Ethers heteroaryl

Aryl, heteroaryl, and alkenyl cyanides are prepared by the reaction of halides[656-658] or triflates[659,660] with KCN or LiCN in DMF, HMPA, and THF. Addition of crown ethers[661] and alumina[662] promotes efficient aryl and alkenyl cyanation. lodobenzene is converted into benzonitrile (794) by the reaction of trimethylsiiyl cyanide in EtiN as a solvent. No reaction takes place with aryl bromides and chlorides[663]. The reaction was employed in an estradiol synthesis. The 3-hydroxy group in 796 was derived from the iodide 795 by converting it into a cyano group[664]. 

This scheme eliminates the process of converting bis(etherimide)s to bis(ether anhydride)s. When polyetherimides are fusible the polymerization is performed in the melt, allowing the monamine to distill off. It is advantageous if the amino groups of diamines are more basic or nucleophilic than the by-product monoamine. Bisimides derived from heteroaromatic amines such as 2-arninopyridine are readily exchanged by common aromatic diamines (68,69). High molecular weight polyetherimides have been synthesized from various N,lSf -bis(heteroaryl)bis(etherimide)s. 

In 1959 Carboni and Lindsay first reported the cycloaddition reaction between 1,2,4,5-tetrazines and alkynes or alkenes (59JA4342) and this reaction type has become a useful synthetic approach to pyridazines. In general, the reaction proceeds between 1,2,4,5-tetrazines with strongly electrophilic substituents at positions 3 and 6 (alkoxycarbonyl, carboxamido, trifluoromethyl, aryl, heteroaryl, etc.) and a variety of alkenes and alkynes, enol ethers, ketene acetals, enol esters, enamines (78HC(33)1073) or even with aldehydes and ketones (79JOC629). With alkenes 1,4-dihydropyridazines (172) are first formed, which in most cases are not isolated but are oxidized further to pyridazines (173). These are obtained directly from alkynes which are, however, less reactive in these cycloaddition reactions. In general, the overall reaction which is presented in Scheme 96 is strongly... 

Hie Pd-catalysed coupling of aiyl and heteroaryl halides with 2-hydroxyphenyl 2-propynyl ethers leads to (Z)-2-arylidene-l,4-benzodioxanes <96CC1067>. 

Of all the hydrocarbon-based PEMs, this group most likely has the largest variety of different systems. This is probably due to the wealth of prior knowledge of the nonsulfonated analogues that have been developed over the last several decades as well as the general expectation of higher thermal stability, better mechanical properties, and increased oxidative stability over polystyrene-based systems. Within the context of this section, polyarylenes are systems in which an aryl or heteroaryl ring is part of the main chain of the polymer. This section will, therefore, include polymers such as sulfonated poly (ether ether ketone) and sulfonated poly(imides) but will not include systems such as sulfonated polystyrene, which will be covered in Section 3.3.I.3. 

The indium nonaflate (In(ONf)3)-catalyzed annulation of 2-thienyl- and 2-furylindoles, bithiophenes, and bifurans with methyl propargyl ether also provides tetracyclic heteroaryl annulated [ ]carbazoles in moderate to good yields <2005AGE1336> (Equation (104) Table 10). 

Many 1-heteroaryl-1-alkanols are also easily resolved by hydrolase-catalyzed reactions in organic solvents. Thus, some racemic l-(2-pyridyl)-l-alkanols and isoquinonyl-l-ethanols are easily resolved by CALB (Novozym 435) and vinyl acetate in diisopropyl ether to give the acetates 38—44 (Scheme 4.18) [75]. 

Parlow, J. J. The Use of Anion Exchange Resins for the Synthesis of Combinatorial Libraries Containing Aryl and Heteroaryl Ethers, Tetrahedron Lett. 1996, 37, 5257. 

Figure 6 Chemical structures of diaryl- or aryl-heteroaryl-ethers and thioethers...

Sulfur reagents are strong nucleophiles, and heteroaryl phenyl ethers have been prepared by treating thiophenol with chloro and bromo heterocycles under PT conditions.196,219... 

Potassium hydroxide in DMSO has proved a useful reagent to promote the reaction of activated aryl and heteroaryl chlorides with long chain primary alcohols, to form the corresponding ethers (equation 16).157 The procedure failed with secondary alcohols. 

The use of Candida antarctica lipase B in the kinetic resolution of a series of bicylic 1-heteroaryl primary amines 109 using ethyl acetate as acyl donor in isopropyl ether as organic solvent was studied by Skupinska et al.93 High yields and enantiomeric excess of either enantiomer could be obtained. The undesired enantiomer could be in some cases be recycled by thermal racemization. 

Parlow [25] has demonstrated the use of ammonium exchange resins in the preparation of pooled libraries of aryl and heteroaryl ethers. Two batches of Amberlite IRA-900 were prepared, each of which contained a mixture of 10 aryl or heteroaryl oxides these were then reacted independently with an electrophile to afford a mixture of ethers. 

Parlow JJ, The use of anion exchange resins for the synthesis of combinatorial libraries containing aryl and heteroaryl ethers, Tetrahedron Lett., 37 5257-5260,... 

Activated aryl and heteroaryl halides react with epoxides to yield substituted aromatic ethers (equation 184)1125. 

Imidazole-containing compounds have been utilized as reagents for various synthetic transformations. A convenient access to substituted allyl enol carbonates was established through the reaction of ketone enolates with the complex of allyl l//-imidazole-l-carboxylates 74 and boron trifluoride etherate <07JOC9372>. Relatively mild and highly efficient Cul-catalyzed /V-arylation procedures for imidazoles with aryl and heteroaryl bromides or chlorides have been developed in the presence of ligands 75 and cesium carbonate <07JOC2737>. a, -Unsaturated 2-acyl imidazoles 76 are an alternative and practical class of dienophiles for the DNA-based catalytic asymmetric Diels-Alder reaction in... 

The dihydrotriazoles prepared by cycloaddition of aryl, heteroaryl, and alkyl azides to 3,4-di-azatricyclo[4.2.1.02,5]nona-3,7-diene and 3,4-diazatricyclo[4.2.1.02,5]non-7-ene derivatives were smoothly converted to exo-aziridines by treatment with catalytic amounts of adds (acetic, trifluoroacctic, sulfuric) in aprotic solvents (diethyl ether, dichloromethane, dioxane) at 25-80°C for 4-48 hours, e.g., the sequence 9 -> 10 -> 11 or 12 -> 13 -> 14. The aziridines were further converted to (6-halo and (6-hydroxy aminesl03b. 

---