Keto aldehydes from

Though the dialdehyde-tropinone synthesis does not succeed when the dialdehyde is replaced by a diketone, Blount and Robinson have shown that 1-methyltropinone (XXXV) can be obtained by the interaction of the keto-aldehyde, laevulinaldehyde. Me. CO. CH. CH. CHO, with methylamine and calcium acetonedicarboxylate, and from this by reduction to 1-methyl- -tropine and benzoylation, 1-methyl tropacocaine (b.p. 210°/15 mm. picrate, m.p. 163-4°) has been prepared. 

Aldehyde (139a) was synthesized independently from (141) by ozonolysis followed by ring closure of the seco-keto-aldehyde (140). 

The most important routes to B-norsteroids involve oxidative fission of 5,6-double bonds to keto acids or keto aldehydes which are then closed to five-membered rings by condensation reactions. Three of the best oxidation methods are exemplified in the following examples chosen from the cholestane, androstane, and pregnane series. 

Petrow described the formation of 3-iminoketones from 3-keto-aldehydes and aniline. Cyclization in the presence of aniline hydrochloride and ZnCh smoothly provides the desired quinoline 26. Bis-imine 24 is the proposed intermediate that undergoes cyclization. The aldimine is more reactive than the ketimine toward cyclization thus, cyclization on the aldimine occurs. When the bis-imine is not formed, partial aniline migration can occur which results in mixtures of cyclized products. 

To synthesize 3-substituted isoxazoles directly, Kochetkov and Khomutova have used the reaction of ethyleneacetals of )S-keto-aldehydes (readily available from jS-chlorovinylketones) with hydroxylamine. Owing to the comparative stability of the dioxolane group, this reaction yields unequivocally the pure 3-substituted isomers (22—>23). The use of noncyclic alkyl )S-ketoacetals in this reaction results in a mixture of 3- and 5-substituted isomers. ... 

Other carbanionic groups, such as acetylide ions, and ions derived from a-methylpyridines have also been used as nucleophiles. A particularly useful nucleophile is the methylsulfinyl carbanion (CH3SOCHJ), the conjugate base of DMSO, since the P-keto sulfoxide produced can easily be reduced to a methyl ketone (p. 549). The methylsulfonyl carbanion (CH3SO2CH2 ), the conjugate base of dimethyl sulfone, behaves similarly, and the product can be similarly reduced. Certain carboxylic esters, acyl halides, and DMF acylate 1,3-dithianes (see 10-10. )2008 Qxj(jatjye hydrolysis with NBS or NCS, a-keto aldehydes or a-... 

The obvious Vfittig disconnection gives stabilised ylid (5fi) and keto-aldehyde (57). We have used many such long-chain dicarbonyl compounds in this Chapter and they are mostly produced from available alkenes by oxidative cleavage (e.g. ozonolysis). In this case, cyclic alkene (58) is the right starting material, and this can be made from alcohol (59) by elimination,... 

The acid (VII) formed in the Jones oxidation is readily separated from the nonacidic organic material by extraction of the ether layer with NaHC03 solution. The material not extracted by NaHC03 (neutral organics) was shown by NMR spectroscopy to consist of primarily the keto aldehyde VI. 

Derivatization of the optically active aldehydes to imines has been used for determination of their enantiomeric excess. Chi et al.3 have examined a series of chiral primary amines as a derivatizing agent in determination of the enantiomeric purity of the a-substituted 8-keto-aldehydes obtained from catalysed Michael additions. The imine proton signals were well resolved even if the reaction was not completed. The best results were obtained when chiral amines with —OMe or —COOMe groups were used [2], The differences in chemical shifts of diastereo-meric imine proton were ca. 0.02-0.08 ppm depending on amine. This method has been also used for identification of isomers of self-aldol condensation of hydrocinnamaldehyde. 

The cycloaddition-isomerization strategy has also been applied to the synthesis of hydrindanone. Thus, by using a modified Kanematsu s procedure, the keto aldehyde 40, a hydrindanone of the steroid C-D ring type, can be synthesized from a substituted furan via a cycloaddition-isomerization procedure and is followed by subsequent transformations . 

Another reagent which has found use in pinacolic coupling is prepared from VC13 and zinc dust.181 182 This reagent is selective for aldehydes that can form chelated intermediates, such as /1-formyl amides, x-amido aldehydes, a-phosphinoyl aldehydes,183 and y-keto aldehydes.184 It can be used for both homodimerization and heterodimerization. In the latter case, the more reactive aldehyde is added to an excess of the second aldehyde. Under these conditions, the ketal formed from the chelated aldehyde reacts with the second aldehyde. 

The well-known Robinson-Schbpf reaction has been applied to the synthesis of JZ-adaline (107) from ketoglutaric acid (457), ammonium chloride, and keto-aldehyde (458) (Scheme 58) 338). The second synthesis of starts with nitrone 459 462). Reaction of 459 with pentylmagnesium bromide gave a hydroxylamine (460) which was oxidized to yield a mixture of nitrones 461 and 462. Without separation of the nitrones (461 and 462), successive treatments with allylmagnesium bromide and then mercuric oxide gave a mixture of desired nitrones 466 and 467 and by-product 468. Nitrones 466 and 467 are capable of 1,3-dipolar cycloaddition and, on heating in chloroform, 466 and 467... 

More recently, the same group achieved a simple, highly stereocontrolled total synthesis of (+)-hirsutic acid (Scheme LXXIX) ". This chirally directed effort developed subsequent to reaction of dl-728 with (+)-di-3-pinanylborane, alkaline hydrogen peroxide oxidation, chromatography, PCC oxidation, and hydrogenolysis. The dextrorotatory hydroxy ketone 729 was nicely crafted into keto aldehyde 730 from which 720 was readily obtained. Once again, the Wacker oxidation played an instrumental role in annulation of the third five-membered ring. The remainder of the asymmetric synthesis was completed as before. 

Typical examples are listed in Table 2.1. A few oxidations are effected by RuO but in general it is too powerful an oxidant for this purpose. The system RuCyaq. NaCl-CCy Pt anode oxidised benzyl alcohol to benzaldehyde and benzoic acid and p-anisaldehyde to p-anisic acid [24], and a wide range of primary alcohols and aldehydes were converted to carboxylic acids, secondary alcohols to ketones, l, -diols to lactones and keto acids from RuOj/aq. NaCl pH 4/Na(H3PO )/Pt electrodes (Tables 2.1-2.4). The system [RuO ] "/aq. K3(S303)/Adogen /CH3Cl3 oxidised benzyhc alcohols to aldehydes [30]. The oxidation catalyst TPAP (( Pr N)[RuO ]) (cf. 1.3.4) is extremely useful as an oxidant of primary alcohols to aldehydes and secondary alcohols to ketones without... 

---