1.3- Dialdehydes

Dissolve 7 g. of pure oleic acid in 30 ml. of dry ethyl chloride (chloroform may be used but is less satisfactory), and ozonise at about —30°. Remove the solvent under reduced pressure, dissolve the residue in 50 ml. of dry methyl alcohol and hydrogenate as for adipic dialdehyde in the presence of 0 5 g. of palladium - calcium carbonate. Warm the resulting solution for 30 minutes with a slight excess of semicarbazide acetate and pour into water. Collect the precipitated semicarbazones and dry the... 

If we use the rather unreactive B first we should be able to react one aldehyde at a time. The various dialdehydes are available or can be made by the usual l,n-dicarbonyl routes. Synthesis This is what House did ... 

Cyclopentene-l-carboxaldehydes are obtained from cyclohexene precursors by the sequence cyclohexene - cyclohexane-1,2-diol -> open-chain dialdehyde - cyclopentane aldol. The main advantage of this ring contraction procedure is, that the regio-and stereoselectivity of the Diels-Alder synthesis of cyclohexene derivatives can be transferred to cyclopentane synthesis (G. Stork, 1953 G. BUchi, 1968). 

Analogously, l-brcano-3-oxiininobutan-2-one yields the 4-oximino-ethyl compound (67), while chloromalonic dialdehyde gives rise to the S-formylthiazole (68) (Scheme 31) (618). 

The Stephen s method allows the reduction of nitriles by stannous chloride in acid medium. If the amine chlorhydrate initially formed is hydrolyzed, the corresponding aldehyde is obtained (37, 91). Harington and Moggridge (37) have reduced 4-methyl-5-cyanothiazole by this method (Scheme 23). However, Robba and Le Guen (91) did not obtain the expected products with 4.5-dicyanothiazole and 2-methyl-4,5-dicyanothiazole. These compounds have been reduced with diisobutyl-aluminium hydride with very low yields (3 to 6%) (Scheme 24). In other conditions the reaction gives a thiazole nitrile aldehyde with the same yield as that of the dialdehyde. 

Much of the chemistry of diols—compounds that bear two hydroxyl groups—is analo gous to that of alcohols Diols may be prepared for example from compounds that con tain two carbonyl groups using the same reducing agents employed m the preparation of alcohols The following example shows the conversion of a dialdehyde to a diol by... 

Furan can be catalyticaHy oxidized in the vapor phase with oxygen-containing gases to maleic anhydride (93). Oxidation with bromine or in an electrochemical process using bromide ion gives 2,5-dimethoxy-2,5-dihydrofuran [332-77-4] (19) which is a cycHc acetal of maleic dialdehyde (94—96). 

Novel l,3,4-oxadia2ole-containing polya2omethines have been synthesi2ed by the polycondensation of diamines, 2,5-bis(y -aminophenyl)-l,3,4-oxadia2ole and 2,5-bis(/)-aminophenyl)-l,3,4-oxadia2ole with aromatic dialdehydes, isophthaldehyde, and terephthalaldehyde (example follows), in y -cresol at 20°C (54). 

Alkah manganate(VI) salts are used as oxidants in synthetic organic reactions (100) and their reactions have been observed to be similar to permanganate, except that manganate(VI) exhibits lower reactivity. Additionally, sohd BaVInO in methylene chloride has been reported to achieve high yields for the oxidation of diols to dialdehydes (101). 

Morpholiaoglucopyranosides have beea syathesized from sucrose by selective lead tetraacetate oxidatioa of the fmctofuranosyl ring to a dialdehyde (6). This product was subjected to reductive amination with sodium borohydride and a primary amine such as benzylamine to produce the /V-henzy1morpho1ino derivative (7) (99). 

The dialdehyde also underwent a Fischer cyclization with nitromethane and base to produce a mixture of four diasteriomeric nitropyranosides. The principal product was isolated by chromatography, hydrogenated usiag Raney nickel and then A/-acetylated to give... 

Poly(vinyl alcohol) is readily cross-linked with low molecular weight dialdehydes such as glutaraldehyde or glyoxal (163). Alkanol sulfonic acid and poly(vinyl alcohol) yield a sulfonic acid-modified product (164). 

The Kixnig reaction (Fig. 5) has been used to determine the amount of nicotinic acid and niacinamide. In this procedure, quatemization of the pyridine nucleus by cyanogen bromide is followed by ring opening to generate the putative dialdehyde intermediate. Reaction of this compound with an appropriate base, such as p-rr ethyl am in oph en o1 sulfate (47) or sulfanilic acid (48), generates a dye. The concentration of this dye is deterrnined c olo rime trie ally. 

In the BASF synthesis, a Wittig reaction between two moles of phosphonium salt (vitamin A intermediate (24)) and C q dialdehyde (48) is the important synthetic step (9,28,29). Thermal isomerization affords all /ra/ j -P-carotene (Fig. 11). In an alternative preparation by Roche, vitamin A process streams can be used and in this scheme, retinol is carefully oxidized to retinal, and a second portion is converted to the C2Q phosphonium salt (49). These two halves are united using standard Wittig chemistry (8) (Fig. 12). 

Optical properties of cyanines can be usefiil for both chiral substituents/environments and also third-order nonlinear optical properties in polymer films. Methine-chain substituted die arbo cyanines have been prepared from a chiral dialdehyde (S)-(+)-2-j -butylmalonaldehyde [127473-57-8] (79), where the chiral properties are introduced via the chiral j -butyl group on the central methine carbon of the pentamethine (die arbo cyanine) chromophore. For a nonchiral oxadicarbocyanine, the dimeric aggregate form of the dye shows circular dichroism when trapped in y-cyclodextrin (80). Attempts to prepare polymers with carbocyanine repeat units (linked by flexible chains) gave oligomers with only two or three repeat units (81). However, these materials... 

---