Conjugation, types

Pyrazole and its 3,5-dimethyl and 3,4,5-trimethyl derivatives combined with two moles of dimethyl acetylenedicarboxylate giving products of similar ultraviolet absorption spectra to the parent pyrazoles. These products [e.g., (69)] do not possess the strong broad absorption at ca. 3.20 /u, characteristic of the bonded N—H group which is present in the parent pyrazoles and are formed by two successive Michael addition reactions. In the case of 3,5-dimethylpyra-zole, the initial fumarate (68) has been isolated and possessed a more conjugated type of absorption spectrum to those of the dipyrazolyl-... 

Novel asymmetric conjugate-type reactions have been accomplished with Cinchona alkaloid-derived chiral thioureas, including less traditional reactions such as asymmetric decarboxylation [71]. In the following discussion, asymmetric reactions involving nitro-olefms, aldehydes and enones, and imines will be highlighted (Fig. 5). 

Fig. 4 Conjugation types in porphyrinoids. Fully conjugated circuits are shaded. For details, see text...

These three conjugation types may correspond to aromaticity or antiaromaticity, in accordance with the Hiickel rule. They can be depicted using the partial resonance structures given in Fig. 4. An additional requirement is that each branch required to participate in cyclic conjugation not contain a formally two-electron heteroatom site (such as -NH-, -O-, etc.) or exocyclic double bonds (such as carbonyl groups). These structural elements are incompatible with Kekule-type canonical structures. Finally, it should be noted that in the case of type C structures macrocyclic conjugation will be preserved, even when one of the a and b branches is not fully conjugated. 

Fig. 6 Conjugation types feasible for various cyclic subunits...

This example confirms the conjugated type of the secondary oxidation reactions under consideration. Meanwhile, the difference between interpretations of the gross equation for the secondary reaction given in Refs [6] and [7] is obvious. 

On this basis, a qualitative criterion in a definite approximation may be applied to complex reactions. This criterion may help in setting a consecutive, parallel or conjugated type of reaction proceeding in the chemical system ... 

Chapter 4 presents experimental data on methane oxidation to formaldehyde with hydrogen peroxide. We shall not discuss them here again, but use them only for determinant D calculation. The calculated D value is 0.2 which, according to currently developed ideas, indicates the conjugated type of CH4 oxidation with hydrogen peroxide. 

Figure 7.20 clearly indicates the conjugated type of two reactions (7.7) and (7.8). In fact, a decline of catalase product (02) accumulation rate is associated with an increasing rate of monooxygenase reaction product yield. These processes interrelate via general reactive intermediate perFTPhPFe3+OOII/AEO,. 

This Chapter will present the actual chromophores of vision, labeled the Rhodonines and derivable from a number of feedstocks, including the retinol family, consist of relatively small molecules with a molecular weight of either 285 (R5 R9) or 299 (R7 R11). They are retinoids of the resonant conjugate type. They are also carboxylic-ion systems and exhibit a negative charge in their fundamental form. The molecules are relatively easily generated in the laboratory in pure form. However, they exhibit a number of unique properties that have made their isolation difficult. They only exhibit the properties of a visual chromophore when in the liquid crystalline state. Their absorption characteristic is a transient one unless a means of de-exciting the molecules of the liquid crystal is present. Finally, they are extremely sensitive to destruction by oxidants and alkali metal ions. 

The fatty acids are either saturated or unsaturated (Table 5-5). The latter acids, especially the polyunsaturated and conjugated types are quite unstable and readily participate in addition reactions or are easily oxidized. Linoleic acid is a common representative together with oleic and linolenic acids. 

Intramolecular conjugate-type addition of the anions of A -[(5)-l-phenylethyl]amides 1 to a,/ -unsaturated esters results in the formation of cyclic acetic acid derivatives 231-33. 

Free sulfilimines are known to undergo conjugate-type addition to electrophilic alkenes to afford aziridines and enamines "1 -1,3. A useful method for the preparation of 16,17starting materials for the synthesis of various compounds with a wide spectrum of physiological activity114, involves the addition of free sulfilimines to ,fi-unsatu-rated oxosteroids. Thus, S,S-diphenylsulfilimine 35 reacts with steroidal cnones (e.g., 34 and... 

Defective excretion of conjugated bilirubin into the bile. This occurs in the Ehibin-Johnson and Rotor syndromes. The resultant hyperbilirubinemia is mainly of the conjugated type as is the hyperbilirubinemia of extiahepatic obstruction of the biliaiy ducts (as by tumor or gallstones). 

The synthesis of model compounds to verify the structures of xenobiotic amino acid adducts (products of nonenzymatic reactions of electrophilic xenobiotics with amino acids In proteins) are Included. Methods for synthesis of some rarely observed conjugate types will be briefly Introduced. The major organic methods for synthesis are exemplified and xenobiotic conjugates prepared via these reactions are tabulated with references to the original publications. 

The sites of location of the hydrolysis of conjugates may vary with animal species, aglycone and conjugate type and, where known, this will be Indicated below. In principle. If hydrolysis does not occur via the action of bacteria In the lumen of the Intestine, It will occur In ... 

Except for the recognized generalizations that glucosides are found in plants and glucuronides are found in animals, it is difficult to establish a consistent correlation of conjugate type and species. 

Conjugation Type Mass Shift Characteristic CNL Polarity of Parent Ion Mass of CNL Reference... 

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