From Imides

Polymerization by G—G Goupling. An aromatic carbon—carbon coupling reaction has been employed for the synthesis of rigid rod-like polyimides from imide-containing dibromo compounds and aromatic diboronic acids ia the presence of palladium catalyst, Pd[P(CgH )2]4 (79,80). 

It was anticipated that two of the three stereochemical relationships required for intermediate 12 could be created through reaction of the boron enolate derived from imide 21 with a-(benzyloxy)ace-taldehyde 24. After conversion of the syn aldol adduct into enone 23, a substrate-stereocontrolled 1,2-reduction of the C-5 ketone car-... 

A key step in the synthesis of the spiroketal subunit is the convergent union of intermediates 8 and 9 through an Evans asymmetric aldol reaction (see Scheme 2). Coupling of aldehyde 9 with the boron enolate derived from imide 8 through an asymmetric aldol condensation is followed by transamination with an excess of aluminum amide reagent to afford intermediate 38 in an overall yield of 85 % (see Scheme 7). During the course of the asymmetric aldol condensation... 

The synthesis of the polyol glycoside subunit 7 commences with an asymmetric aldol condensation between the boron enolate derived from imide 21 and a-(benzyloxy)acetaldehyde (24) to give syn adduct 39 in 87 % yield and in greater than 99 % diastereomeric purity (see Scheme 8a). Treatment of the Weinreb amide,20 derived in one step through transamination of 39, with 2-lithiopropene furnishes enone 23 in an overall yield of 92 %. To accomplish the formation of the syn 1,3-diol, enone 23 is reduced in a chemo- and... 

A-Acyliminium ions, which are even more reactive toward allylic and alkenyl-silanes, are usually obtained from imides by partial reduction (see Section 2.2.2). The partially reduced A-acylcarbinolamines can then generate acyliminium ions. Such reactions have been employed in intramolecular situations with both allylic and vinyl silanes. 

Samarium(II) iodide also allows the reductive coupling of sulfur-substituted aromatic lactams such as 7-166 with carbonyl compounds to afford a-hydroxyalkylated lactams 7-167 with a high anti-selectivity [74]. The substituted lactams can easily be prepared from imides 7-165. The reaction is initiated by a reductive desulfuration with samarium(ll) iodide to give a radical, which can be intercepted by the added aldehyde to give the desired products 7-167. Ketones can be used as the carbonyl moiety instead of aldehydes, with good - albeit slightly lower - yields. 

Chiral diazaphosphoramides 278 were obtained from imide-amide rearrangement of the corresponding oxazaphosphorimidate precursors 277 derived from optically active (R)-/V-l-bcnzylaminopropan-2-ol (276) (Scheme 66) [104],... 

TABLE 2-5. Diastereoselective Alkylation Reaction of the Lithium Enolates Derived from Imides 22 and 23... 

Imidates, or even nitrogen compounds produced from imidates by the addition of nucleophiles, may be obtained from oximes by a Beckmann rearrangement-addition process. 

OXAZOLINES FROM NITRILES AND AMINO ALCOHOLS, 385-386 OXAZOLINES FROM IMIDATES AND AMINO ALCOHOLS, 388-389 CONVERSION OF ALLYLIC ALCOHOLS TO P-AMINO ALCOHOLS VIA OXAZO-... 

Since formamide is a weak nucleophile, the use of imidazole or 4-dimethylaminopyridine (DMAP) is necessary for acyl transfer to formamide via an activated amide (imidazolide) or acylpyridinium ion. As Scheme 22 illustrates, the reaction starts with the oxidative addition of aryl bromide 152 to Pd(0) species, followed by CO insertion to form acyl-Pd complex 154. Imidazole receives the aroyl group to form imidazolide 155 and liberates HPdBr species. Then, imidazolide 155 reacts with formamide to form imide 156. Finally, decarbonylation of imide 156 gives amide 157. In fact, the formations of imidazolide intermediate 155 and imide 156 as well as the subsequent slow transformation of imide 156 to amide 157 by releasing CO were observed. This mechanism can accommodate the CO pressure variations observed during the first few hours of aminocarbonylation. When the reaction temperature (120 °C) was reached, a fast drop of pressure occurred. This corresponds to the formation of the intermediary imide 156. Then, the increase of pressure after 3 h of reaction was observed. This phenomenon corresponds to the release of CO from imide 156 to form amide 157. ... 

In the region from 150°C to 250 °C both solvent evolution and maximum evolution of water from imidization takes place. 

N-AMINO COMPOUNDS FROM IMIDE SODIUM SALTS AND DPHa... 

Table 15 Syntheses of Symmetrical 1,3,5-Triazines from Imidates <6uoc2778>...

The direct formation of the equilibrium mixture of amide rotamers from the fragmentation of tetrahedral intermediates for imidate salts 138A and 138B is thus rationalized. The same explanation is also valid for the formation of the equilibrium mixture of the amide rotamers 139A and 139B from imidate salts 137A and 137B. 

In a study on the aminolysis of O-acetylethanolamine (185, R =H) and 0-acetylserine (185, R =COOH), it was observed (41) that the kinetics of acetyl-transfer reaction of these two aminoesters indicate that the breakdown of 186 yields mainly the amidoalcohol 187 only 1.5-3% of aminoester 185 was detected. The breakdown of 186 was compared with that of 188 obtained from imidate 94 (cf. p. 130) which gave only the aminoester 95 by C-N bond cleavage. Contrary to the conclusion reached by these authors (41), the difference in behavior between 186 and 188 can be readily understood. Imidate salt 94 reacts with hydroxide ion to give conformer J89 (R=CH3) which can only give the aminoester 95 with stereoelectronic control the amino-... 

Amidines 21 derived from imidates 20 and thiophenes 1 were cyclized into... 

Figure 3.19 Cylindrical capsules from imides and ureas at the bridges of cavitands.

Figure 7.2 illustrates the phosphorus pentoxide-mediated dehydration of a primary amide to a nitrile, using the transformation of nicotine amide (A) into nicotine nitrile (B) as an example. The reaction of phosphorus pentoxide at the carboxyl oxygen furnishes the partially ring-opened iminium ion E (simplified as F) via the polycyclic iminium ion C. E is deprotonated to give the mixed anhydride G from imidic acid and phosphoric acid. Imidic acids are characterized by the functional group R-C(=NH)-OH. This anhydride is transformed into the nitrile B by an El elimination via the intermediate nitrilium salt D. Nitrilium salts are iV-pro-tonated or V-alkylated nitriles. 

Stereoselective rearrangement reactions can involve sugar-linked functionalities. An example of this type is the Overman rearrangement of allylic trichloracetimidates formed from a D-glucofuranose derivative 20 [36]. This methods affords (L)-a-ami-no acids 25 from (Z)-allylic imidate 23 and (R)-a-amino acids 25 from ( )-imidates 23 with a diastereoselectivity of about 16 1. The oxidative cleavage of compound 24 with Ru04 yields the a-amino acid 25, (Scheme 15). 

R. T. Coutts and A. M. K. El-hawari, Heterocycles 2, 669-743 (1974). Synthesis of heterocycles, from imides of sulfur dioxides ... 

Kerneur, G., Lerestif, J.M., Bazureau, J.P., and Hamelin, J. 1997. Convenient preparation of 4-alkylidene-l//-imidazol-5(4//)-one derivatives from imidate and aldehydes by a solvent-free cycloaddition under microwaves. Synthesis, 287-89. 

Polyimides for microelectronics use are of two basic types. The most commonly used commercial materials (for example, from Dupont and Hitachi) are condensation polyimides, formed from imidization of a spin-cast film of soluble polyamic acid precursor to create an intractable solid film. Fully imidized thermoplastic polyimides are also available for use as adhesives (for example, the LARC-TPI material), and when thermally or photo-crosslink able, also as passivants and interlevel insulators, and as matrix resins for fiber-reinforced-composites, such as in circuit boards. Flexible circuits are made from Kapton polyimide film laminated with copper. The diversity of materials is very large readers seeking additional information are referred to the cited review articles [1-3,6] and to the proceedings of the two International Conferences on Polyimides [4,5]. 

A select set of useful [4 + 2] cycloaddition reactions of simple 2-aza-1,3-butadienes have been detailed (Table 11), " and in most instances the 2-azadienes employed are substituted with strong electron-donating substituents responsible for enhancing its Diels-Alder reactivity toward electron-deficient dienophiles. The ease with which the l,3-bis(t-butyldimethylsilyloxy)-2-aza-1,3-butadienes may be prepared from imides, and the demonstrated facility with which they participate in HOMOdiene-controlled [4 + 2] cycloaddition reactions, may prove exceptionally useful their use constitutes the most general approach to implementing the 477 participation of 2-aza-1,3-butadienes (Scheme 12). With the recent introduction of a convenient preparation of 3-trimethylsilyloxy-2-aza-1,3-butadienes, their comparable synthetic utility may be anticipated. ... 

Acetylamidrazones (20) can be made from imidate hydrochlorides and acetohydrazide in dry ethanol in the presence of triethylamine (Scheme 4.3.10). When treated with phenacyl bromide in boiling acetonitrile they are largely converted into 1-acetamidoimidazoles (21), although some acetylamidrazone hydrobromide also precipitates. Yields of (21) are around 46-64% with alkyl or aryl 2-substituents [511. 

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