Carbodiimides applications

Homoleptic lanthanide(III) tris(amidinates) and guanidinates are among the longest known lanthanide complexes containing these chelating ligands. In this area the carbodiimide insertion route is usually not applicable, as simple, well-defined lanthanide tris(alkyls) and tris(dialkylamides) are not readily available. A notable exception is the formation of homoleptic lanthanide guanidinates from... 

Since the pressure build up is primarily due to the evolution of CO as MDI is being decomposed to carbodiimide, the thermodynamic relationship PV = nRT may be applied to convert the pressure profiles to plots of moles of CO2 generated vs. time. This is shown for the 225 °C isotherm in Figure 3. The theoretical curve obtained through the application of zero-order kinetics is also shown in this plot and the data seem to be well accommodated by this rate law throughout the majority of the run. 

Smith, M., Moffatt, J.G., Khorana, H.G. (1958) Carbodumides. VIII. Observations on the Reactions of Carbodiimides with Acids and Some New Applications in the Synthesis of Phosphoric Acid Esters. Journal of the American Chemical Society, 80, 6204-6212. 

Synthetic studies in this area have thus concentrated mainly on routes to indolonaphthyridines. A widely applicable route, leading to various indolo[2,3- ]naphthyridines, for example, 5-7, and aza-analogues such as 8, involves the reaction of an o-alkynylaryl isocyanate, for example, 4, with a pyridyliminophosphorane, followed by thermolysis of the resulting carbodiimide (Scheme 1) <2000JOC7977, 2002JOC5412>. 

CMC should be able to participate in the two-step reaction using a sulfo-NHS ester intermediate similar to EDC, however there are no reports in the literature to this effect. Protocols for the use of this reagent in biological crosslinking applications should be essentially the same as those given previously for EDC, except substituting a molar equivalent quantity of CMC. See Sections 1.1 and 1.2 in this chapter for additional information concerning carbodiimide reactions. 

Preparation of carbodiimides by dehydration of the corresponding ureas is of general applicability and is well adapted to the laboratory preparation of substantial quantities. The intermediates for this particular preparation are commercially available at moderate cost. 

Supported reagents have found application in many areas of synthesis including the construction of small peptides, the traditional foundation stone of solid phase synthesis. For example a recent paper describes the preparation of dipeptide p-nitroanilide and phosphonate libraries by supported carbodiimide coupling and scavenger purification (Scheme 2.52) [79]. 

ROMP polymers bearing acid chloride, phosphonate, carbodiimide, phosphonyl chloride, and phosphine groups have been used as platforms in phase-switching, sequestration, capture-release, and soluble support applications. 

Title Macrocyclic Carbodiimides (MC-CDI) and Their Derivatives, Syntheses, and Applications of the Same... 

Since depsipeptides, in contrast to classical peptides, contain units constructed from amino and hydroxy acid residues, the various methods for their preparation are generally pathways involving the formation of ester bonds. The novel achievements in this area discussed (vide infra) are associated with further developments in the mixed anhydride technique, the application of effective catalysts in the carbodiimide procedure, and adaptation of the known Mitsunobu reaction to the depsipeptide case. A number of significant and efficient esterification procedures utilized for the preparation of depsipeptides are considered. 

The carbodiimide method has been employed in several syntheses of depsipeptides. However, direct application of DCC for the formation of the ester bond between the amino acid and hydroxy acid components under the usual conditions of amide coupling affords the desired depsipeptides in acceptable yields only in the case of unhindered co-hydroxy units [54] or an active hydroxy group, such as in TV-benzoyl-u-hydroxyglycine benzyl ester. For example, Ravdel et al.[55 have performed the esterification of various benzyloxycarbonyl- and phthalylamino acids with /V-benzoyl-a-hydroxyglycine benzyl ester with DCC in 50-65% yield. On the other hand, Shemyakin et all21 failed to obtain the expected depsipeptide products on condensation of bulky benzyloxycarbonyl- or phthalylvaline with a-hydroxy-isovaleric acid benzyl ester. The main product was acylurea in the first case and phthalylvaline anhydride in the second. Thus, the classical carbodiimide procedure could not be applied in practical depsipeptide preparation. 

In situ generated acyllithium reagents not only can acylate ketones, but also can acylate aldehydes,3 esters,4 lactones,5 isocyanates and isothiocyanates,6 carbodiimides,7 carbon disulfide and carbonyl sulfide,8 organic disulfides,9 and trialkylchlorosilanes.10 For reviews, see references 11 and 12. This direct, nucleophilic acylation procedure, when applicable, makes unnecessary the usually... 

Since the most common group of 1,3-diazocines is related to cyclic urea 104 (called, for example, perhydro-l,3-diazocine-2-one or N,N -pentamethyleneurea), a separate section is devoted to the synthesis, chemistry, and applications of 104, substituted 104, and related molecules such as thiourea 105, guanidines 106, and carbodiimide 107. 

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