Adamantyl group

M CF3SO3H, PhSCH3 or Tl(OCOCF3)3. The 5-adamantyl group is less prone to sulfoxide formation than is the 5-4-methoxybenzyl group. It is also more stable to CF3COOH. 

Two methods shown below converted 175 to the Z alkene 205 in high yields. No expected E alkene with two bulky 1-adamantyl groups in cis positions was formed because of the quick isomerization at the intermediate stage (98BCJ1181). 

Ru—C(carbene) bond distances are shorter than Ru—P bond lengths, but this can simply be explained by the difference in covalent radii between P and The variation of Ru—C(carbene) bond distances among ruthenium carbene complexes illustrates that nucleophilic carbene ligands are better donors when alkyl, instead of aryl, groups are present, with the exception of 6. This anomaly can be explained on the basis of large steric demands of the adamantyl groups on the imidazole framework which hinder the carbene lone pair overlap with metal orbitals. Comparison of the Ru—C(carbene) bond distances among the aryl-substituted carbenes show... 

A Strecker p T 43 ) synthesis would require aldehyde (6) which can be made from available alcohol (7). We shall now use R for the adamantyl group. 

In another smdy, the introduction of an adamantyl group to the poly(etherimide) structure caused polymer glass transition temperature, Tg, and solubility enhancements in some solvents like chloroform and other aprotic solvents [92]. 

The introduction of bulky side chains that contain adamantyl groups to poly(p-phenylenevinylene) (PPV), a semiconducting conjugated polymer, decreases the number of interchain interactions. This action will reduce the aggregation quenching and polymer photoluminescence properties would be improved [93]. 

Substitution of the bulky adamantyl group on the C(10) position of the bUiverdin pigment structure leads to the distortion of hehcal conformation and hence the pigment color would shift from blue to red [94]. 

In general, an increase in steric demand of the substituents on silicon atoms appears to lead to the formation of more stable disilenes. For example, 3, which has two f-butyl groups, is more stable than 1 while 4, which has two 1-adamantyl groups, is more stable than 3.9 Disilene 4... 

A non-covalently functionalized dendrimer was also applied in a continuous allylic amination reaction.[33] PPI dendrimers functionalized with urea adamantyl groups can act as host molecules for phosphorus ligands equipped with acetyl urea groups (Figure 4.18). The so formed supramolecular complex was reacted with a palladium precursor... 

Steric effects on both the amide and the acyloxyl side chain are similar. Tert-butyl and adamantyl groups on the amide side chain in 29v, 29x, 29c, and 29e (Table 2 entries 53 and 54, 63 and 65) result in lower stretch frequencies that, on average, are only 40 cm-1 higher than their precurser hydroxamic esters. Streck and coworkers have suggested that such changes in dialkyl ketones can be ascribed to destabilisation of resonance form II through steric hindrance to solvation which, in the case of tert-butyl counteracts the inductive stabilisation.127... 

Attachment of the adamantyl group to the ring nitrogen atoms of 3,6-disubstituted [l,2,4]triazolo[5, l-c][l,2,4]tri-azines 51 has been studied by Ulomskii et al. <2002ZOR294> (Scheme 7). These authors found that two products, the A-3-adamantyl 52 and the iV-4-adamantyl compounds 53, can be formed, and the regioselectivity was found to markedly depend on the substituents. Thus, the 2-unsubstituted compound yielded 52 as the only product, whereas 2-methyl and 2-methylsulfano derivatrives afforded 4-adamantyl products 53 in poor to medium yields. 

Lomas and Dubois (113b) also reported that by substitution of 1-adamantyl group(s) for one or two of the ferf-butyl group(s) of di-rm-butyl-o-tolylcarbinol (74), the barrier to rotation was-considerably raised, AG at 200°C being 33.9 and 39.1 kcal/mol, respectively, for the mono-1-adamantyl and di-1-adamantyl compounds in dodecane. Being rigid, the 1-adamantyl group causes more steric interference in the transition state for rotation than does the rm-butyl. 

The first nitrile ylide stable enough to be isolated (i.e., 1) has been prepared by the carbene/nitrile method (1). For this dipole, the anionic component is stabilized by electron delocalization and the nitrilium component by the steric bulk of the adamantyl group to such an effect that it has a melting point of 230 °C. The X-ray structure showed that the nitrile ylide moiety is close to linear and much like the resonance structure shown below. 

Is the stability of 8Ad due to unfavorable kinetics, i.e., the bulky adamantyl groups blocking reaction, or to unfavorable thermochemistry, i.e., loss of aromaticity of the imidazole ring as a result of reaction, or both The distinction is potentially important as understanding could assist in designing stable carbenes. To decide, compare the kinetics and thermodynamics of the insertion of 8Ad into the central CH bond in propane with reactions of 8Me, which should also be aromatic but lacks shielding groups , and 9, which is neither aromatic nor crowded. 

The effect of the size of the acyl group on the barrier for isomer interconversion was examined (82JOC3890) in oxazolidine derivatives 103. The energy barrier, which amounts to 72.8 kJ mor when R = Me, decreases to 53.2 kJ mol when R is an adamantyl group. 

The carbene l,3-di-l-adamantylimidazol-2-ylidene is additionally stabilized by aromaticity of the 5-membered ring and by steric protection by the neighboring adamantyl substituents. Similar carbenes with the adamantyl groups replaced by aryl groups are also stable [162]. An alkyl group may be regarded as a weak X -type substituent. The So state of dime thy lcarbene, (CH3)2C, is predicted to be only 5.9 kJ/mol lower than T by ab initio calculations [163]. 

The fragmentation route of hydroxy-1,4-biradicals could be effectively removed as a viable possibility by replacing the cyclohexyl rings of 82 with a 1-adamantyl group the 1-adamantene which would be formed violates... 

The substitution of a methyl group at carbon 3 of the adamantyl group of 86b (designated 89) lowers the molecular symmetry and makes conceivable the formation of three cis and three trans cyclobutanol photoproducts. Of these, only two cis (90 and 91) and two trans (92 and 93) isomers could be... 

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