Derivatives aldehydes

Reactions with Sahcylaldehydes. Tetraalkyl titanates react in benzene with sahcylaldehyde in a 1 1 or 1 2 molar ratio to give sahcylaldehydotrialkoxy and dialkoxy products, which when heated at reflux seem to undergo a Meewein-Pomidorf reaction to give an aldehyde derived from the alcohol group on the titanate and a reduced titanate complex (37) ... 

From the addition reaetions of acrolein- to aldehyde-derived enamines, aminotetrahydropyrans have been obtained. On heating, these products rearranged to enaminoaldehydes in examples where the initial enamine was disubstituted (320,321). The addition of acrolein to ketone derived enamines has been applied to syntheses of heterocyclic and bridged bieyclic compounds (301,321-323). 

The reactions of dichlorocarbene with morpholine and piperidine enamines derived from cyclopentanone and cyclohexanone have been reported to lead to ring expanded and a-chloromethylene ketone products (355,356). Similarly a-chloro-a, -unsaturated aldehydes were obtained from aldehyde derived enamines (357). Synthesis of aminocyclopropanes (353,359) could be realized by the addition of diphenyldiazomethane (360) and the methylene iodide-zinc reagent to enamines (367). 

While most acylation and benzoylation studies have involved enamines derived from cyclic ketones, extensions to aldehyde derived enamines have also been successful (400). 

The addition of phenylisocyanate to aldehyde-derived enamines resulted in the formation of aminobutyrolactams (438,439). As aminal derivatives these produets can be hydrolyzed to the linear aldehyde amides and thus furnish a route to derivatives of the synthetically valuable malonaldehyde-acid system. With this class of reactions, a second acylation on nitrogen becomes possible and the six-membered cyclization products have been reported (440). Closely related to the reactions of enamines with isocyanates is the condensation of cyclohexanone with urea in base (441). 

Oxidative degradations of aldehyde derived enamines with ozone (4) or sodium dichromate (485-487) have been applied to the formation of progesterone from 3-ketobisnor-4-cholenaldehyde. 

The addition of isocyanides and azide to aldehyde-derived enamines has led to tetrazoles (533,536). On the other hand the vinylogous amide of acetoacetic ester and related compounds reacted with aldehydes, isocyanides and acids to give a-acylaminoamides (534). Iminopyrrolidones and imino-thiopyrrolidones were obtained from the addition of cyclohexylisocyanide and isocyanates or isothiocyanates to enamines (535). An interesting method for the formation of organophosphorus compounds is found in the reactions of imonium salts with dialkylphosphites (536). 

Nal, CeCl3 7H20, CH3CN, rt, 0.5-21 h, 84-96% yield. Chemoselective cleavage of ketone derivatives is observed in the presence of aldehyde derivatives, and enone ketals are cleaved in the presence of simple ketone ketals. 

Citral, or geranaldehyde, and neral or neraldehyde, are, as indicated under geraniol, the two stereoisomeric forms of the aldehydes derived from geraniol and nerol. Citral is best described as a-citr, and neral corresponds with )8-citral. The constitution of the two aldehydes is either that indicated under geraniol, namely,... 

The condensation of 2,5-diunsubstituted pyrroles with formic acid20 is a viable method to produce porphyrins. However, the most common procedure21 22 involves the heating of the corresponding pyrroles 1 with aldehydes and aldehyde derivatives like imines or a Mannich reagent in the presence of acid. The reaction is initiated by electrophilic attack of the aldehyde (or aldehyde derivative) to the pyrrole 1. The formed (hydroxyalkyl)pyrrole 3 then undergoes electrophilic substitution with another pyrrole to form a dipyrrylmethane 4. Repeated addition of aldehyde and pyrrole finally forms a tetrameric (hydroxyalkyl)bilane 5. 

As described in Section 2.3.2, vinylaziridines are versatile intermediates for the stereoselective synthesis of (E)-alkene dipeptide isosteres. One of the simplest methods for the synthesis of alkene isosteres such as 242 and 243 via aziridine derivatives of type 240 and 241 (Scheme 2.59) involves the use of chiral anti- and syn-amino alcohols 238 and 239, synthesizable in turn from various chiral amino aldehydes 237. However, when a chiral N-protected amino aldehyde derived from a natural ot-amino acid is treated with an organometallic reagent such as vinylmag-nesium bromide, a mixture of anti- and syn-amino alcohols 238 and 239 is always obtained. Highly stereoselective syntheses of either anti- or syn-amino alcohols 238 or 239, and hence 2,3-trans- or 2,3-as-3-alkyl-2-vinylaziridines 240 or 241, from readily available amino aldehydes 237 had thus hitherto been difficult. Ibuka and coworkers overcame this difficulty by developing an extremely useful epimerization of vinylaziridines. Palladium(0)-catalyzed reactions of 2,3-trons-2-vinylaziri-dines 240 afforded the thermodynamically more stable 2,3-cis isomers 241 predominantly over 240 (241 240 >94 6) through 7i-allylpalladium intermediates, in accordance with ab initio calculations [29]. This epimerization allowed a highly stereoselective synthesis of (E) -alkene dipeptide isosteres 243 with the desired L,L-... 

Jockers, R., Ziegler, T., and Schmid, R. D. (1995). Interaction between aldehyde derivatives and the aldehyde binding site of bacterial luciferase. ]. Biolumin. Chemilumin. 10 21-27. 

A mixture of lead(iv) acetate (20 mmol) and KOAc (100 mmol) in AcOH (30 ml) was treated with the neat aldehyde-derived silyl enol ether (20mmol) at ambient temperature. After being stirred for 1 h at ambient temperature, the reaction mixture was diluted with water (30ml), and then extracted with pentane (3 x200ml). The combined pentane extracts were washed with saturated sodium hydrogen carbonate solution (2x50ml), dried, concentrated and distilled to give the product a-acetoxyaldehyde (45-78%). 

The mechanism for aldehyde-derived enamines involves a Michael-type 1,4-addition of the enamine to the alkenylcarbene complex to generate a zwit-terionic intermediate which evolves to the final product by cyclisation. On the other hand, ketone-derived enamines react through an initial 1,2-addition to the carbene carbon to generate a different zwitterionic intermediate. Then, a [l,2]-W(CO)5 shift-promoted ring closure produces a new intermediate which, after elimination of the metal moiety, furnishes the corresponding cyclopen-tene derivatives (Scheme 30). 

Quaternary hydrazonium salts (derived from aldehydes) give nitriles when treated with OEt or DBU (p. 488, 1337) as do dimethylhydrazones RCH— NNMe2 when treated with Et2NLi and HMPA. All these are methods of converting aldehyde derivatives to nitriles. For the conversion of aldehydes directly to nitriles, without isolation of intermediates, see 16-21. 

This enolate can then react with a plethora of electrophiles, setting a new stereocenter by a diastereoface-selective reaction. The simplest electrophile to trap enolate 71 is H" ", which can, for example, originate from methanol [89] or diphenyl acetaldehyde (as a readily enolizable aldehyde) [90] leading to the acy-lated catalyst species (Fig. 38). The free catalyst is regenerated by acyl-group transfer to methanol(ate) or the aldehyde-derived enolate, producing methyl or enolesters 72/73 in good yields and enantioselectivities. 

In order to synthesize the DIOP-based ligands, the aldehyde derivatives 3 were treated with commercially available diethyl tartrate in the presence of catalytic amount of PPTS (Scheme 21.2). While good conversions were attained with the naphtyl derivative, they were low with all other aryl compounds and unsuccessful with heteroaromatic moieties (yields < 10%). 

Moreover, an effective extension of the aforementioned procedure is the use of aldehydes derived from carbohydrates to yield polyhydroxylated condensed dihy-dropyrans, as shown by Yadav [383] and Gallos [384]. According to the latter ap-... 

Scheme 2.170. Domino Knoevenagel/hetero-Diels-Alder reaction of aldehydes derived from carbohydrates.

Scheme 4.6 The common core structure of many indole monoterpene alkaloids might be accessed through a tetracyclic Zincke aldehyde-derived building block...

Triisopropylsilyloxyfurans were effective nucleophiles for the vinylogous Mannich addition to iminium ions that were formed by Rh2(cap)4-catalyzed oxidation of N-alkyl groups by THYDRO <06JA5648>. A stereoselective addition of 2-trimethylsilyloxyfurans to aryl aldehydes-derived aldimines employing a chiral phosphine/Ag complex as catalyst was developed <06AG(I)7230>. The prototypical example is shown below. 

A Dotz benzannulation reaction was utilized in the synthesis of the furo[2,3- >]furan core of aflatoxin B2 as illustrated below <06TL2299>. Synthesis of polynuclear aromatic compounds was achieved by using [5+5] cycloaddition of 2-alkynylarylcarbene complexes and enyne-aldehyde derivatives <06TL5303>. 

The thiazolium-catalyzed addition of an aldehyde-derived acyl anion with a Michael acceptor (Stetter reaction) is a well-known synthetic tool leading to the synthesis of highly funtionalized products. Recent developments in this area include the direct nucleophilic addition of acyl anions to nitroalkenes using silyl-protected thiazolium carbinols <06JA4932>. In the presence of a fluoride anion, carbinol 186 is not cleaved to an aldehyde... 

Figure 15.15 An aldehyde derivative of pyrene can be used to couple a hydrophilic amino-PEG-carboxylate spacer by reductive amination. The resultant derivative then can be used to coat a carbon nanotube through pyrene ring adsorption and result in a water-soluble derivative containing terminal carboxylates for coupling amine-containing ligands.

Figure 15.16 Some modification methods that are useful for fullerenes also can be used with carbon nanotubes. The reaction of an N-glycine compound with an aldehyde derivative can result in cycloaddition products, which create pyrrolidine modifications on the nanotube surface.

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