Aldolcondensation Product

DSM370 has patented platinum systems based upon tetrasulfonated bidentate water soluble ligand 29 (Table 2 x=4, m=0, n=0) as catalysts for the hydroformylation of a mixture 1-butene (45%) and 2-butene (22%) with 33% butane at 100°C and 80 bar CO/H2 in an aqueous/methanol (300/32), CF3SO3H acidic medium. The olefin conversion was 86% and the selectivity to the aldehydes 95% (n/i ratio of 2.8) together with small amounts of aldolcondensation products and acids. The products were isolated from the aqueous catalyst mixture leaving the reaction zone by extraction with ether and the aqueous phase recycled to the reactor. 

Figure 8 outlines possible routes leading to cysteine specific products via 1-deoxypentosone. Under the chosen reaction conditions, (180 °C H-O) norfuraneol is further transformed via 4-hydroxy-5-metnyl-3-(2H)-thiophenone and 2-methyl-3-(2H)-thiophenone, into 2-methyl-3-mercapto-thiophene and 2-methylthiophene, respectively. Norfuraneol is a methylene active compound, which undergoes aldolcondensation with carbonyls forming colored nonvolatile products. 2-Mercaptopropionic acid may be formed from the mercaptoketone by oxidative cleavage. By this route 2-methyl-3-thiolanone and 2-methyl-4,5-dihydro-thiophene may result. 

Butenes are usually derived from Crack-C4 from naphtha steam cracking [27]. After the removal of butadiene (by extraction) and isobutene (by conversion into methyl t-butylether) from the crude stream, the so-called Raffinate II contains 1-butene (50-65%), cis/trons-2-butene, and the isomeric butanes. Raffinate II is the cheapest source of butenes, and their most valuable hydroformylation product is n-pentanal, whereas the isomers 2-methylbutyraldehyde and 3-methylbutyraldehyde are less in demand and lower in value. The main application for -valeraldehyde is its transformation into 2-propylheptanol (2-PH) by aldolcondensation and subsequent hydrogenation of the product (Scheme 14.4) [28, 29]. like 2-EH, 2-PH is also an important plasticizer alcohol. n-Valeraldehyde is also used as an ingredient in flavoring mixtures. w-Valeraldehyde can be converted into -valercarboxylic ester by subsequent oxidation and esterification with tertiary valeric alcohol, providing a useful lubricant and a substitute for Freon. 

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