Alkyl- and alkoxy-substitutions

The optical properties can be tuned by variations of the chromophores (e.g. type of side-chains or length of chromophorc). The alkyl- and alkoxy-substituted polymers emit in the bluc-gnecn range of the visible spectrum with high photolu-inincsccncc quantum yields (0.4-0.8 in solution), while yellow or red emission is obtained by a further modification of the chemical structure of the chromophores. For example, cyano substitution on the vinylene moiety yields an orange emitter. 

D.A.M. Egbe, S. Sell, C. Ulbricht, E. Birckner, and U.-W. Grummt, Mixed alkyl- and alkoxy-substituted poly[(phenylene ethynylene)-a/t-(phenylene vinylene)] hybrid polymers synthesis and photophysical properties, Macromol. Chem. Phys., 205 2105-2115, 2004. 

Oxidative coupling was used to form alkyl- and alkoxy-substituted phenanthrenedione products lOOa-d (Table 22) [73]. These compounds can be obtained by other methods, albeit in much lower yields. In this instance, oxidative coupling proceeds even with carbonyl-substituted arenes, and VOF3 gives much better results than thallium- or palladium-mediated coupling procedures. 

The primary adducts (156) and (157) of oxazoles with alkenes and alkynes, respectively, are usually too unstable to be isolated. An exception is compound (158), obtained from 5-ethoxy-4-methyloxazole and 4,7-dihydro-l,3-dioxepin, which has been separated into its endo and exo components. If the dienophile is unsymmetrical the cycloaddition can take place in two senses. This is usually the case in the reactions of oxazoles with monosubstituted alkynes with alkenes on the other hand, regioselectivity is observed. Attempts to rationalize the orientation of the major adducts by the use of various MO indices, such as 7r-electron densities or localization energies and by Frontier MO theory (80KGS1255) have not been uniformly successful. A general rule for the reactions of alkyl- and alkoxy-substituted oxazoles is that in the adducts the more electronegative substituent R4 of the dienophile occupies the position shown in formula (156). The primary adducts undergo a spontaneous decomposition, whose outcome depends on the nature of the groups R and on whether alkenes or alkynes have been employed. 

More recently this procedure has been expanded to include some trisubstituted olefins (Asveld and Kellog, 1980). The wide applicability of these procedures to the preparation of dioxetanes of diverse structure, and what proved to many workers to be a surprising stability of most alkyl- and alkoxy-substituted dioxetanes, have facilitated their study and contributed to the tremendous amount of activity in the field. To date well over 100 dioxetanes have been prepared and scrutinized with the objective of elucidating the mechanistic details of their remarkable transformation to excited state carbonyl-containing products. 

Alkyl- and alkoxy-substituted quinoxalines are readily oxidized using 60-90% hydrogen peroxide in acetic acid. although quinoxaline itself may give rise to quinoxaline-2,3-dione under these conditions.It has been reported that, although uncommon, an explosion hazard exists using this procedure. ... 

In addition to BH3, alkyl- and alkoxy-substituted boranes can also undergo insertion into a B-H bond. The higher stability and commercial availability of these boranes (e.g., BBN, catecholborane) has made them attractive as hydroboration reagents. These substituents can also be utilized to effect stereocenters upon insertion. Since hydroboration proceeds with controlled cis stereochemistry, the use of chiral boron substituents... 

A wide range of alkyl- and alkoxy-substituted PAn s of the general types 6 and 7 have been synthesized by the chemical or electrochemical oxidation of appropriately substituted aniline monomers.133 Such substitution imparts markedly improved solubility in organic solvents to the emeraldine salt products compared to the parent (unsubstituted) PAn/HA salts. The poly(2-methoxyaniline) (POMA) species, in particular, has been the subject of extensive studies.134 137 This species has the additional attractive feature of being soluble in water after being wet with acetone. 

Ogata N, Shibata T. 2000. Binding of alkyl- and alkoxy-substituted simple phenolic compounds to human serum proteins. Res Commun Mol Pathol Pharmacol 107(1-2) 167-173. 

Two types of methathesis polymerization have been used to make PAVs. Thorn-Csanyi and coworkers have used transition-metal-mediated metathesis of divinyl-benzenes to make alkyl- and alkoxy-substituted PPVs, but the products are primarily oligomers [53,54]. 

GRUDZiNSKAs ET AL. Prostaglandin Bronchodilator A. Alkyl and Alkoxy Substitution... 

M.Leclerc and G.Daoust, Structural effect in alkyl and alkoxy-substituted polythiophenes,... 

Other parameters of the palladium(n)-catalysed benzofuran synthesis were explored. Ultimately, it was found that the ideal system employed a 2 1 ligand/palladium ratio (10mol% Pd(OAc)2 and 20mol% ethyl nicotinate) and a substoichiometric amount (20mol%) of NaOAc at 100 °C. With this system in hand, a variety of substituted benzo-furans were accessed (Figure 9.7). The reaction was limited to electron-rich aryl systems the palladation event required a sufficiently nucleophilic arene in order to occur. The aryl subunit, however, tolerated an array of alkyl and alkoxy substitution patterns within the... 

Arylated allenes usually give >95% ( )-allylstannanes, whereas alkyl- and alkoxy-substituted allenes tend to produce predominantly (Z)-isomers (Scheme 30). 

Field-effect transistor Volatile oiganic compounds Alkyl- and alkoxy-substituted regioregular PTh PPy... 

Another route was needed for the preparation of alkyl and alkoxy substituted analogs in die pyrrolo[2,3- ]pyiidine series. An attractive route was utilization of the highly function ized hetero[23- lpyndine intermediate available fiom the Dieckmann condensation of a diester intermediate0. The p> dine tetraesters 12 required by diis route were readily prepared in three steps. Mchael addition of 8 to 9 followed by intramolecular ring closure afforded pyridine 10, which was converted to the 6-chloropyridine 11 by phosphorous oxychloride. Treatment of the 6-chloropyridine triester 11 with sarcosine and sarcosine esters at room temperature afforded a series of 6-aminopyridines 12a-c. 

Across C=S bonds Irradiation of thioxanthenethione 23 in the presence of alkyl- and alkoxy substituted butatrienes (R = H = MeO, t-BuO, PhO, or R = R = Me) gives the [2+2] cycloadducts 24 in over 90 % yields. Apparently, the triplet thione attacks the end of the triene system and the generated diradical cyclizes to give the cycloadducts. 

Mixed alkyl and alkoxy substituted poly(phenylene vinylene) hybrid polymers Characterisation, photoluminescence properties [63]... 

Despite their low molecular weights, these imsubstituted polythiopenes are insoluble in THF and other common organic solvents and are also infusible. Their poor processibility has therefore led to extensive studies of alkyl-and alkoxy- substituted polythiophenes in the hope of enhancing solubility in organic solvents and allowing melt-processing. Synthetic approaches to these substituted polythiophenes are described below. 

Cyclic ethers (Table 8) were studied with LiNlSOgCFglg by Wang et al. [37]. They concluded that THF and THP electrolytes were much more stable than their ahcyl- and alkoxy-derivative electrolytes, since the electron donor performance of alkyl and alkoxy substitutes destroys the stable electron cloud stmctures of five- and six-membered cyclic ethers. This difference in oxidation stability led to good cycling performances of Li/liCoOg coin cells with only LiNlSOgCFalg/THF and THP electrolytes. 

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