Aldehydes from aryl iodides

Almost the same procedure except for using tributyltin hydride as the hydrogen source provides a convenient and versatile method for the synthesis of aldehydes from aryl iodides/bromides, benzylic and vinylic halides, vinylic triflates, and allylic halides. This protocol allows the reactions to proceed at ca. 50° and 1-3 atm of carbon monoxide, and a variety of functional groups can be tolerated (Eqs. 62-64). ... 

Cacchi, S., Fabrizi, G. and Goggiamani, A. (2004) Palladium-catalyzed synthesis of aldehydes from aryl iodides and acetic formic anhydride. Journal of Combinatorial Chemistry, 6, 692-694. 

Synthesis of aryl ketones or aldehydes from aryl tnllates or iodides and organo stannanes in ihe presence of CO and a palladum catalyst... 

The palladium-catalyzed carbonylation of aryl halides in the presence of various nucleophiles is a convenient method for synthesizing various aromatic carbonyl compounds (e.g., acids, esters, amides, thioesters, aldehydes, and ketones). Aromatic acids bearing different aromatic fragments and having various substituents on the benzene ring have been prepared from aryl iodides at room temperature under 1 atm... 

Removal of the iodine atom from aryl iodides proceeds smoothly in a DMF-Bu4NCl04-(Hg) system [561, 562]. A Cd-modified electrode-assisted allylation of aldehydes and ketones has been attained in a DMF-Et4NCl04 system, in which the... 

Yudin and coworkers reported a palladium-catalyzed synthesis of multisubstituted pyridines from amino allenes, aldehydes, and aryl iodides in 2013 [124], Moderate to good yields of the desired pyridines were prepared from readily available building blocks (Scheme 3.62). 

A tandem enolate-arylation-allylic cyclisation, in which an essential z-butyldimethylsilyl ether protecting group delays the cyclisation step until the Pd-catalysed arylation is complete, enables 1-vinyl-l//-[2]benzopyrans 54 to be prepared from 2-bromobenzaldehyde (Scheme 32) <00CC1675>. 4-Substituted isochromans 55 are formed from aldehydes by a Pd-catalysed termolecular queuing cascade. The sequence involves cyclisation of an aryl iodide onto a proximate alkyne followed by an allene insertion. Transmetallation with indium then allows addition to the aldehyde (Scheme 33) . 

Phosphonates have also been prepared from alcohols and (Ar0)2P(=0)Cl, NEts and a TiCl4 catalyst. ° The reaction of (R0)2P(=0)H and aryl iodides with a Cul catalyst leads to aryl phosphonates. " Polymer-bound phosphonate esters have been used for olefination. Dienes are produced when allylic phosphonate esters react with aldehydes. 

Anions (25) derived from aryl and heterocyclic aldehydes have been used by Hunig et al. for the preparation of a large number of ketones in which one residue is aromatic or heterocyclic (equation 9). In view of the competition between displacement and elimination so frequently encountered in reactions of nucleophiles with secondary halides, it is striking that alkylation of (25 R = Ph) proceeds well even with a tertiary iodide. l-Bromo-4-t-butylcyclohexane reacts with (25) to give the trans product (26) with inversion of configuration (equation 10). 

Some color due to small amounts of iodine may be present in substituted styrenes prepared by this procedure from aryl-methylcarbinols synthesized from the corresponding aldehyde and methylmagnesium iodide. If present, iodine may be removed by shaking the crude product with 1 g. of powdered zinc and 25 ml. of water. 

Apart from sodium borohydride, which is frequently used in water or water-alcohol mixtures to reduce ketones or aldehydes selectively, water is rarely used as the solvent in reductions, because of incompatibility with most reducing agents. However, samarium iodide reduction of ketones, as well as alkyl and aryl iodides is accelerated in water [99]. Likewise, the a-deoxygenation of unprotected aldonolac-tones is efficient when the SmI2-tetrahydrofuran-water system is used [100],... 

As outlined in Scheme 6, isovanillin (35) was converted to aryl iodide 36 via MOM-protection, protection of the aldehyde, and subsequent iodination. Hydrolysis of the acetal and Wittig olefination delivered phenol 37 after exposure of the intermediate aldehyde to methanolic hydrochloric acid. Epoxide 41, the coupling partner of phenol 37 in the key Tsuji-Trost-reaction, was synthesized from benzoic acid following a procedure developed by Fukuyama for the synthesis of strychnine [62]. Birch reduction of benzoic acid with subsequent isomerization of one double bond into conjugation was followed by esterification and bromohydrin formation (40). The ester was reduced and the bromohydrin was treated with base to provide the epoxide. Silylation concluded the preparation of epoxide 41, the coupling partner for iodide 37, and both fragments were reacted in the presence of palladium to attain iodide 38. 

Apart from triarylindiums, diarylindium halides and arylindium dihalides, stable in an aqueous media, smoothly react with aryl iodides and bromides at a very low palladium-catalyst loading in a THF / water mixture (8 1 to 6 1, v/v) to give the biaryls in very high yields tolerating free-amino, hydroxy, carboxy groups, as well as aldehyde, nitro group, etc. The presence of a polar cosolvent (water) has been essential... 

A chelation-assisted mthenium-catalyzed arylation of aldehyde 99 was accomplished in combination with a palladium complex [47]. This cooperative catalysis [48] proved applicable to organostannanes and aryl iodides as arylating reagents (Scheme 9.35). The direct arylation proceeded most likely through ruthenium-catalyzed C—H bond activation, subsequent transmetallation to palladium, and reductive elimination from a palladium intermediate. 

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