Alkoxy-substituted table

The data reported in Table 3 for the 2-butenylborations of 2-(dibenzylamino)propanal shed additional light on this transition state model. The ( )-2-butenylboration of 2-(dibenzyl-amino)propanal evidently proceeds preferentially (90%) by way of transition state 9, suggesting that the bulky dibenzylamino substituent destabilizes transition state 8 (X = NBn2 > CH3). On the other hand, the (Z)-2-butenylboration of 2-(dibenzylamino)propanal is relatively non-selective, compared to the excellent selectivity realized in the (Z)-allylborations of a-chloro- or x-alkoxy-substituted chiral aldehydes. This result suggests that an increase in the steric requirement of X destabilizes transition state 11 such that significantly greater amounts of product are obtained from transition state 10. 

The model process Eq. (15) has been studied by means of the MINDO/3 method to clarify the energetic conditions during the formation of cyclic reactive intermediates in cationic propagation of alkoxy-substituted monomers. The enthalpies of formation in the gas phase AH°g of both the alternative structures e and /were supplemented by the solvation energies Eso]v for transition into solvent CH2C12 with the assistance of the continuum model of Huron and Claverie which leads to heats of formation in solution AH° s. Table 13 contains the calculated results. 

TABLE 2. Hallucinogenic potencies in humans for selected alkoxy-substituted phenylisopropylamines ... 

With regard to the general behavior of oxiranes, studies on kinetic resolution of alkyl or alkoxy substituted linear oxiranes mediated by 0.5 to 0.75 equivalent of HCLA base 53 have shown better enantiomeric discrimination for cis (Table 9, entries 1 and 4) rather than trans or terminal oxiranes (Table 9, entries 2, 3 and 5). 

On heating, 4-(isopropoxy)-2-phenyl-2-(trifluoromethyl)-5(2/i/)-oxazolone 65 underwent decarboxylation to the alkoxy-substituted nitrile ylide 66 that was trapped in a 1,3-dipolar cycloaddition by trifluoroacetophenone to generate 68." Other dipolarophiles reacted similarly. In the absence of a dipolarophile, cyclization of 66 yielded the isoindole 67 (Scheme 7.16 Table 7.11, Fig. 7.12). 

The next development in direct detection of nitrenium ions came from McClelland et al. ° who applied the azide method to LFP measurements. This permitted the direct detection of those arylnitrenium ions implicated in carcinogenic DNA damage. McClelland s approach proved to be particularly useful in the study of 4-aryl and 4-alkoxy substituted phenylnitrenium ions. Apparently, the corresponding singlet nitrenes are sufficiently long lived to allow for protonation in aqueous solution. Several arylnitrenium ions studied by this route are described in Table 13.6. 

Benzhydrylamines are better suited than benzylamines as acid-labile linkers for amines. The MBHA linker ( methylbenzhydrylamine ), which is usually used to prepare peptide amides (see Section 3.3), can also be used as a linker for amines (Entry 1, Table 3.21). Hydrogen fluoride is, however, required as the cleavage reagent. Easier to cleave are alkoxy-substituted benzhydrylamines (Entries 2-5, Table 3.21), which can be prepared from the corresponding benzhydryl chlorides [263] or by reductive alkylation [410] or solvolysis [411] of the Rink amide linker. In the case of benzhydrylamines linked to polystyrene as benzyl ethers, treatment with TFA can lead to the release of the linker into solution (acidolysis of the benzylic C-O bond, see Figure 3.18). 

TABLE 12.4 Voltammetric Oxidation Potentials and Peak Currents (pA/mM) of Alkoxy-Substituted Benzenes, Phenols, and Benzyl Alcohols, and Their Derivatives in MeCN (0.1 M TEAP) at a Glassy-Carbon Electrode... 

Table 12.4 summarizes the voltammetric oxidation potentials and peak currents for l,4-(MeO)2Ph and other alkoxy-substituted benzenes, phenols, and benzyl alcohols. Only the 1,4-(MeO)2PhX members of the series exhibit an initial irreversible anodic cyclic voltammogram via the sequence of Eq. (12.37). These plus the l,2-(MeO)2Ph isomer yield a metastable product from the second oxidation [species A, Eq. (12.37)] that undergoes a reversible reduction. Thus, the two-electron oxidation of dimethoxy benzenes yields the corresponding quinone. 

Further optimization of the P3 substituent revealed that 3,4-bis-alkoxy substitution of the phenyl ring improved potency, with the optimal combination 3-(3-methoxypropoxy) and 4-methoxy (7, Table 2). Compound 7 exhibits exceptional renin inhibitory activity in both buffer and plasma and showed moderate in vivo activity in telemetered, sodium-depleted marmosets, with peak reduction of mean arterial pressure of 9 mm Hg and an 8-h duration of action.20 An X-ray co-crystal structure of compound 7 with recombinant human renin established that the methoxypropoxy sidechain occupies a narrow nonsubstrate pocket, termed S3sp. The importance of terminal methoxy group is... 

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. 

Discotic SCLCPs were synthesized by the group of Grubbs [82]. For this purpose, norbornenes XXVIII-n (n=5, 10) and cyclobutenes XXIX-n (n=5, 10) with alkoxy-substituted triphenylenes as mesogenic units (see Fig. 18) were prepared. Polymerization was carried out with initiator 6. The resulting polymers had a narrow PDI between 1.09 and 1.17. Physico-chemical data for poly-XXVIII and poly-XXIX are listed in Table 18. 

This model also predicts that selectivity for the tranr-fused cycloadducts in nonatriene (n = 0) or deca-triene (n = 1) cyclizations should increase as size of the coefficients at C 2)IC S + n) are increased relative to those at C(l)/C(9 + n), that is, as the polarization of the dienophile or diene is increased. Tables 1 and 2 summarize results of intramolecular Diels-Alder reactions that provide a test of this propo-gai.24.25 it ig tiiat an electron-releasing Et N group at C(9) of the nonatrioioate system leads to a substantial increase in selectivity for the trans-fased product (compare entries 4-6, Table 1). Increased trans stereoselectivity also occurs with C(9)-alkoxy-substituted nonatrienes. A similar effect... 

Table 8 Opioid receptor binding affinities of 14-alkoxy-substituted indolo- and benzofuromorphinans [43, 50, 95]...

Results of reactions of chiral a-methyl aldehydes and several chiral crotyl- and allyl-boron reagents are summarized in Tables 8 and 9. It is apparent from these data that the Brown (Ipc)2B(crotyl) and (Ipc)2B(allyl) reagents (51), (52) and (219) consistently give excellent results for the synthesis of each product diastereomer (Table 8, entries 3-6, 11, 16, 20, and 24 Table 9, entries 1,2, 10 and 18). This is true also for their reactions with chiral a- and 3-alkoxy aldehydes (Scheme 49).i. i4S-i50 Thg tartrate crotylboronates (18) and (19) also display excellent selectivity in the synthesis of crotyl diastereomers (136), (137) and (139) (Table 8, entries 7,10,13,17,25 and 28), but are much less selective for the syndesis of crotyl diastereomer (138), especially from -alkoxy-substituted aldehydes such as (253). Tartrate allylboronate (224) is also less effective than (Ipc)2Ballyl (219) for the synthesis of (257) and (258) in Table 9, and of (266) and (267) in Scheme 49.Substantial improvements in selectivity have been realized by using the taitramide-based allylboronate (228), and the results with this reagent (Table 9, entries 4, 7, 9, 12, 14, 17, 20 and 22) compare very favorably with those obtained with (219). The data... 

The Pd-catalyzed couplings are not only useful for the preparation of fully alkoxy-substituted PPEs 1. Combination of dialkoxy-substituted diiodides with different aromatic diynes leads to other classes of PPEs (Scheme 4). WesH has utilized this strategy to make a PPE, 2d, in which unsubstituted benzene rings alternate with alkoxy-substituted ones (Table... 

Miscellaneous PAEs (Table 14). Several other PAEs have been examined with respect to emission. The most interesting ones are PAEs in which pyridine (7). benzimidazole (8) (Table 14. entries 7—9). or bipyridine (9) (Table 14. entry 1) units are separated by alkoxy-substituted diethynylbenzenes or diethynyl-(3-hexylthiophene)s 15. These polymers display high fluorescence, which can be pH dependent. A decrease in pH leads to a bathochromic shift in the emission of the imidazoles 8 and may thus find use in sensory applications. Bipyridine-containing PPE 9 may be useful to detect and connect polymer chains by metal ions in a supramolecular fashion. However, solid-state emission of these materials is mostly not reported. 

Table 35 Principal synthesis of pyrimidines with (5-alkoxy-substituted enones...

Enaminones 701 demonstrated similar behavior in the reactions with NCN binucleophiles compared with p-alkoxy-substituted enones 700 (Table 36). It should be noted, however, that rather unusual substituents were introduced into the molecules of the target pyrimidines using reagents 701 (Entries 3-9). hi particular, the enaminone fragment of 701 can be a part of aminouracil moiety (Entry 9), although in this case, CCCN-fCN mechanism for the pyrimidine ring formation is possible. 

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