Formylation carbonyl compounds

Other carbonyl compounds are within the scope of the reaction ketones give amides, and aldehydes yield nitriles and formyl derivatives of amines ... 

The alkyl derivatives of thiazoles can be catalytically oxidized in the vapor phase at 250 to 400°C to afford the corresponding formyl derivatives (21). Molybdenum oxide, V2O5, and tin vanadate are used as catalysts either alone or with a support. The resulting carbonyl compounds can be selectively oxidized to the acids. 

More recent work has shown that the 2-unsubstituted compound 40 (R = H, R = Pr ) is an effective formyl anion equivalent which reacts at C2 and undergoes both 1,4-addition to a,(3-unsaturated carbonyl compounds and 1,2-addition to aldehydes (93TL3907 96T4719). 

This section deals with investigations specifically aimed at producing homopolymers and copolymers of furan carbonyl compounds by the selective opening of the carbonyl bond. The many reports on polymerization of 2-furaldehyde which in fact deal with complicated acid-catalysed resinification reactions which involve both the formyl group and the furan ring are reviewed in Chapter VI. 

Ab initio molecular orbital calculations are being used to study the reactions of anionic nucleophiles with carbonyl compounds in the gas phase. A rich variety of energy surfaces is found as shown here for reactions of hydroxide ion with methyl formate and formaldehyde, chloride ion with formyl and acetyl chloride, and fluoride ion with formyl fluoride. Extension of these investigations to determine the influence of solvation on the energy profiles is also underway the statistical mechanics approach is outlined and illustrated by results from Monte Carlo simulations for the addition of hydroxide ion to formaldehyde in water. 

Azolides are also capable to acylate anionic metal carbonyl compounds. For instance, disodium tetracarbonylferrate as well as the corresponding ruthenium and osmium compounds can be formylated with formylimidazole in the presence of boric acid methyl ester ... 

Deprotection of 2,2-disubstituted-l,3-dithiolanes to give carbonyl compounds can be achieved using Oxone with KBr in aq. MeCN <06TL8559> and a review of silylated heterocycles as formyl anion equivalents includes reference to 64 <06CC4881>. A method for transformation of propargylic dithiolanes 43 into tetrasubstituted furans has been reported <06SL1209> and Michael addition of enolates to the chiral dithiolane dioxide 65 takes place... 

Abstract Development in the field of transition metal-catalyzed carbonylation of epoxides is reviewed. The reaction is an efficient method to synthesize a wide range of / -hydroxy carbonyl compounds such as small synthetic synthons and polymeric materials. The reaction modes featured in this chapter are ring-expansion carbonylation, alternating copolymerization, formylation, alkoxycarbonylation, and aminocarbonylation. 

The base-catalysed addition of thiols to Jt-electron-deficient alkenes is an important aspect of synthetic organic chemistry. Particular use of Triton-B, in place of inorganic bases, has been made in the reaction of both aryl and alkyl thiols with 1-acyloxy-l-cyanoethene, which behaves as a formyl anion equivalent in the reaction [1], Tetra-n-butylammonium and benzyltriethylammonium fluoride also catalyse the Michael-type addition of thiols to a,P-unsaturated carbonyl compounds [2], The reaction is usually conducted under homogeneous conditions in telrahydrofuran, 1,2-dimethoxyethane, acetone, or acetonitrile, to produce the thioethers in almost quantitative yields (Table 4.22). Use has also been made of polymer-supported qua-... 

Reductive alkylation can also be accomplished by heating carbonyl compounds at 150-250° with 4-5 mol of ammonium formate, formamide, or formates or formamides prepared by heating primary on secondary amines with formic acid at 180-190° (Leuckart reaction) [322]. An excess of85-90% formic acid is frequently used. Formyl derivatives of primary or secondary amines are sometimes obtained as products and have to be hydrolyzed to the corres-... 

The behavior of 2-substituted- or 2-unsubstituted-5(4//)-oxazolones is completely different. Reaction of electrophiles with 2-substimted-5(47/)-oxazolones usually occurs at C-4, whereas reaction of electrophiles with 2-unsubstituted-5(47/)-oxazolones affords the corresponding 5(2//)-oxazolones. The best example of the behavior of 2-unsubstituted-5(47/)-oxazolones involves 4-isopropyl-5(47/)-oxazolone 143, the anion of which can be considered as a formyl anion equiva-lent. ° ° Thus, reaction of 143 with a catalytic amount of triethylamine gives 144 that reacts with a,p-unsaturated carbonyl compounds to afford Michael adducts or with aldehydes to produce the corresponding aldol adducts. Mild acid hydrolysis of 145 yields the corresponding aldehydes (Scheme 7.42). 

Related to this is the use of amino acid derived reagents for resolution of racemic carbonyl compounds and determination of absolute configurations by X-ray analysis at the imine stage. This is exemplified by the L-valinol derived imine of tricarboxyl (l-formyl-2-methoxyphenyl) chromium (see p 417)88. 

Another possibility for creating a new ligand structure is to connect two phos-phaferrocene molecules via their formyl functional groups. The reductive coupling of carbonyl compounds with low-valent Ti reagents - the McMurry reaction - is a technique that has found wide application in organic synthesis [18]. 

The dimerization of a,/3-unsaturated carbonyl compounds is a difficult reaction and where alternative processes are possible these will occur in preference. Thus, a mixture of propenal and 2-methylpropenal yields 2-formyl-5-methyl-3,4-dihydropyran no dimeric products are observed (equation 7). 

Reagents such as LiAlH4 and KH are not effective for the synthesis of formyl complexes. LiAlH4 does react with many metal carbonyl compounds, but it can transfer more than one and usually effects the formation of metal hydride products (50). Similar results are usually found with NaBH4(50), although some neutral formyl complexes (vide infra) can be obtained under special conditions. KH will also react with some metal carbonyls. However, rates are not very rapid, and any formyl intermediates are likely to decompose faster than they form (51). 

The oxidation of a-hydroxy acids by benzyltrimethylammonium tribromide (BTMAB) to the corresponding carbonyl compounds shows a substantial solvent isotope effect, A (H20)/A (D20) = 3.57, but no KIE for a-deuteromandelic acid.133 The oxidation of glucose by hypobromous acid is first order in glucose and the acid.134 [l,l-2H2]Ethanol shows a substantial kinetic isotope effect when oxidized by hexamethylenetetramine-bromine (HABR) in acetic acid to aldehyde.135 Kinetics of the oxidation of aliphatic aldehydes by hexamethylenetetramine-bromine have been studied by the same group.136 Dioxoane dibromide oxidizes y-tocopherol to 5-bromomethyl-y-tocopherylquinone, which spontaneously cyclizes to 5-formyl-y-tocopherol.137... 

Benassi, R., Folli, U., Iarossi, D., Schenetti, L., and Tadei, F., Conformational analysis of organic carbonyl compounds. Part 3. A H and 13C nuclear magnetic resonance study of formyl and acetyl derivatives of benzo[b]thiophen, J. Chem. Soc. Perkin Trans., II, 911, 1983. 

If a stereogenic double bond is established by this Elcb elimination, one usually observes a trans- or an / -sclcctivity. This experimental finding could have two origins (1) product development control (Section 4.1.3), if the stereoselectivity occurs under kinetic control, or (2) thermodynamic control. Thermodynamic control comes into play if the cis, trans- or E,Z-isomeric condensation products can be interconverted via a reversible 1,4-addition of NaOH or KOH. In the trans- or isomer of an ce,/l-un saturated carbonyl compound the formyl or acyl group may lie unimpeded in the plane of the C=C double bond. This geometry allows one to take full advantage of the resonance stabilization C=C—0=0 <-> C—C=C—0 . ... 

On the other hand, in the as- or Z-isomer of an a,/J-unsaturated carbonyl compound the formyl or acyl group interferes to such an extent with the substituent at the other end of the C=C double bond that a planar geometry is no longer possible and the resonance stabilization consequently is reduced. 

In the carbonyl compounds FC(0)Y the C—F bond distances show a strong dependence on the substituent X and shorten from 136.2(2) pm in acetyl fluoride (Y = Me) to 131.6(1) pm carbonyl fluoride (Y = F). In formyl fluoride (Y = H) and carbonyl chloride fluoride (Y = Cl) the C—F bond lengths are intermediate. When CF2 groups are double-bonded to C, O, S or Se, the C—F bond distances are remarkably constant and range only from 131.5 to 131.9 pm. Such bond lengths, however, are shorter by ca 1.5 pm in compounds with C=N double bonds, such as methanimine or 2,3-diaza-l, 3-butadiene. In both compounds only mean values for the C—F bond distances can be derived from the ED experiments. Ab initio calculations for perfluoromethanimine predict that the C—F bond trans to N—F is longer by 0.4 pm than the cis bond. 

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