1- adamantyl phenyl

To verify such a steric effect a quantitative structure-property relationship study (QSPR) on a series of distinct solute-selector pairs, namely various DNB-amino acid/quinine carbamate CSPpairs with different carbamate residues (Rso) and distinct amino acid residues (Rsa), has been set up [59], To provide a quantitative measure of the effect of the steric bulkiness on the separation factors within this solute-selector series, a-values were correlated by multiple linear and nonlinear regression analysis with the Taft s steric parameter Es that represents a quantitative estimation of the steric bulkiness of a substituent (Note s,sa indicates the independent variable describing the bulkiness of the amino acid residue and i s.so that of the carbamate residue). For example, the steric bulkiness increases in the order methyl < ethyl < n-propyl < n-butyl < i-propyl < cyclohexyl < -butyl < iec.-butyl < t-butyl < 1-adamantyl < phenyl < trityl and simultaneously, the s drops from -1.24 to -6.03. In other words, the smaller the Es, the more bulky is the substituent. The obtained QSPR equation reads as follows ... 

Treatment of hydrazones derived from 1-adamantyl phenyl ketone, pivalophe-none and benzophenone with sulfur monochloride gave pentathianes 232 and hexathianes 233 along with the corresponding ketones and thioketones as the main products (1997H255 Scheme 124). 

The anions PhS-, PhSe" and PhTe" react with 1-adamantyl iodide under similar experimental conditions giving different results122. Thus, 1-adamantyl phenyl sulphide was formed in 45% yield in the reaction with PhS- while with PhSe- and PhTe- ions the products in equation 37 were formed. 

When 1-adamantyl phenyl tellurium was treated with sodium in liquid ammonia, the Te-adamantyl bond is preferentially cleaved, although the Te-phenyl bond is also attacked. The ratio of the fragmentation rates is approximately 132. 

The treatment of hydrazones derived from l-adamantyl(phenyl)ketone, pivalophenone, and benzophenone with S2C12 gave hexathiepanes 131 (Figure 31) along with other products as tetra- and pentathianes (1997H255). 

In Schemes 30 to 35, products of the irradiation of several systems containing carbonyl chromophores (oxoamides, adamantyl phenyl ketones, a-mesitylaceto-phenones, and a-benzonorbomyl aceotophenones) are presented [282,301-303], Primary photoreaction in every one of these cases is intramolecular 7- or 8-hydrogen abstraction. In the majority of these cases the final products of interest are cyclobutanols (Scheme 36). Of the forty compounds examined, the de of the cyclobutanols or cyclopentanols in solution is less than 15%. On the other hand,... 

The addition of (PhSe)2 to the Gif system, mentioned above, leads to trapping of the radical intermediates with the formation of products with C—Se bonds, for example, 12% of 2-adamantyl phenyl selenide is formed from adamantane. 

Tri(l -adamantyl)phenyl, [4] 4J, and octamethyloctahydroanthracen-9-yl, [5] 5Jj, have also been generated from their parent bromides and observed by EPR spectroscopy. Both of these radicals decayed with clean first-order kinetics. 

Figure 28.3 Arrhenius plots of the rate constants for the isomerization of 2,4,6-tri(T-adamantyl) phenyl, 4f, (O) and for the isomerization of octamethyloctahydroanthracen-9-yl, 5f, (x).

Furthermore, the asymmetric catalysis of 27 could accommodate vinylogous aza-enamines as a source of an alkenyl unit, and the use of 27d bearing the 2,6-dimethyl-4-(l-adamantyl)phenyl groups as catalyst led to the establishment of the general and highly enantioselective formal alkenylation of N-benzoyl imines [77]. Since the oxidative transformation of an aza-enamine moiety of the product into a nitrile functionality appeared feasible as described above, this method offered facile access to optically active y-amino a,P-unsaturated nitriles (Scheme 7.50). 

The photodecomposition of 2,1-benzisoxazolium salts gave iV-substituted phenones (Scheme 22). In one case the l-(adamantyl)-3-phenyl-2,l-benzisoxazolium cation (51) did not generate a substituted phenone with reductive ring substitution. Rather, adamantyl ring rupture occurred to produce (52) (Scheme 22) (78JOC123.3, 77JOC3929). 

R = benzyl, ethyl, n-butyl, isoprop adamantyl, t-butyl, phenyl... 

Cp pentamethylcyclopentadienyl Tmp 2,2,6,6-tetramethylpiperidine Dipp 2,6-di(iso-propyl)phenyl Trip 2,4,6-tri(iso-propyl)phenyl Mes 2,4,6-trimethylphenyl Mes 2,4,6-tri(tert-butyl)phenyl Ada adamantyl dmap 4-(dimethylamino)pyridine Tms trimethylsilyl (SiMe3)... 

Alkyldimethylphosphine-boranes 74 underwent enantioselective deprotonation employing (-)-sparteine/s-BuLi, followed by oxidation with molecular oxygen [91, 92] in the presence of triethyl phosphite (Scheme 12) to afford moderate yields of enantiomerically enriched alkyl(hydroxymethyl)methylphosphine-bo-ranes 76, with 91-93% ee in the case of a bulky alkyl group and 75-81% ee in the case of cyclohexyl or phenyl groups [93]. Except for the adamantyl derivative (in which the ee increased to 99%), no major improvement in the ee was observed after recrystallization. 

The FI ligand structure has a significant influence on the ethylene polymerization activity in particular, modification of the R2 substituent has a dramatic effect on the activity (Table 1) [12, 54, 55], Namely, R2 substituents that are sterically smaller than a f-Bu group [i.e., t -Pr (6), Me (7)] significantly reduce the activity (activity < 1 kg mmoF1 Ir1). By contrast, R2 substituents that are sterically larger than the f-Bu group markedly enhance the activity. The activity is thus directly correlated to the steric bulk of the R2 substituent. For example, in the sequence f-Bu (1, 8) < adamantyl (9) < cumyl (10) < 1,1-diphenylethyl (11), the activity increases from 519 (1 R1 = phenyl, R2 = f-Bu) to 2383 kg mmol-1 h-1 (11 R1 = phenyl, R2 = 1,1-diphenylethyl). 

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