DCC producing

Condensation of 4,4-dithiobis(benzoic acid) (38) [52] with diethyl L-glutamate in the presence of DCC produced (39), from which (40) was readily obtained by reduction with sodium borohydride [53] (Scheme 3.7). 

The most difficult total syntheses in this class of pseudotrisaccharides were those of streptomycin and dihydrostreptomycin. About 35 years after their discovery and the elucidation of their structure, S. Umezawa and colleaguessucceeded in synthesising these compounds. The glycosyl derivative (I), prepared through several steps from streptobiosaminide, was condensed with the protected streptidine (II), to yield dihydrostreptomycin, after deprotection. Subsequent oxidation with DMSO/dicyclo-hexylcarbodiimide (DCC) produced streptomycin... 

The principal producers of lead chromate pigments ia North America are Cookson, DCC (owned by Kikuchi), Engelhard, and Wayne Pigment. In Europe, lead chromates are produced by Ciba ia Holland, CapeUe ia Erance, and Heubach GmGH ia Germany. 

HCO2H, DCC, Pyr, 0°, 4 h, 87-90% yield. These conditions produce N-formyl derivatives of r-butyl amino acid esters with a minimum of race-mization. -... 

An improved FCC unit is the deep catalytic cracking unit (DCC) that is designed to produce gasoline from vacuum gas oil (VGO). The... 

In the presence of DCC, 140 is allowed to react with both l-hydroxy-5-nitroindole (36) and 1-hydroxy-1,2,3-benzotriazole (141). Interestingly, their corresponding active esters, 142 and 143, are obtained in excellent yields as stable crystalline compounds. Both compounds are found to react with variety of nucleophiles, such as alcohols and amines, to produce 144 and 145 in good to excellent yields, as can be seen from the typical examples shown in Scheme 22 (2001H2361). As aresult, it becomes possible to produce various kinds of derivatives of wasabi phytoalexin utilizing 142 and 143. 

Deep catalytic cracking (DCC) is a catalytic cracking process which selectively cracks a wide variety of feedstocks into light olefins. The reactor and the regenerator systems are similar to FCC. However, innovation in the catalyst development, severity, and process variable selection enables DCC to produce more olefins than FCC. In this mode of operation, propylene plus ethylene yields could reach over 25%. In addition, a high yield of amylenes (C5 olefins) is possible. Figure 3-7 shows the DCC process and Table 3-10 compares olefins produced from DCC and FCC processes. ... 

First, the acid anhydride is produced by the reaction of the free acid with DCC. NucleophiUc attack by 4-pyrroUdinonepyridine on the anhydride results in the corresponding, highly reactive acylpyridinium carboxylate this leads to the formation of cellulose ester, plus a carboxylate anion. The latter imdergoes a DCC-mediated condensation with a fresh molecule of acid to produce another molecule of anhydride. N,N-carbonyldiimidazole (CDl) may substitute DCC for acid activation, the intermediate being N-acyhmidazol,... 

With DMSO Based Reagents. An alcohol is treated with DMSO, DCC, anhydrous phosphoric acid in what is called Moffatt oxidation. In this way, a primary alcohol can be converted to the aldehyde with no carboxylic acid being produced. 

Number of Polymer Chains. The quasiliving character of IBVE polymerization is further supported by quantitative analysis. Figure 4 illustrates changes in N, the number of poly(IBVE) chains produced per unit initiator (j>-DCC), as a function of WjbvE N is defined by eq. 2 ... 

The linear Mjj versus Wjj e plots imply that the number of poly(MVE) chains produced per unit initiator, N (cf. eq. 2), is constant during the polymerization. The absolute values of N were greater than unity (2.50 and 2.79 at [p-DCC]0 = 1.0 and 2.0 mM, respectively), suggesting that chain transfer to monomer may have occurred during the early stages of the polymerization. 

It has been known for years that the activated residues of acyl- and peptidylamino acids enantiomerize during coupling (1.9). However, the racemization tests available (see section 4.9) did not allow for a valid comparison of the tendency of residues to isomerize because they incorporated a variety of aminolyzing residues and N-substituents. Valid demonstration of the different sensitivities of residues was provided by classical work on the synthesis of insulin. It was found that a 16-residue segment with O-tert-butyltyrosine at the carboxy terminus produced 25% of epimer in HOBt-assisted DCC-mediated coupling in dimethylformamide, and the same segment with leucine at the carboxy terminus produced no epimer. Only when series such as Z-Gly-Xaa-OH coupled with valine benzyl ester became available was it possible to compare many residues with confidence. Unfortunately, it transpires that the issue is extremely complex. 

With these selected examples as context, it became clear to several laboratories in the mid-1990s that one should be able to combine reversible formation of compounds (exchange processes) and a selection method with the then rapidly developing field of combinatorial chemistry to produce equilibrating libraries that would evolve based on some selection process. Thus, dynamic combinatorial chemistry or DCC, as it came to be called, evolved from a number of lines of research into the diverse and vibrant field it is today. 

Metal-catalyzed allylic substitution reactions have been a mainstay of synthetic chemistry because of their ability to proceed irreversibly and with high selectivity [42]. It is also feasible, however, to produce analogous systems that are completely reversible and nonselective, or ideally situated for use in DCC. These are essentially metal-catalyzed transesterification reactions, with the added feature of potentially providing stereochemical scrambling (and selection) as well as constitutional variation. An early example of this was provided in 2000 by Kaiser and Sanders [43]. In the absence of a template, reaction of diallyl diacetate 22 with a dicarboxylic acid in the presence of catalytic Pd(0) produced a negligible amount of the cycfized compound 23 (Fig. 1.9). However, when templated with 1,3-bis(4-pyridyl) benzene, yield of the cyclic structure increased to roughly 10%, independent of the dicarboxylic acid used. 

Industries [3], Six other DCC units are in operation with a total operating experience of more than 50 years. Total licensed capacity is about 20 MMTA. Two major grassroots units currently under construction were licensed to the joint venture of Saudi Aramco Sumitomo, and to JSC Taneco, Nizhnekamsk, to produce polymer grade propylene as shown in Table 8.2. In addition, RIPP Sinopec recently licensed three DCC units in China and Shaw licensed two DCC units in India. 

Intramolecular cyclization of 6-(mesyloxymethyl)bicyclo[4.4.0]dcc-l-cn-3-one using lithium diiso-propylamide produced almost exclusively the y-alkylation product tricyclo[5.3.1.01,6]undec-5-en-4-one (17), together with a trace amount of the 2-alkylation product tricyclo[5.3.1 016]undec-5-en-8-one (18).17 Surprisingly, the a-alkylation product 18 was the major product when the cyclization was carried out using potassium tert-butoxide.17 The preference for y-alkylation over a-alkylation can be rationalized by the Hammond postulate which favors y-alkylation due to the less reactant-like transition state when lithium diisopropylamide is used. Alternatively, when potassium /ert-butoxide and 18-crown-6 in hexamethylphosphoric triamide is used, the reactivity of the enolate anion is significantly enhanced. As a result, the transition state becomes reactant-like so that a-alkylation is the predominant process.17... 

Primary alkyl halides (chlorides, bromides, and iodides) can be oxidized to aldehydes easily and in good yields with dimethyl sulfoxide.311 Tosyl esters of primary alcohols can be similarly converted to aldehydes,312 and epoxides313 give a-hydroxy ketones or aldehydes.314 The reaction with tosyl esters is an indirect way of oxidizing primary alcohols to aldehydes (9-3). This type of oxidation can also be carried out without isolation of an intermediate ester The alcohol is treated with dimethyl sulfoxide, dicyclohexylcarbodiimide (DCC),315 and anhydrous phosphoric acid.316 In this way a primary alcohol can be converted to the aldehyde with no carboxylic acid being produced. 

An efficient synthesis of ( )-quebrachamine is based on the construction of a suitable precursor via ring cleavage of an a-diketone monothioketal (810) (80JCS(P1)457). This monothioketal, available from 4-ethoxycarbonylcyclohexanone ethylene ketal, was fragmented to the dithianyl half ester (811) with sodium hydride in the presence of water. Reaction of (811) with tryptamine and DCC provided an amide which was converted to the stereoisomeric lactams (812) on hydrolysis of the dithiane function. Reduction of either the a- or /3-ethyl isomer with lithium aluminum hydride followed by conversion of the derived amino alcohol to its mesylate produced the amorphous quaternary salt (813). On reduction with sodium in liquid ammonia, the isomeric salts provided ( )-quebrachamine (814 Scheme 190). 

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