Aldehydes arylation reaction

Aryl or alkenyl halides attack the central carbon of the allene system in the 2,3-butadien-l-ol 120 to form the 7r-allyl intermediate 121, which undergoes elimination reaction to afford the o,/3-unsaturated ketone 122 or aldehyde. The reaction proceeds smoothly in DMSO using dppe as a ligandflOl]. 

Aromatic Aldehydes. Carbon monoxide reacts with aromatic hydrocarbons or aryl haHdes to yield aromatic aldehydes (see Aldehydes). The reaction of equation 24 proceeds with yields of 89% when carried out at 273 K and 0.4 MPa (4 atm) using a boron trifluoride—hydrogen fluoride catalyst (72), whereas conversion of aryl haHdes to aldehydes in 84% yield by reaction with CO + H2 requires conditions of 423 K and 7 MPa (70 atm) with a homogeneous palladium catalyst (73) and also produces HCl. 

In a synthesis of decinine a phenol was protected as a methanesulfonate that was stable during an Ullman coupling reaction and during condensation, catalyzed by calcium hydroxide, of an amine with an aldehyde. Aryl methanesulfonates are cleaved by warm sodium hydroxide solution. " ... 

Another arylation reaction which uses arenediazonium salts as reagents and is catalyzed by copper should be discussed in this section on Meerwein reactions. It is the Beech reaction (Scheme 10-49) in which ketoximes such as formaldoxime (10.13, R=H), acetaldoxime (10.13, R=CH3), and other ketoximes with aliphatic residues R are arylated (Beech, 1954). The primary products are arylated oximes (10.14) yielding a-arylated aldehydes (10.15, R=H) or ketones (10.15, R=alkyl). Obviously the C=N group of these oximes reacts like a C = C group in classical Meerwein reactions. It is interesting that the addition of some sodium sulfite is necessary for the Beech reaction (0.1 to 0.2 equivalent of CuS04 and 0.03 equivalent of Na2S03). 

The aerobic reduction of aryl and alkyl carboxylates to the corresponding aldehydes. The reaction involves formation of an acyl-AMP intermediate by reaction of the carboxylic acid with ATP NADPH then reduces this to the aldehyde (Li and Rosazza 1998 He et al. 2004). The oxidoreductase from Nocardia sp. is able to accept a range of substituted benzoic acids, naphthoic acids, and a few heterocyclic carboxylic acids (Li and Rosazza 1997). 

Thus, [HRh(C0)(TPPTS)3]/H20/silica (TPPTS = sodium salt of tri(m-sulfophenyl)phopshine) catalyzes the hydroformylation of heavy and functionalized olefins,118-122 the selective hydrogenation of a,/3-unsaturated aldehydes,84 and the asymmetric hydrogenation of 2-(6 -methoxy-2 -naphthyl)acrylic add (a precursor of naproxen).123,124 More recently, this methodology was tested for the palladium-catalyzed Trost Tsuji (allylic substitution) and Heck (olefin arylation) reactions.125-127... 

The palladium-catalyzed cross-coupling reaction featured in this procedure occurs under neutral conditions in the presence of many synthetically useful functional groups (e.g. alcohol, ester, nitro, acetal, ketone, and aldehyde). The reaction works best in N,N-dimethylformamide with bis(triphenylphosphine)palladium(ll) chloride, PdCI2(PPh3)2, as the catalyst. Lithium chloride is added to prevent decomposition of the catalyst.143 13 It is presumed that conversion of the intermediate aryl palladium triflate to an aryl palladium chloride is required for the transmetallation step to proceed.9... 

Since Wakamatsu serendipitously discovered amidocarbonylation while performing the cobalt-catalyzed hydroformyla-tion of olefins in 1971, this unique carbonylation reaction, affording a-amino acids directly from aldehydes, has been extensively studied.More recently, palladium-catalyzed processes have been developed to expand the scope of this reaction.The Pd-catalyzed amidocarbonylation has been applied to aldehydes,aryl halides, and imines. As a related reaction, lactamization " of aryl halides catalyzed by a rhodium complex has also been developed. 

Compared with the analogous hydrogenation of aldehydes, the reaction requires somewhat more drastic conditions (about 200°C and 6 hrs), but the temperature is still within the stability range of the cobalt carbonyl phosphine complexes containing tertiary alkyl phosphines as ligands. If aryl phosphines are used, a more or less pronounced decomposition of the carbonyl complexes can be observed (as indicated by the IR... 

Arenediazonium o-benzenesulfonamide 89 was found to be a new and efficient reagent for the Heck-type arylation reactions of some common substrates containing C-C multiple bonds, i.e., ethyl acrylate, acrylic acid, acroleine, styrene, and cyclopentene <2006T3146>. The reactions are carried out in the presence of Pd(OAc)2 and afford arylated products, for example ethyl cinnamates, cinnamic acids, cinnamic aldehydes, and stilbenes, possessing an ( -configuration, and 1-arylcyclopentenes, in good to excellent yields (Equation 27). 

Aryl ketones or aldehydes.1 Reaction of arylalkanes with DDQ in aqueous acetic acid can result in carbonyl products. Thus reaction of 1 with DDQ in HOAc-H20 results in the ketone 2, believed to be formed by acetylation at the benzylic position followed by acid-catalyzed hydrolysis to the corresponding alcohol, which is oxidized to a ketone by DDQ. 

By far one of the most important reactions through the S l mechanism is formation of a C—C bond by the reaction of aryl halides with carbanions derived from hydrocarbons, ketones, esters, amides, nitriles and even, with some limitations, from aldehydes. The reactions of cyanide ions and carbonyl complexes of Co and Fe also form a new C—C bond. 

The thiazolium-catalyzed addition of an aldehyde-derived acyl anion with a receptor is a valuable synthetic tool leading to the synthesis of highly funtionalized products. Acyl anion receptors include Michael acceptor (Stetter reaction), aromatic aldehyde (benzoin reaction), ketone, nitroalkene, aziridine, activated imine. Recently, nucleophilic addition of acyl anions to unactivated imines has been explored <07CC852>. Treatment of aryl aldehydes with imines 146 in the presence of triazolium salt 147 (20 mol%) and triethylamine (20 mol%) provides the a-amino ketones 148 in good yields. However, this methodology does not work for 4-pyridylaldehyde and tert-buty laldehyde. 

Another commercial aldehyde synthesis is the catalytic dehydrogenation of primary alcohols at high temperature in the presence of a copper or a copper-chromite catalyst. Although there are several other synthetic processes employed, these tend to be smaller scale reactions. For example, acyl halides can be reduced to the aldehyde (Rosemnund reaction) using a palladium-on-barium sulfate catalyst. Formylation of aryl compounds, similar to hydrofomiylation, using HCN and HQ (Gatterman reaction) or carbon monoxide and HQ (Gatterman-Koch reaction) can be used to produce aromatic aldehydes. 

Vinylic ethers (44) can be synthesized in high yields by the cross-coupling of aryl or benzyl halides with tris(2-ethoxyvinyl)borane (4S) in the presence of 1 molej% of a palladium compound such as tetrakis(triphenylphosphine)palladium and a base (Eq. 108) Since vinylic ethers (44) thus obtained can readily be hydrolyzed to aldehydes, this reaction provides a convenient procedure for converting aryl or benzylic halides into the corresponding aldehydes with two more carbon atoms. 

Reaction of the Titanated Bislactim Ether. The titanium derivative of the bislactim ether of cyclo(L-Val-Gly) reacts with alkyl aldehydes, aryl aldehydes, and a,(3-unsaturated aldehydes highly diastereoselectively to give almost exclusively the syn addition products (eq 2). Hydrolysis with dilute Trifluo-roacetic Acid affords (2R, 35 )-(3-hydroxy-a-amino acid methyl esters. a-Amino-y-nitro amino acids can be obtained by 1,4-addition of the titanated bislactim ether to nitroalkenes and subsequent hydrolysis of the adduct. ... 

Historically, the first replacement of a diazonium group by hydrogen was accomplished with alcohols.Of these, ethanol is the best, while methanol tends to convert diazonium compounds to aryl methyl ethers. " The hydrogen atom replacing the diazonium group comes from the alcohol, which is converted to the corresponding aldehyde. The reaction is catalyzed by UV irradiation " and by copper(I) oxide. "" " Copper(I) oxide alone reduces the diazonium compounds, but in poor yields. " The reaction can be carried out in aqueous media " or in organic solvents. ""- " ... 

Acyl azides. A mixture of N.iSi(CH.i).i and CrOi (1 1) in CH2CI3 effects conversion of aldehydes to acyl azides in 70-90% isolated yields. In the case of aryl aldehydes, the reaction is conducted at 25°, but the conversion of aliphatic aldehydes is best conducted at - 10° to prevent rearrangement of the acyl azide to the alkyl isocyanate. 

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