Dicyclohexylcarbodiimide DCC

The most intensively studied oxidizing system is that developed by Pfitzner and Moflatt in which the oxidation is carried out at room temperature in the presence of dicyclohexylcarbodiimide (DCC) and a weak acid such as pyridinium trifluoroacetate or phosphoric acid. The DCC activates the DMSO which in turn reacts with the carbinol to give an oxysulfonium intermediate. This breaks down under mild base catalysis to give the desired ketone and dimethyl sulfide. 

Schemes are available, however, that start from the free carboxylic acid, plus an activator . Dicyclohexylcarbodiimide, DCC, has been extensively employed as a promoter in esterification reactions, and in protein chemistry for peptide bond formation [187]. Although the reagent is toxic, and a stoichiometric concentration or more is necessary, this procedure is very useful, especially when a new derivative is targeted. The reaction usually proceeds at room temperature, is not subject to steric hindrance, and the conditions are mild, so that several types of functional groups can be employed, including acid-sensitive unsaturated acyl groups. In combination with 4-pyrrolidinonepyridine, this reagent has been employed for the preparation of long-chain fatty esters of cellulose from carboxylic acids, as depicted in Fig. 5 [166,185,188] ...

The lithium benzamidinates Li[PhC(NR)2] (R = Cy, Pr ) and Li[2,4,6-(Cp3)3C6H2C(NCy)2] have been prepared analogously. Reaction of FcLi (Fc = ferrocenyl) with 1,3-dicyclohexylcarbodiimide ( = DCC, Scheme 6), followed by addition of water, afforded the ferrocene-substituted amidine Fc(NCy)NHCy in 50% yield. The amidine is readily deprotonated by LLN(SiMe3)2 or NaN(SiMe3)2 to yield the alkali metal amidinates, Li[FcC(NCy)2l and Na[FcC(NCy)2l in high yields. ... 

This carbon-carbon bond-generating reaction can be used extensively over a wide range of chemistries [11]. As the reaction is an equilibrium process, needing the removal of water to obtain high yields, chemical means have to be used to accomplish this task. 1,3-Dicyclohexylcarbodiimide (DCC) is a commonly used reagent for this purpose. Alternatively, molecular sieves find use for conventional processing, but are not so favorable for micro-reactor processing, because the sieve needs to be inserted into the micro channel (additional fabrication expenditure) and may disrupt the liquid transport if EOF is applied. 

Scheme 4.6 Various reactions that recycle dicyclohexylurea (DCU) back to dicyclohexylcarbodiimide (DCC).

The reaction of 5a-bromo-a-tocopherol (46) with amines was further elaborated into a procedure to use this compound as a protecting group Toe for amines and amino acids (Fig. 6.35).62 The protection effect was due to a steric blocking of the amino function by the bulky tocopheryl moiety rather than due to conversion into a non-nucleophilic amide derivative, and the Toc-protected amino acids were employed in the synthesis of dipeptides according to the dicyclohexylcarbodiimide (DCC) coupling method.64 The overall yield of the reaction sequence was reported to be largely dependent on the coupling reaction, since both installation and removal of the... 

The conversion of the polystyrene-supported selenyl bromide 289 into the corresponding acid 290 allowed dicyclohexylcarbodiimide (DCC)-mediated coupling with an amidoxime to give the 1,2,4-oxadiazolyl-substituted selenium resin 291 (Scheme 48). Reaction with lithium diisopropylamide (LDA) and allylation gave the a-sub-stituted selenium resin 292, which was then used as an alkene substrate for 1,3-dipolar cycloaddition with nitrile oxides. Cleavage of heterocycles 293 from the resin was executed in an elegant manner via selenoxide syn-elimination from the resin <2005JC0726>. 

More recently, the esterification of oxadiazolinone 89 by 4-dimethylaminobenzoic acid in dry CH2CI2 in the presence of dicyclohexylcarbodiimide (DCC) was described to afford compound 90 (70%). The structure of the product was based on NMR, IR, and MS spectra <2000JLR545>. No other similar reaction was found. 

Table VIII lists some commonly used activating groups. That most widely in use is dicyclohexylcarbodiimide (DCC), often in conjunction with additives such as A -hydroxysuccinimide (HONSu) or HOBt. These convert the O-acyl isourea intermediate 12 into the N-acyl derivative 13 (Scheme 14), which is less prone to racemization under the experimental conditions. But it must be emphasized that all such chemical methods involve some racemization of asymmetric centers, and the trick is to reduce this to an absolute minimum.

The condensation of DMDP with carbon disulfide/dicyclohexylcarbodiimide (DCC) afforded the indolizine derivative—potentially biological active thionocarbamate on carbohydrate scaffold, fused from the nitrogen side. 

AcOH (step f) and N-acylation with a suitable fatty acid in the presence of 1,3-dicyclohexylcarbodiimide (DCC) (step g) provided the intermediate which after global debenzylation by hydrogenolysis in the presence of palladium on charcoal provided the desired lipid A mimetic (step h). 

Figure 8. SEC profiles of the triblock copolymer precursor ended with carboxyl acid group coupled by SAAP with 1,6-hexamethylenediamine (HMDA) catalyzed by 1,3-dicyclohexylcarbodiimide (DCC) as well as coupled directly in THF as a reference.

---