Carbodiimides reaction

Cycloaddition Reactions. Carbodiimides also react as dipolarophiles in [2+3] cycloaddition reactions. For example, generation of diphenylnitryl imine 292 in the presence of diphenylcarbodiimide affords a spiro compound 293 as the result of the reaction of the initially formed [2+3] cycloadduct with a second equivalent of the nitrile imine. ... 

Also, the presence of strong bases, even in trace amounts, can promote the formation of isocyanurates or carbodiimides. In the event of gross contamination, the exothermic reaction can sharply increase the temperature of the material. Normally, the trimerization reaction occurs first and furnishes heat for the carbodiimide reaction. The carbodiimide reaction Hberates carbon dioxide and forms a hard soHd. The Hberation of carbon dioxide in a sealed vessel could result in overpressurization and mpture. 

Other six-membered rings with two heteroatoms are also obtained from reaction of diketene with imidates, cyanamides, carbodiimides, isocyanates, oxa2olines, or other multiftmctional compounds. 

Other Reactions. 2-Dioxolaniniines, 2-oxathiolaniniines, and 2-oxa2o1idinimines result from the reaction of propylene oxide with isocyanates, isothiocyanates, and carbodiimides, respectively (103,104). 

In a manner analogous to classic nitrile iinines, the additions of trifluoro-methylacetonitrile phenylimine occur regiospecifically with activated terminal alkenes but less selectively with alkynes [39], The nitnle imine reacts with both dimethyl fumarate and dimethyl maleate m moderate yields to give exclusively the trans product, presumably via epimenzation of the labile H at position 4 [40] (equation 42) The nitrile imine exhibits exo selectivities in its reactions with norbornene and norbornadiene, which are similar to those seen for the nitrile oxide [37], and even greater reactivity with enolates than that of the nitnle oxide [38, 41], Reactions of trifluoroacetomtrile phenyl imine with isocyanates, isothiocyanates, and carbodiimides are also reported [42]... 

Finally, attachment of a rather complex side chain to the para position of the benzene ring on the sulfonamide leads to the very potent, long-acting oral antidiabetic agent, glyburide (215). Preparation of this compound starts with the chlorosul-fonation of the acetamide of 3-phenethylamine (209). The resulting sulfonyl chloride (210) is then converted to the sulfonamide (211) and deacylated (212). Reaction with the salicylic acid derivative, 213, in the presence of carbodiimide affords the amide, 214. Condensation of that with cyclohexylisocyanate affords glyburide (215). ... 

Mechanism of amide formation by reaction of a carboxylic acid and an amine with dicyclohexyl-carbodiimide (DCC). 

The reaction of /V-aminotriazines 847 with diaryl carbodiimides led (88H161) directly to the new triazolotriazines 848, which display mesoionic character (Scheme 172). 

Cycloadditions of isocyanates and their derivatives with vinyiaziridines were first reported by Alper and coworkers. From their previous studies of cydoadditions to vinylepoxides or alkylaziridines, they investigated cydoadditions to vinyiaziridines and found that such reactions with isocyanates, carbodiimides, or isothiocyanates in the presence of catalytic amounts of Pd(OAc)2 (2 mol%) and PPh3 (10 mol%) at room temperature afforded five-membered ring products 249 in 34—97% yields (Scheme 2.61) [91]. When an aziridine 247 possessing an alkyl substituent at the... 

Activating agents, such as trifluoroacetic anhydride 1,1 -carbonyldiimidazolc carbodiimides sulfonyl, tosyl, and picryl chlorides and a range of phosphorus derivatives can promote direct solution reactions between dicarboxylic acids and diols or diphenols in mild conditions. The activating agents are consumed during the reaction and, therefore, do not act as catalysts. These so-called direct polycondensation or activation polycondensation reactions proceed via the in situ transformation of one of the reactants, generally the carboxylic acid, into a more... 

Carbodiimide functionality can be produced by reacting isocyanates at elevated temperature with proper catalysis (Scheme 4.15). Although carbodiimides undergo a variety of reactions,23 most commonly as dehydrating agents, in the presence of excess isocyanate they will form uretone imines. This not only increases the average functionality of the isocyanate product but also lowers its freezing point. For example, a liquefied (or modified) version of 4,4,-MDI can... 

Poly (ethylene oxide) macromonomers72 761 are made in a similar way, as the alkoxide end group is reactive enough towards benzylic halides. With methacryloyl chloride, side reactions are involved. It is better to first protonate the PEO, and then to have it react with methacryloyl chloride in the presence of some triethyl amine. One can also react co-hydroxy polyethylene oxide) with methacryloyl imidazole, or with methacrylic acid in the presence of dicyclohexyl carbodiimide (DCCf)77). 

Lee et al. reported a novel and simple method for delivery of adriamycin using self-aggregates of deoxycholic acid modified chitosan. Deoxycholic acid was covalently conjugated to chitosan via a carbodiimide-mediated reaction generating self-aggregated chitosan nanoparticles. Adriamycin was... 

Wang recently reported [30] that thermolysis of carbodiimides 15 (Scheme 1.5) in aromatic solvents is an efficient route to indoloquinolines 18 used as precursors for synthesizing naturally occurring alkaloids [31], The cyclization is thought to occur through a two-step biradical Diels-Alder reaction that gives 17, which then tautomerizes to 18. 

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