Pseudo high dilution

Cyclic aryl ether ketones have been prepared from l,2-bis(4- uoroben2oyl)ben2ene and bisphenols under pseudo high dilution conditions. These materials undergo ring-opening polymeri2ation in the presence of an anionic catalyst (87). 

A slightly different variation on this concept was developed by Crosby, who used a polymer for selective activation of one alcohol for a supported sulfur based mono-oxidation of heptanediol (Scheme 2.10) [30]. Here the reactant interacts with the support directly (under pseudo high dilution), becoming chemically transformed in the process. 

These sulfur-containing macrocycles had been prepared under pseudo-high dilution conditions, but Hay and coworkers demonstrated that the cyclodepolymerization of aromatic disulfide polymers was an efficient and easier... 

The process for preparing macrolactones described in the text is impractical. Instead of this process one uses a continuous method with a syringe pump a solution of the hydroxycar-boxylic acid is added very slowly—that is, in the course of hours or days—i nto a small flask, which contains > 1 equivalent of the activator and, if necessary, just enough triethylamine to neutralize any released HC1. The rate at which the acid is added is regulated such that it is equal to or smaller than the lactonization rate. This is called pseudo high dilution. At the end of the reaction the lactone solution can be relatively concentrated, e. g., 10 mmoEL, at least 10,000 times more concentrated than without the use of this trick. 

Pyrrole-substituted a,co-diamines 517 varying in length and number of heteroatoms between the amine functionalities were obtained from the corresponding acid and appropriate diamine under standard amide-forming conditions in yields of 18-70%. The amines 517 were reacted with l,l -ferrocenedimethanol 518 under pseudo high-dilution conditions to form 7 r 7-ferrocenes 519, the macrocyclic anion receptors, in 20-35% yields (Equation 122) <2001JOM(637)343>. 

Synthesis of cyclic oligomers of PEK under pseudo-high-dilution conditions... 

H. Zhang, X. Wang, J. Li, and F. Wang, Facile synthesis of polyaniUne nanofibers using pseudo-high dilution technique, Synth. Met., 159, 1508-1511 (2009). 

Reagents and conditions (i) CuCij, CuCi, pyridine, RT, pseudo high-dilution. 

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