Decarbonylation residue

The residual a-ethoxalyl ester is decarbonylated to cetyl-malonic ester by heating at 160-170° under reduced pressure. A water aspirator is sufficient to facilitate removal of the carbon monoxide formed during the heating. The decarbonylation requires about 1-1,5 hours (Note 7). The cetylmalonic ester which remains as a dark liquid is fractionated under reduced pressure (Note 8). 

If the phenyl glycidic acid esters contain t-butyl- or i-propyl groups on the ester residue decarbonylation and elimination of an olefin occurs in the presence of acidic heterogeneous catalysts at temperatures > 200 °C to form phenylacetalde-hydes with high selectivity (> 80% at 100% conversion) [8]. 

Although not of much real preparative interest, radical decarbonylation has been observed with a large number of aldehydes and ketones at high temperatures and/or under ultraviolet irradiation or in the presence of peroxides. For example, carbon monoxide is eliminated in 90% yield when 3-methyl-3-phenylbutanal is heated for five hours at 130° in the presence of di-tert-butyl peroxide fractionation of the residue then affords 70% of a 1 1 mixture of terr-butyl- and isobutyl-benzene, so that the / ,/ -dimethyl-phenethyl radical formed on elimination of carbon monoxide from the C6H5C(CH3)2CH2CO— radical must be assumed to have partially rearranged.66... 

Furans are volatile, fairly stable compounds with pleasant odours. Furan itself is slightly soluble in water. It is readily available, and its commercial importance is mainly due to its role as the precursor of the very widely used solvent tetrahydrofuran (THF). Furan is produced by the gas-phase decarbonylation of furfural (2-formylfuran, furan-2-carboxaldehyde), which in turn is prepared in very large quantities by the action of acids on vegetable residues mainly from the manufacture of porridge oats and cornflakes. Furfural was first prepared in this way as far back as 1831 and its name is derived from furfur which is the latin word for bran in due course, in 1870, the word furan was coined from the same root. 

It is not clear whether the decarbonylation products J2 35) and 43 which are formed from 30 and 42 both in direct and sensitized irradiation, stem from the triplet state in the sensitized reaction or are the product of residual direct irradiation. 

Comparative in situ XAS of Ru, Pt, and Pd/Al203 catalysts under SCCO2 indicated that rathenium is oxidized during reaction [147], although the resulting RuO, may be less active than the initial metal. The accumulation of carbonaceous residues and slow removal of CO (a by-product of undesired decarbonylation) may play a role in differentiating the activity of Pd versus Pt systems. In situ and ex situ XAS have also... 

Meier et al. [166] applied polarization-modulation infrared reflection absorption spectroscopy (PM-IRAS) to simultaneously monitor hquid phase and adsorbed species during benzyl alcohol selox over Pd(l 11). Anaerobic conditions favored CO surface accumulation via decarbonylation, while surface oxygen fadhtates CO oxidation, leaving no surface residues strongly adsorbed CO and oxygen poison the active surface sites. 

Dibenzyl ketones are suitable guests for this dimeric capsule and they undergo exclusive formation of decarboxylation products in the absence of the hosting dimer, while in the presence of the capsule unusual massive formation of rearrangement products derived by recombination of radical residues and minor amounts of decarbonylation products is observed (Figure 24a). Moreover, as far as the decarbonylation products are concerned, photolysis within the capsule provided only mixed products and no homodimers, confirming that the recombination of radicals occurs in the capsule faster than the in-out exchange. 

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