Alcohols secondary aliphatic

AcCl, NaOH, dioxane, Bu4N HSO, 25°, 30 min, 90% yield. Phase-transfer catalysis with tetra-n-butylammionium hydrogen sulfate effects acylation of sterically hindered phenols and selective acylation of a phenol in the presence of an aliphatic secondary alcohol. 

Interestingly, free nano-iron oxide particles are active catalysts for the selective oxidation of alcohols to yield the corresponding aldehydes/ketones [72, 73]. Different aromatic alcohols and secondary aliphatic alcohols were oxidized with high selectivity, but at low conversion. Here, further improvement should be possible (Scheme 25). 

The application of phase-transfer catalysis to the Williamson synthesis of ethers has been exploited widely and is far superior to any classical method for the synthesis of aliphatic ethers. Probably the first example of the use of a quaternary ammonium salt to promote a nucleophilic substitution reaction is the formation of a benzyl ether using a stoichiometric amount of tetraethylammonium hydroxide [1]. Starks mentions the potential value of the quaternary ammonium catalyst for Williamson synthesis of ethers [2] and its versatility in the synthesis of methyl ethers and other alkyl ethers was soon established [3-5]. The procedure has considerable advantages over the classical Williamson synthesis both in reaction time and yields and is certainly more convenient than the use of diazomethane for the preparation of methyl ethers. Under liquidrliquid two-phase conditions, tertiary and secondary alcohols react less readily than do primary alcohols, and secondary alkyl halides tend to be ineffective. However, reactions which one might expect to be sterically inhibited are successful under phase-transfer catalytic conditions [e.g. 6]. Microwave irradiation and solidrliquid phase-transfer catalytic conditions reduce reaction times considerably [7]. 

In contrast, the results obtained in the methanolysis, acetolysis, and trifluoroacetolysis of the tosylate 91 were not the expected ones. Cram obtained the methyl ether 93, the acetate 94 and the trifluoro-acetate 95 with the same configuration and optical purity as in the direct synthesis from the alcohol 92. These solvolyses at the bridge carbon atom of [2.2]paracyclophane therefore proceed with complete retention of configuration. The rate of acetolysis of the tosylate 91 also deviates considerably from that of aliphatic secondary tosylates it is some 100 times faster than that of 2-butyl tosylate and about the same as that of a-phenylneopentyl tosylate, acetolysis of which is only slightly stereospecific. 

Varieties of primary and secondary alcohols are selectively oxidized to aldehyde or carbonyl compounds in moderate to excellent yields as summarized in Table 3. As can be seen, /(-substituted benzyl alcohols (e.g., -Cl, -CH3, -OCH3, and -NO2) yielded > 90% of product conversion in 3-4 h of reaction time with TOP in the range of 84-155 h (entries 2-5, Table 3), Heterocyclic alcohols with sulfur- and nitrogen-containing compoimds are found to show the best catalytic yield with TOP of 1517 and 902 h for (pyrindin-2-yl)methanol and (thiophene-2-yl) methanol, respectively (entries 9 and 10, Table 3). Some of aliphatic primary alcohols (long chain alcohols) and secondary alcohols (cyclohexanol, its methyl substituted derivatives and norboman-2-ol) are also selectively oxidized by the membrane catalyst (entries 11-14 and 15-17, Table 3) with TOP values in the window of 8-... 

Propanol, 2 Isopropyl Alcohol Isopropanol Secondary Alcohols Secondary Aliphatic Amines... 

R) -specific ADH from L. kefir was used for the reduction of various ketones to the corresponding secondary alcohols. Aliphatic, aromatic, and cyclic ketones as well as keto esters were accepted as substrates. The activities achieved with several substrates were compared with the activity obtained with the standard substrate of ADH, acetophenone (Fig. 2.2.4.4). As the figure shows, recombinant LK-ADH has a very broad substrate spectrum, including many types of ketones. 

In some cases, the effect of reactant structure may outweigh the influence of catalyst nature. This is seen by comparison with the dehydration of aliphatic secondary alcohols and substituted 2-phenylethanols on four different oxide catalysts (Table 4). With aliphatic alcohols, the slope of the Taft correlation depended on the nature of the catalyst (A1203 + NaOH 1.2, Zr02 0.3, Ti02—0.8, Si02—2.8 [55]) whereas for 2-phenyl-ethanols, the slope of the corresponding Hammett correlation had practically the same value (from —2.1 to —2.4) for all catalysts of this series [95]. The resonance stabilisation of an intermediate with a positive charge on Ca clearly predominates over other influences. 

Oxidation of primary and secondary alcohols Aliphatic primary and secondary alcohols are oxidized rapidly and in high yield by 1. Benzylic and primary allylic alcohols are also oxidized in high yield. Benzoin is oxidized slowly (17 hours) and in low yield. 

Interestingly, oxidation of alcohols with active Mn02 can be performed with no solvent.32 Under these conditions, aliphatic secondary alcohols can be oxidized at room temperature and with reasonable yields.33... 

Oxidation of alcohols. 1 Secondary alcohols are oxidized to carbonyl compounds by Clayfen in pentane or hexane under vigorous stirring. Primary benzyl alcohols are oxidized satisfactorily, but primary aliphatic alcohols are oxidized to complex mixtures. Isolated yields are generally>80%. Nitrite esters (RONO) have been identified as intermediates. 

Table 9 Enantioresolution of aliphatic secondary alcohols, CH(OH)(CH3)R, by inclusion method using CAM, LCAM and NDCA.

In order to clarify mechanism of the precise chiral recognition between aliphatic secondary alcohols and 9a or 10a in their inclusion crystal, X-ray structure of a 1 1 inclusion crystal of 9a and (+)-l,3-butanediol (58) was investigated. Finally, it was found that hydrogen bond between the OH group of 9a and that on the chiral carbon of 58 plays an important role to arrange both molecules at close positions to be able to recognize the chirality each other.24... 

Dimethylaminoallene reacts with alcohols, thiols and aliphatic secondary amines to give the adducts CH2=CH(Y)NR2 (Y = OR, SR, NR2) under the influence of acids. The adducts rearrange to the enamines YCH2CH=CHNR2. If Y = SR or NR2, the enamines are obtained in good yields578. 

Capillary gas chromatographic determination of optical purities, investigation of the conversion of potential precursors, and characterization of enzymes catalyzing these reactions were applied to study the biogenesis of chiral volatiles in plants and microorganisms. Major pineapple constituents are present as mixtures of enantiomers. Reductions, chain elongation, and hydration were shown to be involved in the biosynthesis of hydroxy acid esters and lactones. Reduction of methyl ketones and subsequent enantioselective metabolization by Penicillium citrinum were studied as model reactions to rationalize ratios of enantiomers of secondary alcohols in natural systems. The formation of optically pure enantiomers of aliphatic secondary alcohols and hydroxy acid esters using oxidoreductases from baker s yeast was demonstrated. 

Capillary gas chromatographic investigation of diastereoisomeric derivatives revealed that in some fruits, such as passion fruits (9) and blackberries (17), secondary alcohols and their esters are contained in almost optically pure form. On the other hand corn (Zea mays) contains aliphatic secondary alcohols as mixtures of enantiomers the ratios depend upon the chain lengths of the alcohols. Heptan-2-ol is present mainly as (R)-enantiomer with increasing chain length the proportion of (S)-enantiomer increases. A similar distribution has been determined in coconut (Figure 4). 

Quantitative distribution and optical purities of the secondary alcohols obtained after fermentation with Penicillium citrinum are very similar to those isolated from coconut or corn (Figure 4). A combination of stereospecific reduction and following enantioselec-tive metabolization may be one of the keys to explain the ratios of enantiomers of aliphatic secondary alcohols observed in natural systems. 

Kinetic Resolution by Direct Esterification. This is the least common strategy for kinetic resolution and is most commonly executed on racemic alcohols with carboxylic acids in organic solvents. Reports include several alicyclic secondary alcohols such as menthol and various aliphatic secondary alcohols. Kinetic resolution of a variety of racemic saturated, unsaturated, and a-substituted carboxylic acids has also been effected by direct esterification with various alcohols. ... 

Symmetrical and mixed secondary alkylamines with the general formula of R-NH-R and R-NH-R, respectively are used as epoxy hardeners and plant protecting agents. Lower aliphatic secondary amines are frequently prepared by the alkylation of a primary amine or ammonia with an alcohol on a nickel or copper catalyst [1]. In this work highly selective preparation of di-n-propylamine (n-Pr2NH), di-i-butylamine (i-Bu2NH) and N-ethyl-N-n-butylamine (EtNH-nBu) is described. 

This process applies not only to the production of acetone, but more generally to the conversion of aliphatic secondary alcohols to the corresponding ketones. It constitutes a highly flexible technique, making it possible to treat isopropanol and 2-butanol in the same plant, in successive runs. 

Aliphatic secondary diols were also employed as the substrate, but DKRP of these diols did not lead to enantiopure polymers. At most, an ee of 46% was obtained with low molecular weights in the range of 3.3-3.7 kg mol-1. The latter was attributed to the low of selectivity of Novozym 435 for these secondary diols as revealed by kinetic resolution experiments of 2,9-decandiol with vinyl acetate and Novozym 435. Apparently, the S-alcohol showed significant reactivity, decreasing the ee of the polymer. 

Among the non-steroidal alcohols applied to the Oppenauer oxidation are the cis and trans a-decalols (14), which give excellent yields of the corresponding a-decalones (IS).22 Oxidation of phenolic compounds bearing pendent aliphatic secondary alcohols can be readily performed without prior protection of the phenolic alcohol functionality.23 Acid-sensitive acetal 16 is smoothly converted to the corresponding ketone 17, by exploiting a modified experimental procedure.3,24... 

Manganese dioxide oxidizes allylic and benzylic alcohols faster than primary saturated alcohols, but primary and secondary allylic alcohols react at about the same rate. This use of manganese dioxide is particularly important.i Oxidation of benzylic alcohols is also facile and a secondary benzylic alcohol is oxidized faster than a primary saturated alcohol. The secondary benzylic alcohol group in 102 was oxidized to give aryl ketone 103 (94% yield) in preference to reaction at the primary aliphatic hydroxyl. 

Under these solvent-free conditions, oxidation of primary alcohols (e.g. benzyl alcohol) and secondary alcohols (e.g. 1-phenyl-1-propanol) is rather sluggish and poor, and is of little practical utility. Consequently, the process is applicable only to a-hydroxyketones as exemplified by a variety of examples including a mixed benzylic/aliphatic a-hydroxyketone, 2-hydroxypropiophenone, that furnishes the corresponding vicinal diketone [126, 127]. 

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