Hydroxyalkanals, reactions

The direct reaction of 1-alkenes with strong sulfonating agents leads to surface-active anionic mixtures containing both alkenesulfonates and hydroxyalkane sulfonates as major products, together with small amounts of disulfonate components, unreacted material, and miscellaneous minor products (alkanes, branched or internal alkenes, secondary alcohols, sulfonate esters, and sultones). Collectively this final process mixture is called a-olefinsulfonate (AOS). The relative proportions of these components are known to be an important determinant of the physical and chemical properties of the surfactant [2]. 

Another method for the preparation of hydroxyalkanephosphonic acids is the conversion of aldehydes with dialkyl phosphites in the presence of triethylamine or sodium methylate leading directly to the corresponding a-hydroxyalkane-phosphonates. This reaction is reversible, leading to the starting materials aldehyde and diethyl phosphite again [143,146]. 

Since enol carbamates of 4-hydroxyalkanals (or y-hydroxyalkanones) are produced by formation of the C(3)—C(4) bond, we named the process homoaldol reaction 244-246... 

The conversion of co-hydroxyalkanals to the corresponding cyanohydrins in moderate enantioselectivities could also be accomplished by transhydrocyanation with acetone cyanohydrin as the cyanide source. These substrates are considered difficult because of their high solubility in water. Through the employment of an almond meal preparation in a micro-aqueous organic reaction system, the ee-values could be significantly improved [54]. 

The condensation of a,/3-unsaturated carbonyl compounds with phenols has received much attention as a route to chromenes. Problems associated with the instability of alkenals have been largely overcome by the use of masked forms of these reagents. The derived acetals have proved particularly useful in this respect. It is also advantageous to use the acetals of hydroxyalkanals and to introduce the double bond during the course of the reaction. Thus, 4,4-dimethoxy-2-methylbutan-2-ol serves as the equivalent of the unstable 3-methylbut-2-enal. 

Intramolecular olefination of the phosphonates (184) and (186) has been used as the final step in syntheses of (+j-jolkinolides (e.g. 185)108 and the antitumour, antibiotic asperlin (187),109 respectively. In the latter case this confirms the stereochemistry of asperlin as (65,7/ ). A new synthesis of ( )-a,p-unsaturated macrocyclic lactones by intramolecular Wittig reaction of [Pg.356]

The interaction of a dialkyl hydrogenphosphonate with a 3-hydroxyalkanal to afford mixtures of diastereoisomers of the linear dialkyl (l,3-dihydroxyalkyl)phosphonate and derived 1,2-oxaphospholane 2-oxides has already been discussed. Lack of protection at appropriately sited hydroxy groups in carbohydrate molecules allows a similar reaction to occur. With D-erythrose, the 1 1 adduct is obtained as a mixture of epimers 324 (R, R = H, or OH) on acid-catalysed cyclization, these yield the phosphorus epimeric analogues of D-ribo and D-arabino-furanosides with phosphorus in the epimeric position 324 (R = H, R = OH) affords 325 as a mixture of the 2R, 35,4R, 5R and 25, 35,4R, 5R, forms in the ratio 2 1, and 324 (R = OH, R = H) also yields the phosphorus epimeric 321 in the same ratio ... 

It was proposed that this is a general characteristic of all 2-hydroxyalkane-l,l-bisphos-phonic acids. Indeed, a similar result was produced by the product of the reaction of hydroxyacetonitrile with phosphorous acid, l-amino-2-hydroxy-l,l-bisphosphonic acid, which decomposed on acidification to give acetylphosphonic acid, presumably via the corresponding enamine (equation 39f. ... 

The question whether or not radical ions are formed upon irradiation of liquids and stabilized enough for detection or engagement in bimolecular chemical reactions has moved radiation chemists ever since the early days of this research field. This was particularly exciting with respect to low polarity solvents, but even for aqueous solutions conclusions had to rely mainly on indirect evidence. A real breakthrough came with the experimental discovery of the hydrated electron and other powerful one-electron reductants (e.g., a-hydroxyalkane radicals such as (CH3)2C OH). Applying these new tools a large number of organic radical anions were detected and characterized with respect to their optical and chemical properties, particularly by pulse radiolysis. 

In 1999, Schulz reported on the synthesis of (S,S)- or (/ ,/f)-6-hydroxyalkan-4-olides, components of the pheromonal secretion of the butterfly Idea leuconoe. The enantioselective hydrogenation reaction of methyl 4,6-... 

Methyl esters are prepared by reaction with diazomethane, dissolved in petroleum ether and added to the column. Hydrocarbons are eluted with 150-200 mL petroleum ether. Alkenesulfonates are eluted with 500 mL 90 10 petroleum ether/ ethyl ether and hydroxyalkane sulfonate and all disulfonates are eluted with 500 mL ethyl ether. Unesterified material is removed with 50 50 ethyl ether/MeOH. 

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