Modification of the Aromatic Ring

Table 2 summarizes some of the transformations of substituents which have been carried out on azetidines without effect on the ring <79CRV33l). Other transformations of interest are the base catalyzed epimerization, H exchange and alkylation of the activated H-3 in azetidines (26) (69JHC153) and the nitration, reduction, diazotization and hence further modification of the aromatic ring in 3-phenyl-fV-acetylazetidine (27) (61LA 647)83). 

Judka and Makosza (Judka and Makosza, 2006, personal communication) have also shown that phenyl sidfones with very simple modifications of the aromatic ring may conveniently be used in the direct olefination reaction (Scheme 82, Table 23). 

Several modifications of the aromatic rings on the N atoms as well as of the C3 spacer of the classical McConville complex have been explored.1075,1076 While the 89/[Ph3C][B(C6F5)4]/AlBu 3 catalyst yields PE with high activity, 3 x 102 gpK (mmol M)-1 h-1 bar-1, the catalyst 88/MMAO gave only moderate activity (15 g (mmol M)-1 h-1 bar-1 at room temperature).1075 Similarly, poor activity was reported for 90/MAO, as well as for the Zr and Hf analogs.1076... 

Biological activity in this series shows considerable tolerance for modification in the ester moiety as well. Esters in which one of the aromatic rings is fully reduced still show good anticholinergic activity. One such agent, propenzolate (66), is prepared by displacement of halogen from N-methyl-3-chloropiperidine (64) by the sodium salt of acid... 

Sherrington et al. were the first to attempt the synthesis of chiral polymeric metal complexes by the chemical modification route,78,177,178 whereby the [Mn(salen)Cl] units are attached in a pendant fashion, by only one of the aromatic rings, to poly(styrene) or poly(methacrylate) resin beads of various morphology. Epoxidation of 1-phenylcyclohexene gave enantioselectivity values between 61% and 91%. 

---