Ketones with formic acid, catalysts

This is ordinary electrophilic addition, with rate-determining protonation as the first step.164 Certain other alkynes have also been hydrated to ketones with strong acids in the absence of mercuric salts.165 Simple alkynes can also be converted to ketones by heating with formic acid, without a catalyst.166... 

The same reactions, carried out with potassium carbonate as base in place of a secondary amine, yield exocyclic dienes in good yield, although double-bond isomerization sometimes occurs (equation 38).93 Inclusion of tetra-zi-butylammonium chloride in the reaction mixture stops the double-bond isomerization. Thus, the reaction in equation (38) with the chloride yields only the bis(exomethylene) product in 45% yield in a slow reaction. Some N- and O-heterocyclic products, also, have been prepared by the intramolecular vinyl substitution reaction.94 A 16-membered ring lactone was made by the ring closure of a vinylic iodide group with a vinyl ketone group. The yield, based upon the reactant, was 55% but a stoichiometric amount of bis(acetonitrile)palladium dichloride was employed. The catalyst was prereduced with formic acid so that the reaction proceeded at 25 C (equation 39).95... 

Similarly, 1,5-diketones give pyrans. Conjugated 1,4-diketones, such as 1,4-diphenylbut-2-en-l,4-dione is converted to 2,5-diphenylfuran with formic acid, 5% Pd/C, PEG-200, and a sulfuric acid catalyst with microwave irradiation. Formic acid reacts with alcohols to give orthoformates. Note that alkynyl ketones are converted to furans with palladium (II) acetate. ... 

Heterocyclic Amines. Heterocyclic amines can be alkylated with alkyl halides or with alcohols in the presence of hydrogen plus a nickel catalyst. The Wallach reaction for the alkylation of amines by the action of aldehydes or ketones and formic acid has been studied for piperidine. Reactions between toluene and cyclohexanone with piperidine and formic acid yielded 1-benzyl- and 1-cyclohexylpiperidine, respectively. An optimum amount of formic acid is desired since large amounts are harmful and wasteful. 

Enol formates, which are formylating agents under neutral conditions, are obtained from 1-alkynes and formic acid by arene-ruthenium(II) catalysis Heating acetylenes (phenylacetylene, diphenylacetylene, 1-octyne or 4-octyne) with formic acid to 100°C produces ketones and carbon monoxide. It was shown by NMR spectroscopy that the process involves the intermediate formation of enol formates (equation 35). Treatment of terminal alkynes with carbon dioxide and secondary amines in the presence of a ruthenium catalyst affords vinyl carbamates, e.g. equation 36 d88. reviews, see References 189 and 190. 

Acylation of both aromatic and aliphatic compounds can be carried out with relative ease using acyl halides, acid anhydrides, ketenes, nitriles, amides, acids and esters in the presence of Friedel-Craft catalysts to give ketones. Similar substitution reactions with formic acid derivatives are therefore expected to yield the appropriate aldehydes. However, since the anhydride and acyl halides of formic acid, with the exception of formyl fluoride, are either not known or are not sufficiently stable to be used in Friedel-Crafts type acylation reactions, this objective cannot be fully realized. Table 1.1 compares the main ketone syntheses (based on acylating reagents) with the corresponding aldehyde syntheses (based on formylating reagents). 

A variety of ketones were hydrogenated using Shvo s catalyst at 100 °C using excess formic acid rather than H2 as the source of hydrogen [74], Excellent yields (> 90%) of alcohols were generally obtained in 6 h or less, with total turnovers in the range of 6000-8000. The unsaturated 16-electron Ru complex that results after hydrogen is delivered to the substrate is proposed to react with for-... 

Hydride ion transfer from formic acid and its salts finds widespread application in the reduction of organic substrates, but limited use has been made of the procedure under phase-transfer catalytic conditions. However in the presence of a ruthenium complex catalyst, it is possible to selectively reduce the C=C bonds of conjugated ketones with sodium formate [11], The rate of reduction is fastest with tetrahexyl-ammonium hydrogensulphate and Aliquat the complete reduction of chalcone being effected within one hour, whereas with benzyltriethylammonium chloride only ca. 15% reduction is observed after two hours under similar conditions. 

Treatment of aldehydes or ketones with ammonia, primary or secondary amines in reducing media is called reductive alkylation (of ammonia or amines) or reductive amination (of aldehydes or ketones). Reducing agents are most frequently hydrogen in the presence of catalysts such as platinum, nickel or Raney nickel [955], complex borohydrides [705, 954, 955], formaldehyde or formic acid [522]. 

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