon methanol or water treatment, yielding the corresponding amines. The amines can be converted to their corresponding amides by subsequent acyl anhydride treatment. The first attempt to hydrogenate prochiral imines with Rh(I) chiral phosphine catalysts was made by Kagan102 and others. These catalysts exhibited low catalytic activity, and only moderate ee was obtained. 

Denmark and Kallemeyn have described the mild palladium-catalyzed insertion of 1,2-diethoxy-1,1,2,2,-tetra-methyldisilane EtOMe2SiSiMe2OEt into aryl bromides RBr affording aryldimethylsilyl ethers RMe2SiOEt and Me2SiBrOEt in high yields.750 Williams and Tanaka et al. have reported on the palladium- and platinium-catalyzed reaction of carbonyl and imine compounds with disilanes.7... 

It has been reported by R.Scheiner that phenylazide forms triazoline compounds by 1,3-cyclic addition to unsaturated olefines such as n-butylethylene and norbornen(9 ). These triazolines are decomposed photochemically or thermally to give imine compounds and aziridine as is shown in scheme 1. These facts suggest that phenylazide may react with 3-methyl-1-butene to give triazoline in a similar reaction to that with norbomen. 

Until 2006, a severe limitation in the field of chiral Brpnsted acid catalysis was the restriction to reactive substrates. The acidity of BINOL-derived chiral phosphoric acids is appropriate to activate various imine compounds through protonation and a broad range of efficient and highly enantioselective, phosphoric acid-catalyzed transformations involving imines have been developed. However, the activation of simple carbonyl compounds by means of Brpnsted acid catalysis proved to be rather challenging since the acid ity of the known BINOL-derived phosphoric acids is mostly insufficient. Carbonyl compounds and other less reactive substrates often require a stronger Brpnsted acid catalyst. 

The phenol-imine (pale yellow) structure retains a fully conjugated aromatic ring on the left side of the molecule, while the keto-enamine (red) compound has a quinoidal structure. Due to the benefits of aromaticity, the more stable phenol-imine compound requires a higher energy of excitation and appears pale yellow. 

Similarly, the enamine salt 15 is obtained by lithiation of 14 (equation 5). In both cases the lower steric hindrance leads to higher stability of the enaminic system33 where the double bond is formed on the less substituted carbon. The Af-metalated enamines 11 and 15 are enolate analogs and their contribution to the respective tautomer mixture of the lithium salts of azomethine derivatives will be discussed below. Normant and coworkers34 also reported complete regioselectivity in alkylations of ketimines that are derived from methyl ketones. The base for this lithiation is an active dialkylamide—the product of reaction of metallic lithium with dialkylamine in benzene/HMPA. Under these conditions ( hyperbasic media ), the imine compound of methyl ketones 14 loses a proton from the methyl group and the lithium salt 15 reacts with various electrophiles or is oxidized with iodine to yield, after hydrolysis, 16 and 17, respectively (equation 5). 

Organolithium species may form coloured and EPR-active intermediates not only with conventional acceptors such as carbonyl or imine compounds [14-16] but also with unsaturated inorganic ions such as ambidentate thiocyanate-SCN the reaction between n-BuLi and NH4SCN in the presence of strongly ion-stabilizing hexamethylphosphoric triamide 0 = P(NMe2)3 (HMPA) eventually produced LiNCS 2 HMPA via some unusually colored intermediates and thiocyanate-based radical species [62]. 

Benzophenone with tertiary amines has been used to polymerize bis 2-[2-(methacryloyloxy)ethoxy]ethyl phthtilate and triethylene glycol dimethacrylate in bulk, while mixtures of ZnO and l,8-diamino-3,6-diazaoctane have been used to emulsion-polymerize styrene. An internal keto-imine compound,... 

The nitromethyl-imine macrocycle compounds are reduced by Zn/HCl to aminomethyl-imine compounds (92), which are reduced by NaBH4 to 5-aminomethyl-cyclam compounds (93). 

Case 2 is much simpler and concerns nucleophilic additions to a prostereogenic carbonyl or imine compound 45-1. In this case the newly created stereogenic center at C-1 is influenced by R and Z with respect to matched and mismatched combinations. In principle the influence of or Z may be more dom-... 

Imine Compound of the type R2C=NR formed by the reaction of an aldehyde or a ketone with a primary amine (R NH2). Imines are sometimes called Schijfs bases. 

The imine compounds are then reacted with metal salts of dialkyl phosphonates with formula 4 to yield secondary aminophosphonates 5. Reduction of the secondary aminophosphonates furnished the corresponding aminophosphonates having structure 6. 

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