Cyclic homologation

Naphthenes always have higher octane numbers —RON and MON— than their non-cyclic homologs for example, the RON of n-hexane is 24.8 while cyclohexane attains 83. 

The synthesis of poly(phosphazene) derivatives by single or multistep reactions of poly(phosphazene) precursors continues to represent the major pathway to new members of this class of materials. The reaction of an oxyanion with (NPClj) is the most common synthetic procedure in this area. Protected glyceral poly(phosphazenes) analogous to the cyclic homologs, 28, have been prepared and may be crosslinked by exposure to yi radiation. Acidic deprotection yields the free glyceral substituted polymers which undergo slow hydrolysis. The deprotected polymers can be crosslinked using... 

Other substituents, such as the pseudohalo groups (CN, NCO, OCN, NCS, SCN) and carboxyl groups, can be attached to the --C(X)=N— system, and compounds of this type are discussed within the outlined scheme. Likewise, O-substituted derivatives of hydroxamoyl halides are included in Chapter 6. Since the imidoyl halides can be part of a heterocyclic system, the cyclic homologs are treated separately in the last chapter. The fully aromatic compounds, such as halopyridines, halopyrimidines, and halo-1,3,5-triazines, are discussed only briefly in Chapter 8, as their chemistry is somewhat different. 

Chlorothiazoline (XXXV), the cyclic homolog of chlorothio-formimidate, has been synthesized from phenyl isothiocyanate and phosphorus pentachloride ( ), but again nothing is known about its reactivity with nucleophiles. 

Figure 21.18 Elution volume dependence of the molar mass and of the radius of gyration for a linear PS comb L-2-100 (E) and of its cyclic homolog C-2-100 (C). (Reproduced with permission from M. Schappacher and A. Deffieux, Imaging of catenated, figure-of-eight, and trefoil knot polymer rings, Angewandte Chemie International Edition, 2009, 32, 5930-5933. Wiley-VCH Verlag GmbH Co. KGaA.)...

At longer polymerization times, the amount of cyclic homologs (NPCl2) (n>3) slowly increases. Formation of cyclic oligomers (104) may simply proceed by the backbiting process (eqn [56]), as in the cationic polymerization of other cyclic monomers, containing heteroatoms, " ... 

In 1880, Liebermann and Voltzkow (40), and then Voltzkow (41), condensing chloroacetic acid with both ethyl N-phenylthiocarbamate and p-tolylisothiocyanate obtained homologous compounds to which they attributed formulas 40 and 41, whereas their structure probably derives from that of 38 by substituting an aryl group on the cyclic nitrogen. 

Since the -elimination mechanism requires formation of a six-membered cyclic transition state, this reaction is not possible for five- or six-membered lactones, but may be applied to higher homologs. 

The classic method for controlling stereochemistry is to perform reactions on cyclic substrates. A rather lengthy but nonetheless efficient example in the prostaglandin field uses bicyclic structures for this purpose. Bisacetic acid derivative S is available in five steps from Diels-Alder reaction of trans-piperylene and maleic anhydride followed by side-chain homologation. Bromolactonization locks the molecule as bicyclic intermediate Esterification, reductive dehalogen-... 

Diazomethane reacts with ketonic compounds according to the reactions to give epoxides and homologated ketones. If the ketone employed is cyclic, only a single... 

Acetic add, ethylenediaminetetra-, 4,253 add-base equilibria, 2,779 in analysis, 1,522 complexes composition, 2,783 coordination numbers, 2,783 solid state structure, 2,783 cyclic derivatives complexes, 2,785 in electroplating, 6,14 heteroatom derivatives metal complexes, 2, 786 homologs... 

Although the evidence for a cyclic oxide S5O is relatively weak, its existence is likely in the light of the properties of the homologous oxides SsO, S7O, and SsO which show analogous spectra and reactions (see below). 

Various cyclic phosphonate esters 36 and 37 have been described previously as products from the HHT reaction of 25 with the appropriate cyclic phosphite. A complementary method has also been developed from the V-protected phosphonyl chloride 84, which was readily prepared from the corresponding phosphonic acid 83. Subsequent reaction of 84 with the appropriate diol produced the cyclic phosphonate esters 85 (63). Higher homologs of 85 have also been prepared from the analogous propane or butane diols. 

This procedure illustrates a new three-step reaction sequence for the one-carbon ring expansion of cyclic ketones to the homologous tt,/3-unsaturated ketones. The key step in the sequence is the iron(III) chloride-induced cleavage of the central bond of trimethyl-silyloxycyclopropanes which me obtained by cyclopropanation of trimethylsilyl enol ethers. The procedure for the preparation of 1-trimethylsilyloxycyclohexene from cyclohexanone described in Part A is that of House, Czuba, Gall, and Olmstead. ... 

The enantiomeric reduction of 2-nitro-l-phenylprop-l-ene has been studied in a range of Gram-positive organisms including strains of Rhodococcus rhodochrous (Sakai et al. 1985). The enantiomeric purity of the product depended on the strain used, the length of cultivation, and the maintenance of a low pH that is consistent with the later results of Meah and Massey (2000). It has been shown that an NADPH-linked reduction of a,p-unsaturated nitro compounds may also be accomplished by old yellow enzyme via the flcf-nitro form (Meah and Massey 2000). This is formally analogous to the reduction and dismutation of cyclic enones by the same enzyme (Vaz et al. 1995), and the reductive fission of nitrate esters by an enzyme homologous to the old yellow enzyme from Saccharomyces cerevisiae (Snape et al. 1997). 

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