Ketimines ketones

In the review period, most syntheses of phosphonic acids and their derivatives involved simple organophosphorus reagents, like diallq l and trialkyl phosphites that were widely used in reactions with aHqmes and alkenes including bromoalkenes to obtain alkenyl and allqmylphospo-nates as well as with imines, ketimines, ketones, aldehydes and nitriles to afford imino- and aminophosphonates, and hydroxyphosphonates. Two or more component reactions were also utilised in these syntheses. 

Other modifications of the polyamines include limited addition of alkylene oxide to yield the corresponding hydroxyalkyl derivatives (225) and cyanoethylation of DETA or TETA, usuaHy by reaction with acrylonitrile [107-13-1/, to give derivatives providing longer pot Hfe and better wetting of glass (226). Also included are ketimines, made by the reaction of EDA with acetone for example. These derivatives can also be hydrogenated, as in the case of the equimolar adducts of DETA and methyl isobutyl ketone [108-10-1] or methyl isoamyl ketone [110-12-3] (221 or used as is to provide moisture cure performance. Mannich bases prepared from a phenol, formaldehyde and a polyamine are also used, such as the hardener prepared from cresol, DETA, and formaldehyde (228). Other modifications of polyamines for use as epoxy hardeners include reaction with aldehydes (229), epoxidized fatty nitriles (230), aromatic monoisocyanates (231), or propylene sulfide [1072-43-1] (232). 

Also due to the high barrier of inversion, optically active oxaziridines are stable and were prepared repeatedly. To avoid additional centres of asymmetry in the molecule, symmetrical ketones were used as starting materials and converted to oxaziridines by optically active peroxyacids via their ketimines (69CC1086, 69JCS(C)2648). In optically active oxaziridines, made from benzophenone, cyclohexanone and adamantanone, the order of magnitude of the inversion barriers was determined by racemization experiments and was found to be identical with former results of NMR study. Inversion barriers of 128-132 kJ moF were found in the A-isopropyl compounds of the ketones mentioned inversion barriers of the A-t-butyl compounds lie markedly lower (104-110 kJ moF ). Thus, the A-t-butyloxaziridine derived from adamantanone loses half of its chirality within 2.3 days at 20 C (73JCS(P2)1575). 

The ketimine is an acetone-blocked diamine. The synthesis and applications of ketimines will be discussed later. The curing concept for the adhesive is shown in Fig. 7. Phenol-blocked prepolymers would normally unblock at approximately 150°C. However, an aliphatic diamine, generated by the hydrolysis of the ketimine to an aliphatic diamine and ketone as a result of exposure to the moisture in the air, is sufficient to cure the windshield adhesive at room temperature. 

Several blocked diamines or amino-alcohols are commercially available. The aldimine is an aldehyde-blocked diamine. The ketimine is a ketone-blocked diamine. The oxazolidine is a five-membered ring containing oxygen and nitrogen. The oxazolidine ring shown below is an aldehyde-blocked amino alcohol. The basic synthetic concepts of an aldimine, a ketimine, and an oxazolidine are shown below ... 

Once the adhesive system is applied, water reacts preferentially with the more reactive ketimine, instead of with the slower reacting isocyanate. In the presence of water, the ketimine unblocks to reform the ketone and diamine. Once formed, the diamine will react quickly with the isocyanate to form a polyurea. 

We have previously discussed that keto-aldehydes react with anilines first at the aldehyde carbon to form the aldimine. Subsequent condensation with another aniline formed a bis-imine or enamino-imine. The aniline of the ketimine normally cyclizes on the aldimine (24 —> 26). Conversely, cyclization of the aldimine could be forced with minimal aniline migration to the ketimine using PPA (30 —> 31). The use of unsymmetrical ketones has not been thoroughly explored a few examples are cited below. One-pot enamine formation and cyclization occurred when aniline 48 was reacted with dione 49 in the presence of catalytic p-TsOH and heat. Imine formation occurred at the less-hindered ketone, and cyclization with attack on the reactive carbonyl was preferred. ... 

The insertion of alkynes into a chromium-carbon double bond is not restricted to Fischer alkenylcarbene complexes. Numerous transformations of this kind have been performed with simple alkylcarbene complexes, from which unstable a,/J-unsaturated carbene complexes were formed in situ, and in turn underwent further reactions in several different ways. For example, reaction of the 1-me-thoxyethylidene complex 6a with the conjugated enyne-ketimines and -ketones 131 afforded pyrrole [92] and furan 134 derivatives [93], respectively. The alkyne-inserted intermediate 132 apparently undergoes 671-electrocyclization and reductive elimination to afford enol ether 133, which yields the cycloaddition product 134 via a subsequent hydrolysis (Scheme 28). This transformation also demonstrates that Fischer carbene complexes are highly selective in their reactivity toward alkynes in the presence of other multiple bonds (Table 6). 

Scheme 6.17 Synthesis of poly(ether ketone) via poly(ether phenyl ketimine).

Hedrick et al. reported imide aryl ether ketone segmented block copolymers.228 The block copolymers were prepared via a two-step process. Both a bisphenol-A-based amorphous block and a semicrystalline block were prepared from a soluble and amorphous ketimine precursor. The blocks of poly(arylene ether ether ketone) oligomers with Mn range of 6000-12,000 g/mol were coreacted with 4,4,-oxydianiline (ODA) and pyromellitic dianhydride (PMDA) diethyl ester diacyl chloride in NMP in the presence of A - me thy 1 morphi 1 i nc. Clear films with high moduli by solution casting and followed by curing were obtained. Multiphase morphologies were observed in both cases. 

The Schiff reaction between chitosan and aldehydes or ketones yields the corresponding aldimines and ketimines, which are converted to N-alkyl derivatives upon hydrogenation with borohydride. Chitosan acetate salt can be converted into chitin upon heating [130]. The following are important examples of modified chitosans that currently have niche markets or prominent places in advanced research. 

C. Reactions not involving P=0 or P=S Groups.—Enamine phosphine oxides (45) have been prepared by the addition of amines to 1-alkynyl-phosphine oxides, and the reactions of their anions with various electrophiles have been reported. - With ketones a Wittig-type reaction leads to the formation of a/3-unsaturated ketones, in 53—70% yield, while with epoxides cyclopropyl ketimines are formed. A Diels-Alder reaction of l-phenyl-A -phospholen-l-oxide (46) with 1,4-diacetoxybutadiene has been used in the preparation of l-phenyl-benzo[/>]phosphole (47), as... 

Figure 1.5 Structure resemblance between ketone aniline 36 and ketimine 5.

Among them, (1 R,2S)-l-phenyl-2-(l-pyrrolidinyl)propan-l-ol (46) was selected as a chiral modifier for further optimization. It is interesting to point out that N-methyl ephedrine was not a suitable chiral modifier for ketimine 5 (only 10% ee as shown in Table 1.2), but in the case of ketone 41, N-methyl ephedrine provided a respectable 53% ee, as shown in Table 1.5. 

Scheme 6.148 Ketimines from ketones and primary amines.

A mechanism has been proposed for this, and related transformations, involving a chelation assisted C-H bond functionalization. Following hydride addition to the solvent, acetone, and a transmetallation reaction, reductive elimination yields the ketimine. Hydrolysis of the latter affords the ketone (Equation (131)).114 114a... 

Similarly, ketimines (benzylimines of aromatic ketones) undergo the rhodium-catalyzed ortho-alkenylation with alkynes to give or/ o-alkenylated aromatic ketones after hydrolysis.61 This method is applied to an efficient one-pot synthesis of isoquinoline derivatives by using aromatic ketones, benzylamine, and alkynes under Rh catalysis (Equation (55)). 

A ketimine can also be alkylated by the same process.140 In situ generation of a ketimine from the aromatic ketone 114 and benzylamine provides an efficient catalytic process with Wilkinson catalyst (Scheme 35). The alkylated aromatic ketone 115 is obtained in good yield. Better reactivity and selectivity are obtained with ketimine... 

Addition of RMgBr to nitriles. Grignard reagents react with nitriles slowly if at all, but even r-butylmagnesium chloride will add to nitriles in refluxing THF when catalyzed by a copper(I) salt. The adduct can be converted to a ketimine by anhydrous protonation, to a primary amine by reduction (Li/NH,), or to a ketone by hydrolysis. The actual reagent may be a cuprate such as R3Cu(MgX)2. 

Ketimines, enamines from, in ketones alkylation, 54, 48 Ketone, aralkyl, selective a-bromination of, 53, 111 Ketone, a,a -dibromodineopen-tyl-, preparation of, 54,... 

The ketone synthesis of Houhen and Hoesch, which is based on the principle of the Gattermann reaction, proceeds very smoothly and gives very favourable results, especially in the case of polyhydric phenols. In this synthesis nitriles are used. Here it is the iminochlorides R—C=NH which are converted into ketimines and then into ketones, a... 

While this example of the Robinson annulation is clearly not enantioselec-tive, the same antibody converts the mero-ketone [120] into the Wieland-Miescher (WM) decalenedione product kcM = 0.086 min-1 and Km = 2.34 mM at 25°C, parameters that give an impressive ER of 3.6 x 106. Good evidence suggests that the mechanism of the reaction involves the formation of a ketimine with the e-amino group of a buried lysine residue in the antibody, as shown in Fig. 39. Most significantly, the reaction delivers the ( )-(+)-WM product in 96% ee (by polarimetry) and in 95% ee by nmr and hplc analysis for a 100 mg scale reaction. A recent report tells that this antibody is to be made commercially available at a cost of 100 for 10 mg. The realization of that objective would mark the start of a new era of application of abzymes to organic stereoselective synthesis. 

The indirect anodic oxidation of ketones 42 in ammonia - containing methanol using iodide as a mediator afforded 2,5-dihydro-IH-imidazols 44 via oxidation of the intermediate ketimine 43 to AT-iodo imine followed by elimination of HI to afford the nitrenium ion, which subsequently reacts with ketimine 43 to give the product 44 [73] (Scheme 23). 

The electrolysis of asymmetric ketones 43 led to the formation of isomers and stereoisomers. Kinetic measurements for the formation of ketimine 43 in saturated ammoniacal methanol indicated that at least 12 h of the reaction time were required to reach the equilibrium in which approximately 40% of 42 was converted into the ketimine 43. However, the electrolysis was completed within 2.5 h and the products 44 were isolated in 50-76% yields. It seems that the sluggish equilibrium gives a significant concentration of ketimine 43 which is oxidized by the 1 generated at the anode, and the equilibrium is shifted towards formation of the product 44. 2,5-Dihydro-IH-imidazols of type 44, which were unsubstituted on nitrogen, are rare compounds. They can be hydrolyzed with hydrochloric acid to afford the corresponding a-amino ketones as versatile synthetic intermediates for a wide variety of heterocyclic compounds, that are otherwise difficult to prepare. 

Prior to imide formation, the imide-aryl ether ketimine copolymers were converted to the imide-aryl ether ketone analogue by hydrolysis of the ketimine moiety with para-toluene sulfonic acid hydrate (PTS) according to a literature procedure [51,52,57-59]. The copolymers were dissolved in NMP and heated to 50 °C and subjected to excess PTS for 8 h. The reaction mixtures were isolated in excess water and then rinsed with methanol and dried in a vacuum oven to afford the amic ester-aryl ether ether ketone copolymer, 2e (Scheme 8.)... 

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