Aldehydes, reaction

Transition structures for the enol boronoate/aldehyde reaction. 

The Gattermann-Koch formylatioii was found unsuited to the preparation of aldehydes from phenols and phenol ethers such aldehydes may be obtained by Gatteimann s aldehyde reaction. 

This reaction, applicable only to the preparation of hydroxy-aldehydee, is alternative to the Gattermann aldehyde reaction (or the Adams modification of it) given under 4. The yields are usually smaller, but a large quantity of the phenol may be recovered. The following mechanism is consistent with the known facts ... 

By the condensation of a nitrile with a phenol or phenol ether in the presence of zinc chloride and hydrogen chloride a hydroxyaryl- or alkoxyaryl-ketone is produced. The procedure is termed the Hoesch reaction and is clearly an extension of the Gattermann aldehyde reaction (Section IV,121). The reaction gives the best results with polyhydric phenols and their ethers with simple monohydric phenols the imino ester hydrochloride is frequently the sole product for example ... 

Gabriel synthesis Gattermaim aldehyde reaction Gattermann reaction Gattermann-Kocll reaction Gomberg-Hey reaction Grignard reaction... 

A new class of synthetic aldehyde reactions involves effectively reversing the polarity of the carbonyl group by forming a dithiane intermediate. 

The reactions of n- and isobutyialdehyde are chaiactetistic aldehyde reactions of oxidation, reduction, and condensation. Aldehydes (qv) are intermediate in the sequence ... 

Urea—Other Aldehyde Reaction Products. Urea can also react with other aldehydes to form slow release nitrogen fertilizers. However, cost constraints associated with higher aldehydes have either precluded or limited broad commercial development of these products. Two exceptions are isobutyhdene diurea (IBDU), registered trademark of Vigoro Industries, and crotonyHdene diurea (CDU), registered trademark of Chisso-Asahi Fertilizer Co. 

Representative six-membered-ring-forming intramolecular allyIsilane-aldehyde reactions include the following72,73. 

One limitation of these noncatalyzed allyl(trialkyl)- and allyl(triaryl)stannane-aldehyde reactions is the high temperature required unless the aldehyde is activated towards nucleophilic attack. Allyltin halides are much more reactive because of their enhanced Lewis acid character however 2-butenyltin halides show reduced syn I anti selectivity45, and give other products including linear homoallylic alcohols and tetrahydropyrans47. 

The stereoselectivity of the boron trifluoride induced reactions was initially discussed in terms of open-chain, antiperiplanar transition states66. However studies of Lewis acid induced intramolecular allylstannane-aldehyde reactions are supportive of a synclinal process56,67. 

The syn selectivity of boron trifluoride promoted 2-butenylstannane-aldehyde reactions has been examined for a range of different systems less useful syn selectivity was observed for reactions of 2-butenylstannanes with alkyl 2-oxopropanoates68, but better selectivity was found with alkyl 2-oxoacetates69. 

With 2-butenyl- and 3-phenyl-2-propenylstannanes coupling of this Cram selectivity with the intrinsic stereoselectivity of the Lewis acid induced allylstannane-aldehyde reaction gives useful stereocontrol at three contiguous stereogenic centers66,81. 

Ir catalysts supported on binary oxides of Ti/Si and Nb/Si were prepared and essayed for the hydrogenation of a,P-unsaturated aldehydes reactions. The results of characterization revealed that monolayers of Ti/Si and Nb/Si allow a high metal distribution with a small size crystallite of Ir. The activity test indicates that the catalytic activity of these solids is dependent on the dispersion obtained and acidity of the solids. For molecules with a ring plane such as furfural and ciimamaldehyde, the adsorption mode can iirfluence the obtained products. SMSI effect (evidenced for H2 chemisorption) favors the formation of unsaturated alcohol. 

A catalyst used for the u-regioselective hydroformylation of internal olefins has to combine a set of properties, which include high olefin isomerization activity, see reaction b in Scheme 1 outlined for 4-octene. Thus the olefin migratory insertion step into the rhodium hydride bond must be highly reversible, a feature which is undesired in the hydroformylation of 1-alkenes. Additionally, p-hydride elimination should be favoured over migratory insertion of carbon monoxide of the secondary alkyl rhodium, otherwise Ao-aldehydes are formed (reactions a, c). Then, the fast regioselective terminal hydroformylation of the 1-olefin present in a low equilibrium concentration only, will lead to enhanced formation of n-aldehyde (reaction d) as result of a dynamic kinetic control. 

Many years later, Schwartz (Schwartz and Goverde, 1982 Voet and Schwartz, 1983) discovered that the synthesis of adenine via polymerisation of HCN can be accelerated by adding formaldehyde and other aldehydes. Reactions in the gas phase (nitrogen/methane atmosphere) promoted by electrical discharges led to the formation of cyanoacetylene in relatively good yields the latter reacts with urea to give various products, including cytosine (Sanchez et al., 1968). 

Aldehyde-containing macromolecules will react spontaneously with hydrazide compounds to form hydrazone linkages. The hydrazone bond is a form of Schiff base that is more stable than the Schiff base formed from the interaction of an aldehyde and an amine. The hydrazone, however, may be reduced and further stabilized by the same reductants utilized for reductive amination purposes (Chapter 3, Section 4.8). The addition of sodium cyanoborohydride to a hydrazide-aldehyde reaction drives the equilibrium toward formation of a stable covalent complex. Mallia (1992) found that adipic acid dihydrazide derivatization of periodate-oxidized dextran (containing multiple formyl functionalities) proceeds with much greater yield when sodium cyanoborohydride is present. 

The hydrazine-aldehyde reaction has been used intracellularly to deliver non-toxic drug components, which when linked to form a hydrazone bond in situ, become cytotoxic (Rideout, 1986, 1994 Rideout et al., 1990). This same approach has been used to generate enzyme inhibitors in vivo, wherein the hydrazine and aldehyde precursors are not active, but when coupled together within cells to form a hydrazone linkage, become active site binders (Rotenberg etal, 1991). 

In a fume hood, add 10 pi of 5M sodium cyanoborohydride (Sigma) per ml of reaction solution. Caution Cyanoborohydride is extremely toxic. All operations should be done with care in a fume hood. Also, avoid any contact with the reagent, as the 5M solution is prepared in IN NaOH. The addition of a reductant is necessary for stabilization of the Schiff bases formed between an amine-containing protein and the aldehydes on the antibody. For coupling to a hydrazide-activated protein, however, most protocols do not include a reduction step. Even so, hydrazone linkages may be further stabilized by cyanoborohydride reduction. The addition of a reductant during hydrazide/aldehyde reactions also increases the efficiency and yield of the reaction. 

---