Carbodiimides preparation

TABLE 2. Physical Properties of Step 2 Macrocyclic Carbodiimides Prepared by Ring Closure of Step 1 Product Using l,3-Dimethyl-3-phospholene Oxide... 

Weil988 Weinshenker, N.M., Shen, C.M. and Wong, J.Y, Polymeric Carbodiimide. Preparation, Organic Synthesis, Coll. Vol. VI, (1988) 951-954. 

The selenoureas needed for condensation can usually be prepared by addition of hydrogen selenide to a solution of the corresponding cyanamides or carbodiimides. They can be less dangerously and quite... 

Bisa2iridine compounds and A/-(2-chloroethyl)carbodiimides have also been prepared using isocyanide dichlorides and ethyleneimine (178,179). The iodide-cataly2ed rearrangement of the formerly mentioned compounds provides a method for preparing the tetrahydroimida2oimida2ole system ... 

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). ... 

The amount of resin used contains about 0.012 mole of active carbodiimide. Methods for preparing this reagent, determining its carbodiimide content, and regenerating spent resin are described in the preceeding procedure (p. 95). 

Carbodiimides have been prepared by desulfurization of thioureas by metal oxides, by sodium hypochlorite,4 or by ethyl chloroformate in the presence of a tertiary amine by halogena-tion of ureas or thioureas followed by dehydrohalogenation of the N,N -disubstituted carbamic chloride 8 and by dehydration of disubstituted ureas using -toluenesulfonyl chloride and pyridine.7 The method described above is a modification of that of Campbell and Verbanc. ... 

One of the simplest ways to prepare a chitin gel is to treat chitosan acetate salt solution with carbodiimide to restore acetamido groups. Thermally not reversible gels are obtained by AT-acylation of chitosans N-acetyl-, N-propionyl- and N-butyryl-chitosan gels are prepared using 10% aqueous acefic, propionic and bufyric acid as solvents for treatment with appropriate acyl anhydride. Both N- and 0-acylation are found, but the gelation also occurs by selective AT-acylation in the presence of organic solvents. 

The synthesis, structures, and reactivity of neutral and cationic mono- and bis(guanidinato)zirconium(rV) complexes have been studied in detail. Either salt-metathesis using preformed lithium guanidinates or carbodiimide insertion of zirconium amides can be employed. Typical examples for these two main synthetic routes are illustrated in Schemes 73 and 74. Various cr-alkyl complexes and cationic species derived from these precursors have been prepared and structurally characterized. 

Diazametallacycles of the type Cp2Zr[Bu NC( = NR )NR ] have been prepared according to Scheme 92 from terminal zirconium imides and carbodiimides. A second series of analogous compounds was synthesized starting... 

A (pentamethylcyclopentadienyl)iridium chelating guanidinate complex has been conveniently prepared by treatment of [Cp IrCl2]2 with N,N, N"-th-p-tolylguanidine and base in THF at room temperature followed by recrystallization of the green product from toluene and pentane (Scheme 154). Insertion reactions of the product with heterocumulenes (diaryl carbodiimides, aryl isocyanates) have been investigated. It was found that the complex serves as highly active catalyst for the metathesis of diaryl carbodiimides with each other and for the more difficult metathesis of diaryl carbodiimides with aryl isocyanates (cf. Section V.C). ... 

A similar approach, i.e., carbodiimide insertion into M-N bonds was used to prepare unusual zirconacarboranes containing guanidinate ligands. In an alternative approach, these compounds were also synthesized by the route outlined in Scheme... 

Oxalamidinate anions represent the most simple type of bis(amidinate) ligands in which two amidinate units are directly connected via a central C-C bond. Oxalamidinate complexes of d-transition metals have recently received increasing attention for their efficient catalytic activity in olefin polymerization reactions. Almost all the oxalamidinate ligands have been synthesized by deprotonation of the corresponding oxalic amidines [pathway (a) in Scheme 190]. More recently, it was found that carbodiimides, RN = C=NR, can be reductively coupled with metallic lithium into the oxalamidinate dianions [(RN)2C-C(NR)2] [route (c)J which are clearly useful for the preparation of dinuclear oxalamidinate complexes. The lithium complex obtained this way from N,N -di(p-tolyl)carbodiimide was crystallized from pyridine/pentane and... 

Reaction of Ph2PLi with Pr N = C = NPr in THF proceeds via insertion of the carbodiimide into the Li-P bond, affording the lithium phosphaguanidinate salt Li[Ph2PC(NPr )2] in 72% yield. The preparation and reactivity of this new ligand are summarized in Scheme 217. An X-ray crystal structure analysis of the product obtained after removal of the solvent from the reaction mixture revealed the presence of a mono-solvated, centrosymmetric dimer in the solid state (Figure... 

Cyanamide can be stannylated under various conditions to give bis(stannyl)carbodiimides (224-227), and bis(stannyl)sulfurdiimides have been prepared from the reaction between S4N4 and trimethyldi-methylaminotin (228). 

The reaction between acyl halides and diazomethane is of wide scope and is the best way to prepare diazo ketones. Diazomethane must be present in excess or the HX produced will react with the diazo ketone (10-74). This reaction is the first step of the Amdt-Eistert synthesis (18-8). Diazo ketones can also be prepared directly from a carboxylic acid and diazomethane or diazoethane in the presence of dicyclohexyl-carbodiimide. ... 

A variation of this process uses carbodiimides, which can be prepared by the dehydration of N,N -disubstituted ureas with various dehydrating agents, among which are TsCl in pyridine, POCI3, PCI5, P2O5—pyridine, TsCl (with phase-transfer... 

Hussenet, R, Le Goff, R, Sennyey, G. (1996) Two-Step Process for the Preparation of N,N -Disubstituted Carbodiimides by Phosgenation of Disubstituted Ureas. EP 723955 (Soci t Nationale des Poudres et Explosifs, France). 

A first terminal imido complex of nickel (121) was prepared according to Equation (3).468 The synthesis goes via the Ni11 amido compound (122) and uses the steric bulk of the arylimido group for stabilization. The Ni11 center in (121) is planar and three-coordinate. Reaction of (121) with CO or benzyl isocyanide leads to formal nitrene transfer with formation of (124) and (125), respectively. Further reaction with CO liberates the isocyanate and carbodiimide (Equation (4)). 69... 

---