Alkanes formylation

The combination of alkanes and CO is the simplest of all carbonylation methods which lead to aldehydes. Three research groups have reported the conversion of cyclohexane and carbon monoxide to cyclohexanecarboxaldehyde based on radical carbonylation by photolysis [26]. This alkane-formylation by radical carbo-nylations is conceptually important, but needs further improvement in order to be a useful synthetic method. 

Alkyl-substituted phenols and alkanes were also oxidized to give the corresponding oxygenated products. In the case of isophorene, 3-formyl-5,5-dimethyl-2-cyclohexen-l-one was obtained selectively [110], The regioselectivity of the oxidation was remarkably different from that observed with the corresponding homogeneous analog, which produced 1,4-diketone as a major product [110] ... 

The steps in the hydro formylation reaction are closely related to those that occur in the Fischer-Tropsch process. The Fischer-Tropsch process is the reductive conversion of carbon monoxide to alkanes. It occurs by a repetitive series of carbonylation, migration, and reduction steps which can build up a hydrocarbon chain. 

Good evidence has been obtained that heterogeneous iron, ruthenium, cobalt, and nickel catalysts which convert synthesis gas to methane or higher alkanes (Fischer-Tropsch process) effect the initial dissociation of CO to a catalyst-bound carbide (8-13). The carbide is subsequently reduced by H2to a catalyst-bound methylidene, which under reaction conditions is either polymerized or further hydrogenated 13). This is essentially identical to the hydrocarbon synthesis mechanism advanced by Fischer and Tropsch in 1926 14). For these reactions, formyl intermediates seem all but excluded. 

Neutral formyl complexes which contain ligating CO often decompose by decarbonylation however, several exceptions exist. For instance, the osmium formyl hydride Os(H)(CO)2(PPh3)2(CHO) evolves H2(54). Although the data are preliminary, the cationic iridium formyl hydride 49 [Eq. (14)] may also decompose by H2 evolution (67). These reactions have some precedent in earlier studies by Norton (87), who obtained evidence for rapid alkane elimination from osmium acyl hydride intermediates Os(H)(CO)3(L)(COR) [L = PPh3, P(C2H5)3], Additional neutral formyls which do not give detectable metal hydride decomposition products have been noted (57, 65) however, in certain cases this can be attributed to the instability of the anticipated hydride under the reaction conditions (H2 loss or reaction with halogenated solvents). 

UPAC names pic longest continuous chain including the C of —CH—O and replaces -e of the alkane patne by the suffix -al. The C of CHO is number 1. For compounds with two —CHO groups, the suffix rdial is added tq the alkane name. When other functional groups have naming priority, —CHO is called formyl. 

The importance of a-diazo ketones as synthetic intermediates has led to the development of a number of general methods for their preparation.5 Particularly popular approaches include the acylation of diazo alkanes and the base-catalyzed "diazo group transfer" reaction of sulfonyl azides with 8-dicarbonyl compounds.6-7 While direct diazo transfer to ketone enolates is usually not a feasible process,8-9 diazo transfer to simple ketones can be achieved in two steps by employing an indirect deformylative diazo transfer strategy in which the ketone is first formylated under Claisen condensation conditions, and then treated with a sulfonyl azide reagent such as p-toluenesulfonyl azide.6a,6c,9,i0,11... 

Hydroformylation. Using RhjCOAc) in phosphonium tosylates for hydro-formylation of 1-alkenes at 120°, the catalyst recovery is facilitated. Thus, on cooling of the reaction mixture the rhodium acetate is completely retained in the solid phase and the liquid products are obtained by simple decantation. Variation of substituents at the phosphorus atom of ionic solvents [e.g., (PhjPEt) OTs vs. (BUjPEO OTs ] has remarkable effects on the ratio of alkanals and 2-methylalkanals. 

In general, the yields of aldehydes obtained by Vilsmeier formylation of dithienylmethanes are not good. The same is not true of other bis(2-thienyl)alkanes for example, the compounds 51a-51c gave yields of the 5 -aldehyde of 70,36 87,36 and 82%,39 respectively. The excellent results obtained in these cases suggest that the linking methylene group in dithienyl-... 

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