Substituted Monocyclic Compounds

Nitration of monocyclic compounds is summarized in Table 4. Substitution occurs in the expected positions. The reaction conditions required are more vigorous than those needed for benzene, but less than those for pyridine. Ring nitration of oxazoles is rare, but (114) has been obtained in this way (74AHC(17)99). 

Various heterocyclic structures, among them 3-substituted-hexahydro-277-pyrimido[l,2- ]pyrimidin-2-ones 190, have been prepared by solid-phase synthesis. The acetates 187 were reacted with diaminoalkanes, the resulting diamines 188 cyclized with BrCN to the monocyclic compounds 189, which were cleaved and cyclized with Et3N to give 190 (Scheme 30) <2005TL5289>. 

Parent monocyclic Polycyclic derivatives OH-Substituted derivatives NH2-Substituted derivatives compounds... 

Monocyclic l,2-dihydro-l,2-azaborines (3) easily form polymers with the exception of the 2-phenyl derivative (109 R = Ph), probably because of interaction between the two rings. In contrast, the alkyl substituted monocyclic system (155) is stable towards polymerization although it is easily oxidized by air and hydrolyzed by water. This stability order between (3) and (155) was predicted by semi-empirical methods. However, the ring system (7), isosteric with pyridine, seems to be the most stable of the monocyclic systems. Some of its alkyl derivatives remain unchanged after 50 h in concentrated sulfuric acid at 80 °C. After reflux in 1M sodium hydroxide almost all of the compound was recovered. 

Some interesting results were obtained by comparative investigation of the infrared (IR) spectra of quinuclidine, -substituted piperidines, and piperazines.27 Monocyclic compounds gave at 2700-2800 cm-1 characteristic absorption bonds attributable to interaction between the nitrogen lone-pair electrons and the neighboring axial CH bonds. Quinuclidine does not absorb in this region, probably because of the absenceof such interaction in the quinuclidine ring. There are absorption bands characteristic of quinuclidine at 2430, 2915, and 3405 cm"1.28... 

The generation of the condensed anhydro-5-aminooxazolium hydroxide (301) is described in Section 4.18.3.1.5(iii). Monocyclic compounds of this type are produced in a similar manner from IV-substituted acylaminoacetonitriles (equation 155). 

The results in Figure 1 can be interpreted in terms of general ring structures with the hydrocarbon classes. The peak for the polypolar aromatic fraction at 160° C probably is caused by polar-monocyclic compounds and the peak at 240° C is probably the result of polar dicyclic compounds. The broad curve in the monoaromatics centering at 275°C is probably mainly caused by alkyl-substituted tetralins while the peaks... 

Monocyclic compounds Polycyclic derivatives OH-substituted derivatives NH substituted derivatives ... 

The azido olefins 117 and 120 were cyclized to the triazolines 118 and 119 in excellent yields <2001TL9175>. This is an interesting process in that the intermediate triazolines are isolated and then photolytically decomposed to aziridines 119 and 122 in very good yields (Scheme 19). All of these aziridines were reported to be stable compounds especially to acidic conditions. This is significant in that previous examples of silyl-substituted monocyclic aziridines were quite unstable undergoing acid-catalyzed rearrangements. 

The stereochemistry of decomposition of monocyclic pyrazolines is more complicated still. It is not appropriate to discuss this work here since most of it was conducted on alkyl-substituted, unlabeled compounds, but the interested reader is referred to the paper by Bergman for a thorough experimental study and a good review of earlier work. 

The cleavage activity of the monocyclic compounds listed in Scheme 19.8 against DNA is generally only moderate, with EC50 around 500 pM and with D/S ratios <1 15. In order to increase the potency, the hydroxy substituted derivatives 30 and 35 have been extensively used for the preparation of conjugated compounds where a DNA complexing subunit is attached to the OH group. 

The kinetics of the reactions of many xenobiotics with hydroxyl and nitrate radicals have been examined under simulated atmospheric conditions and include (1) aliphatic and aromatic hydrocarbons (Tuazon et al. 1986) and substituted monocyclic aromatic compounds (Atkinson et al. 1987c) (2) terpenes (Atkinson et al. 1985a) (3) amines (Atkinson et al. 1987a) (4) heterocyclic compounds (Atkinson et al. 1985b) and (5) chlorinated aromatic hydrocarbons (Kwok et al. 1995). For PCBs (Anderson and Hites 1996), rate constants were highly dependent on the number of chlorine atoms, and calculated atmospheric lifetimes varied from 2 days for 3-chlorobiphenyl to 34 days for 2,2, 3,5, 6-pentachlorbiphenyl. It was estimated that loss by hydroxylation in the atmosphere was a primary process for removal of PCBs from the environment. It was later shown that the products were chlorinated benzoic acids produced by initial reaction with a... 

Like other phenoloxidases, this enzyme has a low substrate specificity and is able to ortho-hydroxylate a whole range of para-substituted monocyclic phenols. The catechols produced belong to groups of fine chemicals and pharmaceuticals [66L Furthermore, also bi- and tri-cydic phenols were converted into catechols (Figurel6.3-12) [67] 2-Aminotetralines, on the basis of their dopaminergic properties, are compounds of pharmaceutical interest. 

Baeyer-Villiger oxidation is also a common feature during the catabolic degradation of a variety of other compounds, including monocyclic, bicyclic or polycyclic molecules. For monocyclic compounds, one of the first reports describing formation of a lactone from racemic a-substituted cyclopentanone by various Pseudomonas sp. was by Shaw1341. This could be regarded as the first indication that these reactions were to prove of interest for asymmetric synthesis since the lactone product displayed some optical activity (Fig. 16.5-6). 

In addition to phenols, naphthols, their alkyl derivatives and the heterocyclic compounds mentioned above, a large variety of substituted monocyclic as well as condensed phenols have been subjected to the Reimer-Tiemann reaction. Although with a few exceptions the yields are only moderate, the facile reaction conditions, at least on a laboratory scale, have assured the reaction a permanent place among the variety of methods by which an aldehyde group can be attached to an aromatic nucleus. For example, phenolphthalein (1) has been formylated under standard Reimer-Tiemann conditions by van Kampen to yield the o-hydroxy aldehyde in 59% yield (equation 5)."... 

X-ray crystallographic data are also available for 1,2,3-benzotriazines 3 and 12 15 and other condensed 1,2,3-triazines 16-19. Since a structure determination of the unsubstituted or alkyl-substituted 1,2,3-benzotriazines is not yet available, comparison with the monocyclic compounds is not possible. 

The Hantzsch-Widman system is well suited for the naming of saturated monocyclic compounds. Bridged ring systems, however, present a special challenge, and here the replacement system is preferred. An example is provided by the framework of the bicyclic hydrocarbon norbornane. Heteroatoms may in principle be substituted for any of the carbons. To illustrate, nitrogen substitution at position 7 would give rise to the name 7-azanorbomane. 

It is clear that the construction of appropriately substituted monocyclic P-lactams has attracted great attention not only in the monobactam field, but also in the penem and carbapenem area of antibiotics. Since methods for the construction of the -lactam ring are now abundant, the main difficulties involved are primarily the stereocontrol and the instability of the final product. Although the carbene insertion reaction developed by the Merck group seems to be the most efficient route for the construction of the bicyclic ring system, the development of new procedures, specially for industrial applications, is desirable. It is beyond the scope of this article to provide a comprehensive account of all types of P-lactams appeared in the literature which, perhaps, in some cases could be used as carbapenem building blocks. On the other hand, it has been the purpose of this work to deal with those monocyclic P-lactams, which upon further elaboration, lead to PS-5 and PS-6 carbapenems and related compounds by established protocols. Less emphasis has been put on thienamycin because an excellent review on this subject has recently been published. I wish to apologise... 

The four bases commonly found in RNA are divided into two classes The monocyclic compounds cytosine and uracil are called pyrimidine bases because they resemble substituted pyrimidines, and the bicyclic compounds adenine and guanine are called purine bases because they resemble the bicyclic heterocycle purine (Section 19-3). 

The optimised conditions were then applied to a range of cyclic a-alkyl and a-benzyl substituted P-keto allyl esters to generate the corresponding a-tertiary ketones in good yields and excellent enantioselectivities. Interestingly the fused aromatic substrates such as tetralone 102 gave the opposite sense of stereoinduction in the resulting tertiary product (105), compared to the monocyclic compounds such... 

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