Polyheterocycles

May be used for disubstituted, polyheterocyclic, and polynuclear systems if deviations due to steric and mesomeric effects are allowed for. 

Polyheterocycles. Heterocychc monomers such as pyrrole and thiophene form hiUy conjugated polymers (4) with the potential for doped conductivity when polymerization occurs in the 2, 5 positions as shown in equation 6. The heterocycle monomers can be polymerized by an oxidative coupling mechanism, which can be initiated by either chemical or electrochemical means. Similar methods have been used to synthesize poly(p-phenylenes). 

Another important factor affecting the electronic properties is the steric barrier to planarity along the polymer chain. Since polyheterocycles and polyarylenes must adopt a planar geometry in the ionized state to form quinoid-like segments, steric factors that limit the ability of the polymer to adopt geometries which are planar with respect to adjacent rings have a detrimental effect on the electronic properties (181). 

Fuel cell technology probably offers a new emerging area for polyheterocyclic polymers as membranes. Fuel cells are interesting in transport applications and are now being evaluated in Chicago in transit buses with a 275-hp engine working with three 13 kW Ballard fuel cell stacks. 

Poly (glycolic acid) (PGA), 41, 42, 85 preparation of, 99 Polyheterocyclization concept, 265 Poly(hexafluorobisphenol-A), 361 Poly(hexamethylene adipamide), 5 Poly(hexamethylene adipate), 5 Poly(hexamethylene fumarate) synthesis, 100-101... 

Lautens and coworkers [9] ultimately used this approach to prepare a multitude of different polyheterocyclic ring systems 4-29, using 4-20 and 4-28 as substrates (Table 4.1). Unsymmetrical tethered bisfurans and acetylene dicarboxyclic acid derivatives have also been used in this domino process to allow the formation of three new rings with up to six stereogenic centers. 

Pyrazolopyridopyrimidine-containing polyheterocycles have been prepared by two routes, by formation of either the six- or the five-membered ring this is illustrated by the two syntheses of compound 469 (Scheme 106)... 

Among polyheterocyclic systems, coumarins are synthesized by many routes, including the Pechmann reaction, which involves condensation of phenols with /fke-toesters [51]. This reaction, which has been the most widely applied method, has re-... 

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. 

The nitration of the polyheterocyclic compound 226 leads to the formation of moisture-sensitive nitration products, which undergo further oxidation to give o-quinone-like species (Scheme 55) <1996JOG1898>. 

Using nitrile oxides, various compounds and materials possessing valuable properties have been prepared. Among them are thin-film resistors useful for a thermal head and comprising a nitrile oxide, ruthenium and oxygen, a method for manufacturing the resistor by coating or deposition (529), isoxazole and/or isoxazoline polyheterocyclic systems like 458, which are useful for development of a new class of ionophores (530). 

Several polyheterocyclic compounds containing a condensed 1,2,4-triazole nucleus, such as 3,5-disubstituted thiazolo [2,3-r][ 1,2,4] triazoles, are thermostabilizers for polypropylene and polycaproamide <2003MI2>. Triazolo[3,4-A][l,3]benzothiazoledicarbonitrile derivatives are used to prepare hexazocyclanes-fluorophores as active media for liquid and solid lasers, scintillators, and for transformation of short-wave radiation to long-wave radiation <2004RUP2238276>. 

Triazines have been the subject of a recent and highly documented review <2004SOS(17)223>. Due to the great biological interest of these polyheterocycles, their synthesis has long been an area of intense development, and still constitutes to be an active domain from the academic and industrial points of view. 

There is a large potential for conducting polymers as corrosion-inhibiting coatings. For instance, the corrosion protection ability of polyaniline is pH-dependent. At lower pH polyaniline-coated steel corrodes about 100 times more slowly than noncoated steel. By comparison, at a pH of about 7 the corrosion protection time is only twice for polyaniline-coated steel. Another area of application involves creation of solid state rechargeable batteries and electrochromic cells. Polyheterocycles have been cycled thousands of times with retention of over 50% of the electrochromic activity for some materials after 10,000 cycles. IR polarizers based on polyaniline have been shown to be as good as metal wire polarizers. 

This methodology was further developed in an elegant manner by Padwa and coworkers (61). Combined with a subsequent desulfurization reaction, the method was successfully applied toward the synthesis of complex polyheterocyclic systems related to alkaloid skeletons. For example, the reaction of 94, obtained from... 

Over the past decade, considerable effort has been expended on the design and synthesis of nonpeptidic antagonists for the three receptors (NKl-3) to which SP, NKA, and NKB bind. These antagonists could have therapeutic use in conditions such as migraine, arthritis, inflammatory diseases such as cystitis, psoriasis, asthma, anxiety, depression, and emesis (vomiting). A variety of NKl-3 receptor antagonists have been designed and synthesized. The majority of these compounds are polyheterocyclics. 

Originality Biphenyl-based polyheterocyclics are unreported in the patent literature. 

Observations High-molecular-weight polyheterocyclics were prepared by Suzuki... 

Table 2. Thermal activation energy of conductivity Ed, edge energy of the electronic absorption spectra Eopl, and optical activation energy of photoconductivity Ea/2 for some polyheterocycle polymers [222]...

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