Ketones, with Higher aliphatic

We found also that carbomethoxymethylene triphenylarsorane reacted with a series of aliphatic ketones under very mild conditions (47). For example, with acetone it reacted at room temperature, whereas with higher aliphatic ketones at their refluxing temperature (boiling point of the aliphatic ketones). The yields of the a,/3-unsaturated esters were moderate. 

Aliphatic a-hydroxy ketones are easily reduced by baker s yeast to yield the (7 )-configurated 1,2-diols. The reduction of l-hydroxy-2-propanone to (/ )- ,2-propanediol is still of preparative interest227,232. The corresponding a-hydroxy ketones with higher alkyl chain length are also reduced in high enantioselectivity with moderate to high yield. 

Aliphatic hydrocarbons can be prepared by the reduction of the readily accessible ketones with amalgamated zinc and concentrated hydrochloric acid (Clemmensen method of reduction). This procedure is particularly valuable for the prep>aration of hydrocarbons wdth an odd number of carbon atoms where the Wurtz reaction cannot be applied with the higher hydrocarbons some secondary alcohol is produced, which must be removed by repeated distillation from sodium. 

Subsequently, in 1999 the same group showed that the activity of the ruthenium hydrotalcite was significantly enhanced by the introduction of cobalt(II), in addition to ruthenium(III),in the Brucite layer [115]. For example, cinnamyl alcohol underwent complete conversion in 40 min in toluene at 60 °C, in the presence of ruthenium/cobalt hydrotalcite, compared with 31% conversion under the same conditions with ruthenium hydrotalcite. A secondary aliphatic alcohol, 2-octanol, was smoothly converted into the corresponding ketone but primary aliphatic alcohols, for example, 1-octanol, exhibited extremely low activity. The authors suggested that the introduction of cobalt induced the formation of higher oxidation states of ruthenium, for example, Ru(IV) to Ru( VI), leading to a more active oxidation catalyst. However, on the basis of the reported results it is not possible to rule out low-valent ruthenium species as the active catalyst in a hydridometal pathway. The results obtained in the oxidation of representative alcohols with ruthenium hydrotalcite and ruthe-nium-cobalt-hydrotalcite are compared in Table 5. 

According to these, for purely aliphatic ketones the highest enantioselectivities are achieved for methyl ketones with a second, branched-chained alkyl substituent (84-94% ee). The value of 75 % ee obtained with the straight-chain hexan-2-one is, to the best of our knowledge, in any case better than anything achieved to date with nonenzymatic systems and homogeneous catalysis. Higher selectivities have been reported for reductions with stoichiometric amounts of chiral borohydrides (e.g. 80 % ee for the reduction of octan-2-one) [20]. 

The Wittig-Homer type reaction of aliphatic ketones with dimethyl diazomethylphosphonate gave the diazoalkenes (19), which were trapped by amines thus affording enamines (18) of the next higher aldehydes (Scheme 11). For the preparation of allylic amines, the reader is referred to a comprehensive re-... 

Aliphatic diazo compounds react readily with aldehydes and ketones to produce ketones of higher molecular weight.25 With cyclic ketones the... 

Pentanone is similar to acetone in its behavior, and 1 1 adducts may be obtained from aliphatic aldehydes in good yield (equations 47 and 48). 4-Heptanone and higher symmetrical ketones are much less reactive and give very poor yields of aldols with simple aldehydes. However, the reactions of these ketones with o-phthalaldehyde often provide benzotropone derivatives in excellent yield (e.g. equation 49). Diisopropyl ketone and diisobutyl ketone do not give mixed adducts with aldehydes under tte normal protic conditions. 

Viscous liquid, df 1.09. bp 120-125. bp10 154s mp 14-20. nff 1.462, Vapor press at 25 I x 10-1 mm Hg. Misc with water. Sol in most organic solvents, including ketones, nitriles, esters, aromatic hydrocarbons and alcohols. Practically insol in higher aliphatic hydrocarbons. Hydrolyzed by acids. LDM in male, female rats 91, 42 mg/kg orally ]5, 44 mg/kg dermally, T. B. Gaines, Toxicol Appl Pharmacol 14, 515 (1969). 

The Leuckart-Wallach procedure is not very suitable for use with lower aliphatic ketones. However, acetophenone and similar higher-boiling ketones afford the primary amines in 70-80% yield when treated with the mixture of ammonium formate and formamide (the Ingersoll reagent) that is formed when ammonium formate or an ammonium carbonate-carbamate mixture is heated with formic acid at 165°.1022... 

---