Aliphatic aldehydes and

SchifT s reagent A solution of rosaniline in water decolorized with sulphurous acid. Aliphatic aldehydes and aldose sugars give a magenta colour with this reagent with aromatic aldehydes and aliphatic ketones the colour develops more slowly aromatic ketones do not react. 

Reagent A is particularly useful for the treatment of the lower aliphatic aldehydes and ketones which are soluble in water cf. acetaldehyde, p. 342 acetone, p. 346). The Recent is a very dilute solution of the dinitrophenylhydrazine, and therefore is used more to detect the presence of a carbonyl group in a compound than to isolate sufficient of the hydrazone for effective recrystallisation and melting-point determination. 

From nitriles by Stephen s reaction (see under Aliphatic Aldehydes and Section 111,64), for example ... 

A-Substituted pyrroles, furans and dialkylthiophenes undergo photosensitized [2 + 2] cycloaddition reactions with carbonyl compounds to give oxetanes. This is illustrated by the addition of furan and benzophenone to give the oxetane (138). The photochemical reaction of pyrroles with aliphatic aldehydes and ketones results in the regiospecific formation of 3-(l-hydroxyalkyl)pyrroles (e.g. 139). The intermediate oxetane undergoes rearrangement under the reaction conditions (79JOC2949). 

Two substituents on two N atoms increase the number of diaziridine structures as compared with oxaziridines, while some limitations as to the nature of substituents on N and C decrease it. Favored starting materials are formaldehyde, aliphatic aldehydes and ketones, together with ammonia and simple aliphatic amines. Aromatic amines do not react. Suitable aminating agents are chloramine, N-chloroalkylamines, hydroxylamine-O-sulfonic acid and their simple alkyl derivatives, but also oxaziridines unsubstituted at nitrogen. Combination of a carbonyl compound, an amine and an aminating agent leads to the standard procedures of diaziridine synthesis. 

Paal-Knorr synthesis, 4, 118, 329 Pariser-Parr-Pople approach, 4, 157 PE spectroscopy, 4, 24, 188-189 photoaddition reactions with aliphatic aldehydes and ketones, 4, 232 photochemical reactions, 4, 67, 201-205 with aliphatic carbonyl compounds, 4, 268 with dimethyl acetylenedicarboxylate, 4, 268 Piloty synthesis, 4, 345 Piloty-Robinson synthesis, 4, 110-111 polymers, 273-274, 295, 301, 302 applications, 4, 376 polymethylation, 4, 224 N-protected, 4, 238 palladation, 4, 83 protonation, 4, 46, 47, 206 pyridazine synthesis from, 3, 52 pyridine complexes NMR, 4, 165... 

Claisen reaction is the condensation of benzaldehyde with aliphatic aldehydes and ketones containing a-hydrogen C6H5CHO -r CH3CHO C6H5CH=CH CHO -r HjO... 

Several improved methods for the preparation of known unsaturated azlactones as well as some interesting new compounds of this type have been reported. Crawford and Little observed that the direct use of 2-phenyl-5-oxazolone (1) in the Erlenmeyer reaction gave much improved yields (35-74%) of unsaturated azlactones with aliphatic aldehydes and with ketones such as acetone and cyclohexanone [Eq, (1)], The usual procedure of mixing a carbonyl compound, hippuric acid, acetic anhydride, and sodium (or lead) acetate affords poor yields in the aliphatic series. 

The wide range of applicability of the reaction can be seen from Table I. Formaldehyde, aliphatic aldehydes, and aromatic and hetero-... 

A range of electron-withdrawing groups on the nitrogen - N-P(0)Ph2, N-tosyl, and N-SES, for example - were tolerated. Imines derived from aromatic, heteroaromatic, unsaturated, and even aliphatic aldehydes and ketones were employed... 

Aliphatic aldehydes and ketones can be converted to gem-dichlorides by treatment with PCI5. The reaction fails for perhalo ketones. " If the aldehyde or ketone has an a hydrogen, elimination of HCl may follow and a vinylic chloride is a frequent side product ... 

In a related process, a-halo ethers can be prepared by treatment of aldehydes and ketones with an alcohol and HX. The reaction is applicable to aliphatic aldehydes and ketones and to primary and secondary alcohols. The addition of HX to an aldehyde or ketone gives tx-halo alcohols, which are usually unstable, though exceptions are known, especially with perfluoro and perchloro species. °... 

The addition of KCN to triisopropylbenzenesulfonyl hydrazones (53) provides an indirect method for achieving the conversion RR CO RR CHCN. " The reaction is successful for hydrazones of aliphatic aldehydes and ketones. 

Nitrilimines react with hydrazones of aliphatic aldehydes and ketones to yield addition products 9 which cyclise when treated with palladium charcoal at room temperature to give 1,6-dihydro-j-tetrazines 10 <96JCR(S)174>. 

The phenylacetaldehyde reductase involved in the degradation of styrene is also able to accept long-chain aliphatic aldehydes and ketones, and halogenated acetophenones (Itoh et al. 1997). 

An unusual reaction was been observed in the reaction of old yellow enzyme with a,(3-unsat-urated ketones. A dismutation took place under aerobic or anaerobic conditions, with the formation from cyclohex-l-keto-2-ene of the corresponding phenol and cyclohexanone, and an analogous reaction from representative cyclodec-3-keto-4-enes—putatively by hydride-ion transfer (Vaz et al. 1995). Reduction of the double bond in a,p-unsaturated ketones has been observed, and the enone reductases from Saccharomyces cerevisiae have been purified and characterized. They are able to carry out reduction of the C=C bonds in aliphatic aldehydes and ketones, and ring double bonds in cyclohexenones (Wanner and Tressel 1998). Reductions of steroid l,4-diene-3-ones can be mediated by the related old yellow enzyme and pentaerythritol tetranitrate reductase, for example, androsta-A -3,17-dione to androsta-A -3,17-dione (Vaz etal. 1995) and prednisone to pregna-A -17a, 20-diol-3,ll,20-trione (Barna et al. 2001) respectively. 

The general mechanistic features of the aldol addition and condensation reactions of aldehydes and ketones were discussed in Section 7.7 of Part A, where these general mechanisms can be reviewed. That mechanistic discussion pertains to reactions occurring in hydroxylic solvents and under thermodynamic control. These conditions are useful for the preparation of aldehyde dimers (aldols) and certain a,(3-unsaturated aldehydes and ketones. For example, the mixed condensation of aromatic aldehydes with aliphatic aldehydes and ketones is often done under these conditions. The conjugation in the (3-aryl enones provides a driving force for the elimination step. 

Samarium diiodide is another powerful one-electron reducing agent that can effect carbon-carbon bond formation under appropriate conditions.257 Aromatic aldehydes and aliphatic aldehydes and ketones undergo pinacol-type coupling with Sml2 or SmBr2. 

The montmorillonite KlO-catalyzed aza-Diels-Alder reaction of Danishefsky s diene with aldimines, generated in situ from aliphatic aldehydes and p-anisidine, proceeded smoothly in H20 or in aqueous CH3CN to afford 2-substituted 2,3-dihydro-4-pyridones in excellent yields (Eq. 12.47).115 Also, complex [(PPh3)Ag(CBiiH6Br6)] was shown to be an effective and selective catalyst (0.1 mol% loading) for a hetero-Diels-Alder reaction with Danishefsky s diene and the reaction showed a striking dependence on the presence of trace amounts of... 

The reaction can be performed in one flask with great operational ease a mixture of an aldehyde and p-anisidine is stirred in THF for 5-10 h at 50 °C. Then, without removing the water produced, Ni(acac)2, isoprene, and Et2Zn are added in this order at room temperature. The mixture is stirred at the same temperature for the period of time indicated (Table 8). The products 57 and 58 are isolated as a mixture by column chromatograph after the usual work-up. Table 8 demonstrates the scope regarding the kind of aldehyde that encompasses not only aromatic aldehydes but also aliphatic aldehydes and even the parent formaldehyde. Despite the diminished electrophilic reactivity of aldimines, the reaction is complete at room temperature within a reasonable reaction time. The reaction of aldimines proceeds in an opposite sense of stereoselectivity to that of aldehydes and selectively provides 1,3-syn isomers 57. 

Scheme 15 Multigram-scale experiments Et3B-Ni catalysis for aromatic aldehydes and Et2Zn-Ni catalysis for aliphatic aldehydes and their variation (Eq. 15)...

The use of simple aldehydes gives better yields of unsaturated acids this is especially noticeable when aromatic aldehydes are employed.2 Mixtures of afi- and 18,7-unsaturated acids have been reported when aliphatic aldehydes and certain basic catalysts are used.3 4... 

The research has inspired related investigation into the coupling reaction between aromatic aldehydes and benzyl bromide or chloride in water. The yields are slightly higher than the results for allylation despite the fact that aqueous benzylation is intrinsically more difficult than allylation. It is also found that the coupling reaction is chemoselective for aromatic aldehydes over aliphatic aldehydes, and also for aromatic aldehydes over aromatic ketones.98 Aqueous Grignard chemistry is attractive for its use of an environmentally benign solvent, and has been the subject of several... 

The third hypothesis (C) is that reaction takes place through an aldol condensation between the ethyl acetoacetate and the carbonyl form of the sugar. There is some precedent indicating that it is possible for /3-ketonic esters to undergo aldol condensation. These compounds react mole to mole with the aliphatic aldehydes and afford unsaturated substances, which could be formed via an aldol condensation with subsequent dehydration. 

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