Alternating Polyheterocycles

The purpose of this section is to highlight the applications of microwave irradiation to multistep synthesis of polyheterocyclic systems with potent pharmaceutical value. When conventional thermal procedures (metal or oil bath) fail, and irrespective of the conditions needed in the homogeneous phase, microwave irradiation can be used as an alternative to classical methods enabling development of easy and rapid access to new heterocycles. 

Poly (thiophene)s are of particular interest as electfochromic materials owing to their chemical stability, ease of synthesis and processability. For the most part, current research has been focused on composites, blends and copolymer formations of several conjugated polyheterocyclics, polythiophene and its derivatives, especially PEIX)T. In one example, poly(3,4-ethylenedioxythiophene) (PEDOT)/poly(2-acrylamido-2-methyl-l-propanesulfonate) (PAMPS) composite films were prepared by Sonmez et al. for alternative electrochromic applications [50]. Thin composite films comprised of PEDOT/PAMPS were reported to switch rapidly between oxidized and neufial states, in less than 0.4 s, with an initial optical contrast of 76% at A.max. 615 nm. Nanostructured blends of electrochromic polymers such as polypyrrole and poly(3,4-ethylenedioxythiophene) were developed via self-assembly by Inganas etal. for application as an electrochromic window [26]. Uniir etal. developed a graft-type electrochromic copolymer of polythiophene and polytetrahydrofuran for use in elecfiochromic devices [51]. Two EDOT-based copolymers, poly[(3,4-ethylenedioxythiophene)-aZ/-(2,5-dioctyloxyphenylene)] and poly[(3,4-ethylenedioxythiophene)-aft-(9,9 -dioctylfluorene)] were developed by Aubert et al. as other candidates for electrochromic device development [52],... 

MSubstituted-2-pyridones can be used as substrates for ring closure to a number of polyheterocyclic systems, as an alternate to the Pschorr cycliza-tion Of to the cyclizations of the corresponding At-alkyl-2-halopyridinium halides. 2-Substituted pyridines (MI-625 X =C1, Br, OC Hj) and 3-(2-bromo-ethyl)indole give -[2-(3-indolyl)ethyl]-2-substituted pyridinium bromide... 

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