Effect of Ring Substitution

Among the heterocyclic derivatives, carbazole ring has emerged as a vital building block in the synthesis of many useful optoelectronic materials.93-96 

---

In a time course study on the conversion of ( )-l-phenylethanol 13 (X=H), formation of acetophenone was observed to a maximum of around 20% during the conversion of (S)- to (R)- alcohol which occurred over 24 h to give (R)-13 in 96 % yield, 99% e.e. The effect of ring substitution on the efficiency of the dera-cemization was notable. While para substituents (Cl, OMe, Me) gave good results, ortho derivatives could not be deracemized and the biocatalyst showed little activity towards meta substituted compounds. On addition of allyl alcohol, improvements in e.e. were obtained, particularly for the conversion of l-(m-methylphenyl)ethanol (from 21 to 94% e.e.). However these improvements did appear to be at the expense of yield (89% diminished to 55%). The authors sug-... 

Tables. Effect of % Ring Substitution on Rate of Reaction of 1-Bromooctane in Toluene with Cyanide Ion at 90 °C 89)...

The effect of ring substitution on the O-ncophyl rearrangement of 1,1-diarylalkoxyl dadicals has been reported.174... 

The constant current electrolysis of methyl eugenol serves to illustrate some of the effects of ring substitution and electrolyte on the course of such reactions. When carried out in methanol containing 2% NaOH or KOH (with or without added NaC104), an approximately 1 1 mixture of or// o-quinone bisketal (LXVI) and para-quinol ether (LXVII) was obtained. In contrast, when the oxidation was carried out in methanol-NaC104 in the absence of base, only side-chain substitution product (LXVIII) was obtained [Eq. (33)] [77]. This work clarified an earlier mechanistic interpretation of the reaction [78]. 

Itano HA, Hollister DW, Fogarty WM, Jr, et al. Effect of ring substitution on the hemolytic action of arylhydrazines. Proc SocExp Biol Med. 1974 147(3) 656-658. 

Campo, C.J. Anastasiou, T. Uhrich, K.E. Polyanhydrides. The effects of ring substitution changes on polymer properties. Polym. Bull. (Berlin) 1999, 42 (1), 61-68. 

C Netto-Ferreira, IGl Avellar, and 1C Scaiano. Effect of Ring Substitution on the Photochemistry of (X-(Aryloxy)acetophenones. J Org Chem 55 89-92, 1990. 

The effects of ring substitution and the effect of aromatic quenchers on the photoreduction by toluene of a,a,a-trifluoroacetophenone have been presented. The results are interpreted in terms of differing reactivities of the nn and n,n triplets. 

The isomers of DDT illustrate the effects of ring substitution on biological activity. Large differences in activity also exist in cis-trans isomers, which are given for two organophos-phate insecticides in Table 29.6. Optical isomers of pesticidal compounds also exhibit differences in biological activity. This difference is exhibited in the activity of pyrethrpids and in the isomers of benzene hexachloride, where the isomer lindane possesses almost all the useful insecticidal activity of the compound. 

---