Imides acyclic

Imide-terminated telechelics are also synthesized by metathesis depolymerization, and it is found that phthalimide-substituted olefins allow for productive depolymerization when only one methylene spacer separates the nitrogen atom and the olefin (Fig. 8.21). This combination of steric hindrance around the nitrogen lone pair and decreased electron donation from resonance prevents the negative neighboring group effect. However, secondary acyclic amines are unable to produce telechelics through metathesis depolymerization because of unfavorable catalyst-amine interactions. 

Imides can be prepared by the attack of amides or their salts on acyl halides, anhydrides, and carboxylic acids or esters. The best synthetic method for the preparation of acyclic imides is the reaction between an amide and an anhydride at 100°C catalyzed by H2S04. When acyl chlorides are treated with amides in a2 l molar ratio at low temperatures in the presence of pyridine, the products are N,N-diacylamides, (RCO)3N. ... 

Arguably the most challenging aspect for the preparation of 1 was construction of the unsymmetrically substituted sec-sec chiral bis(trifluoromethyl)benzylic ether functionality with careful control of the relative and absolute stereochemistry [21], The original chemistry route to ether intermediate 18 involved an unselective etherification of chiral alcohol 10 with racemic imidate 17 and separation of a nearly 1 1 mixture of diastereomers, as shown in Scheme 7.3. Carbon-oxygen single bond forming reactions leading directly to chiral acyclic sec-sec ethers are particularly rare since known reactions are typically nonstereospecific. While notable exceptions have surfaced [22], each method provides ethers with particular substitution patterns which are not broadly applicable. 

Sulfur and nitrogen form a variety of binary anions with acyclic, cyclic and cage structures.69,70 The Se-N anions are only known in metal complexes. S-N anions play an important role in the formation of cyclic sulfur imides and as constituents of solutions of sulfur in liquid ammonia. 

Asymmetric Diels-Alder reactions. Unlike methyl crotonate, which is a weak dienophile, chiral (E)-crotonyl oxazolidinones when activated by a dialkylaluminum chloride (1 equiv.) are highly reactive and diastereoselective dienophiles. For this purpose, the unsaturated imides formed from oxazolidinones (Xp) derived from (S)-phenylalanol show consistently higher diastereoselectivity than those derived from (S)-valinol or (IS, 2R)-norephedrine. The effect of the phenyl group is attributed in part at least to an electronic interaction of the aromatic ring. The reactions of the unsaturated imide 1 shown in equation (I) are typical of reactions of unsaturated N-acyloxazolidinones with cyclic and acyclic dienes. All the Diels-Alder reactions show almost complete endo-selectivity and high diastereoselectivity. Oxazolidinones are useful chiral auxiliaries for intramolecular Diels-Alder... 

Crossover experiments have been used to establish that the novel N to C acyl migration reaction of acyclic imides (69), to give o -amino ketones (70), proceeds by intramolecular reaction of the base-generated carbanion. ... 

The formation of tluorinated Q -hydroxy-jS-imino esters (180) by treatment of fluorinated imino ethers (179) with lithium 2,2,6,6-tetramethylpiperidide has been reported. A possible explanation for this interesting intramolecular rearrangement is proposed in Scheme 64. Acyclic imides derived from primary benzylic amines and amino acid esters have been found to undergo a novel nitrogen to carbon acyl migration via a base-generated carbanion to yield the corresponding a-amino... 

The scope of Michael additions with catalysts containing cyclohexane-diamine scaffolds was broadened by Li and co-workers [95]. When screening for a catalyst for the addition of phenylthiol to a,p-nnsatnrated imides, the anthors fonnd that thiourea catalyst 170 provided optimal enantioselectivities when compared to Cinchon alkaloids derivatives (Scheme 41). Electrophile scope inclnded both cyclic and acyclic substrates. Li attributed the enantioselectivity to activation of the diketone electrophiles via hydrogen-bonding to the thiourea, with simultaneous deprotonation of the thiol by the tertiary amine moiety of the diamine (170a and 170b). Based on the observed selectivity, the anthors hypothesized that the snbstrate-catalyst... 

The tri- and tetracyclic derivatives 321-323 were prepared in the reactions of 312-315 and lactim ethers instead of acyclic imidates [79JCS(P1)1765 82JCS(P1)2801 83JCS(P2)237 90PHA109 94MI1]. 

Now where does the discrepancy lie An acyclic paradigm was used for the oxi-mate/imidate interconversion. Had we used the plausibly aromatic paradigm of isoxa-zole/oxazole, the isomerization enthalpy would have been 95 kJ moR where the requisite enthalpies of formation are from References 76 and 1, respectively. This difference is meaningfully distinct from that of the acyclic paradigm but still does not particularly ameliorate the difference. Is it possible that the N—O bond in aryl and alkyl oxime ethers are profoundly different Could it be that we have neglected any antiaromaticity in the 8 n... 

Scheme 6.70 Mechanistic proposal for the 12-catalyzed asymmetric Michael addition of malononitrile to (J-aryl and alkyl substituted N-acyl pyrrolidinones (cyclic imide) (A) and to a,P-unsaturated N-aryl substituted 2-methoxybenzamides such as N-cinnamoyl-2-methoxybenzamide (acyclic imide) (B).

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