Primary Alcohols to Aldehydes Table

For benzyl and cinnamyl alcohols and for geraniol cf. 2.1.1 above for oxidations of aldehydes see 4.1 and Table 4.1  

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Lalancette et al. described the preparation of chromium(VI) oxide intercalated in graphite and its use as a selective oxidant for primary alcohols to aldehydes (Table 17). Secondary and tertiary alcohols are inert under the reaction conditions, but 1,2-diols are cleaved. However, Ebert and coworkers demonstrated that Lalancette probably used CriOg rather than chromium(VI) oxide intercalated gnq ite for these oxidations. This reagent does appear to show the properties described by Lalancette et al. Indeed, when Kagan and coworkers prepared fully characterize chromium(VI)-inteieiated gnqihite it appeared to lack any oxidative properties. ... 

To the synthetic chemist the most important of the reactions m Table 17 1 are the last two the oxidation of primary alcohols to aldehydes and secondary alcohols to ketones Indeed when combined with reactions that yield alcohols the oxidation methods are so versatile that it will not be necessary to introduce any new methods for preparing aide hydes and ketones in this chapter A few examples will illustrate this point... 

The system (4- Bu-pyH)3[Ru(0)3Cl ]/NM0/PMS/CH2Cl3 catalysed the oxidation of primary alcohols to aldehydes and of secondary alcohols to ketones like TRAP (Tables 2.1 and 2.2), such oxidations did not attack double bonds. As stoich. trans-(PPh )2[Ru(0)2Cl ] -/CH3CN it is a two electron oxidant for alcohols [561]. For tran -[Ru(0)2Cy - in solution the effective oxidant or oxidant precursor is [Ru(0)2Cl3]", and this species is coordinatively unsaturated. That this is the case is suggested by the observation that addition of extra Cl" (as (PPh )Cl) to the green [Ru(0)2Cl3]" in solution (Eq. 1.4) generating the red franx-[Ru(0)3Cl ] ", a markedly less effective catalytic oxidant for alcohols than [Ru(0) Cl ]" [561]. 

The first oxidations of alcohols by stoicheiometric RuO /H O were reported in 1958, of primary alcohols to aldehydes or carboxyhc acids and secondary alcohols to ketones [1]. The first Ru-catalysed oxidation of an alcohol was reported in 1965 when Parikh and Jones used RuO /aq. Na(IO )/CCl (Table 2.3) [2] to oxidise secondary alcohol groups in carbohydrates. 

Table 2.1 Oxidation of primary alcohols to aldehydes and carboxylic acids...

Typical examples are listed in Table 2.1. A few oxidations are effected by RuO but in general it is too powerful an oxidant for this purpose. The system RuCyaq. NaCl-CCy Pt anode oxidised benzyl alcohol to benzaldehyde and benzoic acid and p-anisaldehyde to p-anisic acid [24], and a wide range of primary alcohols and aldehydes were converted to carboxylic acids, secondary alcohols to ketones, l, -diols to lactones and keto acids from RuOj/aq. NaCl pH 4/Na(H3PO )/Pt electrodes (Tables 2.1-2.4). The system [RuO ] "/aq. K3(S303)/Adogen /CH3Cl3 oxidised benzyhc alcohols to aldehydes [30]. The oxidation catalyst TPAP (( Pr N)[RuO ]) (cf. 1.3.4) is extremely useful as an oxidant of primary alcohols to aldehydes and secondary alcohols to ketones without... 

Table 6. Oxidation of unsaturated primary alcohols to aldehydes at the nickel hydroxide electrode...

Table 3. Pemithenate catalysed oxidation of primary alcohols to aldehydes using molecular...

Table 5.1 Oxidation of primary and secondary alcohols to aldehydes and ketones catalyzed by [Cp lrCl2]2 (1) ...

The most profitable is certainly the use of laccase (Lc) with TEMPO. It enables the almost quantitative conversion of primary benzylic and allylic alcohols to aldehydes without overoxidation under mild conditions (Table 14, entries 1 and 2), that is, 25 °C and pH = 4.5 in the presence of atmospheric O2, for a reaction time of 24 h. The successful enzyme is the one obtained from the fungus Trametes villosa. 

Conversion of saturated, primary alkyl and aryl alkyl alcohols into the corresponding aldehydes can be achieved by this method provided that the alcohols are entirely dissolved in the organic phase. Relatively unstable protective groups are not affected, as in the oxidation of the acetonide of 1,2,6-hexanetriol, whereas conjugated and isolated double bonds give rise to side reactions which considerably decrease selectivities and yields.4 Some examples of aldehydes synthesized with this method are reported in Table 1. Under the same conditions, secondary alcohols are oxidized to ketones. Addition of catalytic amounts of quaternary onium salts allows fast and total conversion of primary alcohols and aldehydes into carboxylic acids making this methodology very versatile 4... 

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