Carboxylic substitution

FIGURE 22.8 Flow rate effect on the elution of polyacrylamide. Degradation of polymer during the analysis occurs in each case at flow rates just above those shown. Unmodified MW = 12-15 x I0 carboxyl substitution = 9.5%. , unmodified A, sheared for 30.0 min , sheared for 12 hr O, sonicated for 1.0 min O, sonicated for 5.0 min. (From Ref 23, Copyright 1988. Reprinted by permission of John Wiley Sons, Inc.)... 

Kim I-B, Dunkhorst A, Bunz UHF (2005) Nonspecific interactions of a carboxylated-substituted PPE with proteins. A cautionary tale for biosensor applications. Langmuir 21 7985-7989... 

In view of the problem of kinetic equivalence it was important to study carboxyl-substituted acetals where bimolecular general acid... 

Rate enhancements are in comparison with the para carboxyl substituted or unsubstituted compounds or corresponding methyl esters. 

An efficient chemical process for closing a diphenylamine is that using palladium(II) acetate (2 mol for substrates carrying electron-withdrawing groups) in acetic acid-methanesulfonic acid. Carbazole formation has been achieved with alkyl-, halo-, nitro-, and carboxyl-substituted diphenylamines. 1-Chlorocarbazole and carbazol-l-yl carboxylic acid as examples were efficiently prepared. - This is probably the best method now available for cyclizing diphenylamines. 

As shown in Figures 1.6b,c, Z and 44C substituents either lower the 2p-spn gap or leave it about the same. In either case, the ground state for Z- or 44C -substituted carbenes is expected to be T. See recent investigations of phenyl carbene, C6H5CH, [164] ethynyl carbene, HC=C—CH [165] carboxylate-substituted carbenes, R—C—C02R [166] and formyl carbene, H—C—C(0)H [167]. 

Where the diene function is attached to or is part of a carbocyclic system, the vinyl cyclopropane formation and subsequent rearrangement affords a reliable approach to the formation of tricyclic carbocycles. Some of the most elegant demonstrations of the use of this methodology in total synthesis of fused cyclopentanoid terpenes come from the work of Hudlicky and coworkers (equations 63-66)90 95"100. In these cases the diazoketones bear a carboxylate-substituted double bond of diene and the intramolecular cyclopropanation requires the combination of CuS04/Cu(acac)2 as catalyst. 

Fujita S, Steenken S (1981) Pattern ofOFI radical addition to uracil and methyl-and carboxyl-substituted uracils. Electron transfer ofOFI adducts with N,N, Ar, Ar -tetramethyl-p-phenylenediamine and tetranitromethane. J Am Chem Soc 103 2540-2545 Fujita S, Nagata Y, Dohmaru T (1988) Radicals produced by the reactions of SO4 with uridine and its derivatives. Studies by pulse radiolysis and y-radiolysis. Int J Radiat Biol 54 417-427 Fujita S, Horii FI,Taniguchi R, Lakshmi S, Renganathan R (1996) Pulse radiolytic investigations on the reaction of the 6-yl radicals of the uracils with Cu(ll)-amino acid complexes. Radiat Phys Chem 48 643-649... 

A systematic review of synthetic approaches to fused azirines is provided in CHEC-III . One of the most common routes to aziridines of this type involves a cyclization via nucleophilic attack of a nitrogen on an exocyclic sp3-hybridized carbon as exemplified in Scheme 1 <2003TL7997, 2003TA1969>. Another general approach to fused azirines involves DielsAlder reactions of carboxylate-substituted 2/7-azirines (e.g., Scheme 2) < 1997S271, 1998J(P1)2969, 2005S555, CHEC-III(1.02.3.2.2)121>. 

Rate enhancements are in comparison with the para carboxyl substituted or unsubstituted compounds or corresponding methyl esters. b Fife, unpublished work. c Bruice and Piszkiewicz, 1967. d Capon et al, 1969. e Fife and Anderson, 1971a, f Anderson and Fife, 1971a, 1973. 

Carboxyl-substituted aminodeoxycellulose (Cell-CH2NH-R-C02H) prepared by the reaction of amino acids with chlorodeoxycellulose adsorbed various heavy metal ions with high efficiency [131]. Cellulose isocyanate reacted with amino acids or their esters in DMSO at low temperature to yield cellulose derivatives containing amino acid residues [60]. These derivatives adsorbed various kinds of metal ions in their free acid state with relatively high... 

Direct reaction of glycine with glyoxal to form a carboxylate substituted imidazole ring results in a zwitterionic species where only one of the two carboxylic acid units is depro-tonated [73,74] (see Figure 6.30). 

Double bonds of enynes act as nucleophiles and for ene-allenes perform similarly. Actually, some of the reactions of enynes with propargylic carboxylate substitution may... 

Plourde [17] has described the radical addition of alkyl, substituted alkyl and benzyl thiols to polymer-supported cychtol allyl ethers. Treatment of immobilized allyl ether 117 with benzyl thiol in the presence of AIBN provided, after base-induced cleavage from the support and purification, sulfide 119 in high yield and purity (Scheme 25). Similar reactions with hydroxyl- and carboxyl-substituted alkyl thiols also resulted in good yields of products as single regioisomers [17]. 

A chiral phosphonate-substituted azirine was prepared and its Diels-Alder reactions studied <20020L655>. Azirine 105 is prepared by the Swern oxidation of the corresponding aziridine as shown in Scheme 18. The Diels-Alder reaction of azirine 105 with Danishefsky s diene provides aziridine 106 in excellent yield as a single diastereomer. Note that the reaction time for azirines such as used by Gilchrist is only 15 min as compared to 8h with the phosphonate substituted azirines suggesting that the carboxylate-substituted azirines are much more reactive than the phosphonate-substituted azirines <19978271, 2001J(P1)2969, 2005S555>. 

Fujita S, Steenken S. (1981) Pattern of OH radical addition to uracil and methyl- and carboxyl-substituted uracils. Electron transfer of OH adducts with N,N,N , N -tetramethyl-p-phenylenediamine and tetranitromethane./Aw Chem Soc 103 2540-2545. 

The carboxyl-substituted dienophile (2) shows excellent stereoselectivity with cyclopentadiene, affording solely exo adduct (9) (equation 3). This somewhat surprising result can be rationalized if one assumes that the cycloaddition involves an ( )-imine which reacts via a transition state having the bulky tosyl group endo to avoid steric interactions with the methylene bridge of the diene. Such a transition state, however, precludes secondary orbital interactions of the carbonyl group with the diene. 

In addition to the many ring-synthetic procedures which give carboxyl-substituted products, there is also a variety of other methods which can be applied to the preformed rings. Oxidation of an alkyl group is an obvious... 

Ring-synthetic procedures which lead to carboxyl-substituted imidazoles are usually multistep and seldom give high yields. Nevertheless, they are frequently the only viable routes to products with a particular substitution pattern. A summary of the methods available follows. 

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