Tolerance, aliphatic/alcohol

Table II. Aliphatic/Alcohol Tolerance—30 Day Viscosities 20% VYHH Solutions0...

Recently Yamaguchi and Mizuno[ 113] reported ruthenium on alumina to be a powerful and recyclable catalyst for selective alcohol oxidation. This method displayed a large substrate scope (Eq. 29, Table 4) and tolerates the presence of sulfur and nitrogen groups. Only primary aliphatic alcohols required the addition of hydroquinone. TOFs in the range from 4 h 1 (for secondary allylic alcohols) to 18 h 1 (for 2-octanol) were obtained in trifluorotoluene, while in the solvent-free oxidation at 150 °C a TOF of 300 h 1 was observed for 2-octanol. 

The molecular and chemical composition of the polymer will influence its solubility characteristics. Park (A) has discussed the solvent-resin relationships in detail in "Advances in Chemistry Series 12A." They can be summarized as follows Aromatics such as toluene and xylene are primary solvents for only the most soluble of the vinyl resins. The homopolymers have very slight aromatic tolerances. Aliphatic-type solvents are not considered good solvents for vinyls. As with the aromatics, the extremely soluble resins will tolerate aliphatic solvents if a strong ketone is present. Only fair aliphatic tolerance is obtained with the low molecular weight high vinyl chloride content solution polymers. Aliphatic tolerance of the homopolymers is practically nil. The alcohol tolerance of vinyl resins is very limited. Recent studies with the high solubility type metal adhesion copolymers indicate that appreciable quantities of 2-propanol may be used, if a strong ketone solvent is used. 

Two years later, Marko et al. reported an improved catalytic system which only required 0.25 equivalent of potassium carbonate instead of 2 equivalents (89). The oxidation reaction described above is dramatically influenced by the nature of the solvent. Thus, if the reaction was performed in fluorobenzene, total conversion of undecan-2-ol to undecan-2-one could be reached with 0.25 equivalent K2CO3, whereas 2 equivalents of base were necessary in toluene to convert 90% of this secondary aliphatic alcohol (Table VI). These optimized conditions were applied to a variety of functionalized alcohols and the results are reported in Table VII. The catalyst tolerates both sulphur and nitrogen substituents on the substrate. Indeed, (thiophen-2-yl)methanol, N-protected (S)-valinol or (S)-prolinol could be oxidized to the corresponding aldehydes with very good yields. In addition, no racemization was detected for the two P-amino alcohols as well as for (2S,5i )-2-isopropyl-5-methylcyclohexanol. The hindered endo- and exo-borneol are both converted to camphor with similar reaction rates, despite their distinctly different steric properties. 

Even polyalkoxy-s-triazines are quite prone to nucleophilic substitution. For example, 2,4,6-trimethoxy-s-triazine (320) is rapidly hydrolyzed (20°, dilute aqueous alkali) to the anion of 4,6-dimethoxy-s-triazin-2(l )-one (331). This reaction is undoubtedly an /S jvr-4r2 reaction and not an aliphatic dealkylation. The latter type occurs with anilines at much higher temperatures (150-200°) and with chloride ion in the reaction of non-basified alcohols with cyanuric chloride at reflux temperatures. The reported dealkylation with methoxide has been shown to be hydrolysis by traces of water present. Several analogous dealkylations by alkoxide ion, reported without evidence for the formation of the dialkyl ether, are all associated with the high reactivity of the alkoxy compounds which ai e, in fact, hydrolyzed by usually tolerable traces of water. Brown ... 

Alcohol dehydrogenase-catalyzed reduction of ketones is a convenient method for the production of chiral alcohols. HLAD, the most thoroughly studied enzyme, has a broad substrate specificity and accommodates a variety of substrates (Table 11). It efficiently reduces all simple four- to nine-membered cyclic ketones and also symmetrical and racemic cis- and trans-decalindiones (167). Asymmetric reduction of aliphatic acyclic ketones (C-4-C-10) (103,104) can be efficiently achieved by alcohol dehydrogenase isolated from Thermoanaerobium brockii (TBADH) (168). The enzyme is remarkably stable at temperatures up to 85°C and exhibits high tolerance toward organic solvents. Alcohol dehydrogenases from horse liver and T. brockii... 

The Takai-Utimoto reaction of alkyl halides 360 with aldehydes 361 is a convenient method for the synthesis of branched alcohols 363 with high functional group tolerance [455]. Vitamin B12 362 or cobalt phthalocyanine served as the catalyst and CrCl2 as the stoichiometric reducing agent (Fig. 99). The reactions proceeded well with aromatic and aliphatic aldehydes. 

The formation of an aryl-O bond by the reaction of a phenol with air and moisture stable potassium alkenyl and aryltrifluoroborates was mediated by a copper species. The reaction procedure involved catalytic amounts of Cu(OAc)2 with DMAP as a ligand in the presence of oxygen and molecular sieves. A variety of aliphatic primary and secondary alcohols as well as phenols were suitable reaction partners, thus displaying a broad functional group tolerance (Equation (237)).1025... 

An alternative method for the formation of acyl hypoiodites, developed by Barton, involves the treatment of the acid with r-butyl hypoiodite. Subsequent white light photolysis in benzene at room temperature gave good yields of it ides from primary, secondary and tertiary acids (equation 21). The method was not applicable in the presence of alcohols. A more recent technique involving hypervalent iodine is due to Suarez primary, secondary or tertiary aliphatic acids are heated to reflux in tetrachloromediane with iodosylbenzene diacetate and iodine resulting in good yields of iodides. The method is mild and, with obvious exceptions such as unprotected alcohols, is tolerant of many functional groups, as illustrated in equation (22). ... 

The rates of hydride transfer with (123) are only moderate with aldehydes in THF solution. However if no solvent is used and reaction times of several days are tolerated both aliphatic and aryl ketones can be reduced to the corresponding secondary alcohols (equation 53).Although reactions are sluggish,... 

This mechanism (A = acid catalyzed, AC = acyl transfer, 1 = unimolecular) is observed in the esterification of 2,4,6-trisubstituted benzoic acids with R groups of moderate -i-M effect e.g. methyl). The Aac2 mechanism is blocked by the steric interference of the ortho substituents. Therefore, the acylium cation (17) is generated with anhydrous sulfuric acid and then treated with the alcohol (equation 2). R groups with strong -i-M effects, like methoxy, are not tolerable, as the aromatic nucleus undergoes sulfo-nation under the conditions. A variation of the AacI mechanism for aliphatic acids is achieved by using... 

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