Pentanol, from pentanone

Reduction of 5-chloro-2-pentanone by NADPH in an enzyme-cataly2ed reaction yields (5)-5-chloro-2-pentanol. From which face does the hydrogenation occur ... 

Write the balanced equation for the production of pentanone from pentanol, using dichromate ion as the oxidizing agent. 

In another approach, several ct-hydroxydimethylacetals 258, available according to Scheme la, undergo bimolecular loss of MeOH under acid catalyst, to yield the corresponding 1,4-dioxanes 259 (84JOC4581) (Eq. 42). In the case of 3,3-dimethoxy-2-pentanol (260), which is prepared from 3-pentanone, the cyclization gives dioxane 261 rather than the expected 262 (Scheme 65). The rearrangement of 260 to a mechanistically reasonable precursor of 261 is well known from the work of Creary and Rollin (77JOC4231). 

Taylor and Flood could show that polystyrene-bound phenylselenic acid in the presence of TBHP can catalyze the oxidation of benzylic alcohols to ketones or aldehydes in a biphasic system (polymer-TBHP/alcohol in CCI4) in good yields (69-100%) (Scheme 117) °. No overoxidation of aldehydes to carboxylic acids was observed and unactivated allylic alcohols or aliphatic alcohols were unreactive under these conditions. In 1999, Berkessel and Sklorz presented a manganese-catalyzed method for the oxidation of primary and secondary alcohols to the corresponding carboxylic acids and ketones (Scheme 118). The authors employed the Mn-tmtacn complex (Mn/168a) in the presence of sodium ascorbate as very efficient cocatalyst and 30% H2O2 as oxidant to oxidize 1-butanol to butyric acid and 2-pentanol to 2-pentanone in yields of 90% and 97%, respectively. This catalytic system shows very good catalytic activity, as can be seen from the fact that for the oxidation of 2-pentanol as little as 0.03% of the catalyst is necessary to obtain the ketone in excellent yield. 

Figure 5.16 Enantioselectivity of the redox reaction of ADH from T. ethanolicus with different alcohols (Pham, 1990). Temperature dependence of free energy of activation differences for 2-butanol and 2-pentanol open squares 2-butanol open circles 2-pentanol filled square reduction of 2-butanone filled circle reduction of 2-pentanone.

Figures 12.15-12.18 represent 3-pentanone, hexanoic acid, 1-pentanol, and cyclohexane, respectively. The C=0 stretch typical of ketones is at 1715 cm-1 in the spectrum of 3-pentanone. The hexanoic acid shows a C=0 stretch at 1710 cm"1 and a strong, broad O-H stretch from 2500-3500 cm"1. The O-H stretch typical of alcohols is apparent at 3500 cm-1 in the spectrum of 1-pentanol. The cyclohexane... 

The previous discussion focused on the functional group changes that are possible when hydride reducing agents are used and, when appropriate, their regiochemical preferences. A major aspect of hydride reduction is the stereoehemistry of the reduction, as introduced in Table 4.5. A simple example is 2-pentanone, which is reduced to 2-pentanol. The carbonyl is a prochiral center (sec. 1.4.E) since addition of hydride from the two... 

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