Aldehydes, tris

Just as electron-donating substituents inhibit hydrate formation, electron-withdrawing ones promote it. Thus K for the hydration of CljCCHO (16) is 2-7 x 104, and this aldehyde (tri-chloroethanal, chloral) does indeed form an isolable, crystalline hydrate (17). The powerfully electron-withdrawing chlorine atoms destabilise the original carbonyl compound, but not the hydrate whose formation is thus promoted ... 

C. SUBSTITUTED ALDEHYDES AND KETONES I. HALOGEN ALDEHYDES Tri-chlor Aldehyde CCI3—CHO Chloral... 

To 2.0 mL of 5% silver nitrate solution, add 1.0 mL of 10% sodium hydroxide in a test tube. To the gray precipitate of silver oxide, AgjO, add 0.5 mL of a 2.8% ammonia solution (10 mL of concentrated ammonium hydroxide diluted to 100 mL). Stopper the tube and shake it. Repeat the process until almost all of the precipitate dissolves (3.0 mL of ammonia at most) then dilute the solution to 10 mL. Empty the test tubes of sodium hydroxide solution, rinse them, and add 1 mL of Tollen s reagent to each. Add one drop (no more) of the substance to be tested by allowing it to run down the inside of the inclined test tube. Set the tubes aside for a few minutes without agitating the contents. If no reaction occurs, warm the mixture briefly on a water bath. As a known aldehyde try one drop of a 0.1 M solution of glucose. A more typical aldehyde to test is benzaldehyde. 

Many other aminoalcohols and related compounds have been recommended as catalysts in enantioselective additions of organozinc reagents to aldehydes. Tri-carbonyl chromium complexation of the aryl ring of 1.14 (R = Me,n-Bu) can lead to improved enantioselectivities [1171], Other arenechromium carbonyl com-plexed aminoalcohols have also been proposed as Zn ligands [1172],... 

Reduction.—/8-(3 -Methyl-2 -butyl)-9-borabicyclo[3,3,l]nonane and the 9-borabicyclo[3,3,l]nonane-pyridine complex are mild chemoselective reducing agents for aldehydes. Tri-n-butyltin hydride on dried silica gel reduces aldehydes rapidly and unhindered ketones relatively slowly yielding the corresponding alcohols in high yields. Sodium borohydride adsorbed on to alumina and the zirconium borohydride (9) reduce aldehydes and ketones to alcohols in aprotic... 

You may wonder why aldehyde A doesn t react, with itself but reacts instead with formaldehyde. This is just one aspect of control in carbonyl condensations, treated thoroughly in frames 217-315 of the Carbonyl Programme. In this case, only aldehyde A can enolise but formaldehyde is more electrophilic. Now try this problem How would you... 

The Dess-Martin periodinane ( DMP ) reagent, U,l-tris(acetyloxy)-l,l-dihydro-l,2-benziodoxol-3(l//)-one, has also been used in several complex syntheses for the oxidation of primary or secondary alcohols to aldehydes or ketones, respectively (e.g., M. Nakatsuka, 1990). It is prepared from 2-iodobenzoic add by oxidation with bromic add and acetylation (D.a Dess, 1983). 

The dipolar ion can react in several ways according to the solvent and the stmcture of the olefin. In inert solvents, if the carbonyl compound is highly reactive (eg, an aldehyde), the dipolar ion can be added to the carbonyl fragment to give the normal ozonide or 1,2,4-trioxolane (7) for example, 1,1-and 1,2-dialkylethylenes react in this manner. Tri- or tetraalkyl-substituted olefins produce a smaH, if any, yield of an ozonide when the ozonolysis is... 

The tris compounds are highly bridged three-dimensional polymers. Photoreduction of aqueous Ti(IV)-containing alcohols or glycols, but not of ethylene glycol, yields Ti(III) and the aldehyde or ketone corresponding to the alcohol (191,192). A possible mechanism is... 

The reaction of ketene itself with tettaalkyl titanates followed by a ketone R R C=0 gives P-hydroxy-esters, R R C0HCH2C02R. Polyinsertion of ketene and aldehyde into the Ti—O bond leads to di-, tri-, and tetraesters, eg, H0CR R CH2C02CR R CH2C02R (200). 

The finished beer (final grain residue alcohol mixture) is ultimately agitated to resuspend its soHds, and transferred to the beer weU storage vessel for holding until it is pumped to the beer stiU. DistiUers try to minimize aeration at this point to avoid formation of excessive aldehydes. 

The alkynylation of estrone methyl ether with the lithium, sodium and potassium derivatives of propargyl alcohol, 3-butyn-l-ol, and propargyl aldehyde diethyl acetal in pyridine and dioxane has been studied by Miller. Every combination of alkali metal and alkyne tried, but one, gives the 17a-alkylated products (65a), (65c) and (65d). The exception is alkynylation with the potassium derivative of propargyl aldehyde diethyl acetal in pyridine at room temperature, which produces a mixture of epimeric 17-(3, 3 -diethoxy-T-propynyl) derivatives. The rate of alkynylation of estrone methyl ether depends on the structure of the alkyne and proceeds in the order propar-gylaldehyde diethyl acetal > 3-butyn-l-ol > propargyl alcohol. The reactivity of the alkali metal salts is in the order potassium > sodium > lithium. 

Both von Hirsch 1U) and Weingarten and White 39) have reported the amination of aldehydes and ketones by tris(dimethylamino)arsine (142) to yield the corresponding gem diamine (143) or enamine (144). Von Hirsch s... 

In 1909, Patemo and Chieffi noted that mixtures of tri- or tetra-substituted olefins and aldehydes formed trimethylene oxides when exposed to sunlight. Biichi later repeated Patemo s experiments by irradiating 2-methyI-2-butene in the presence of benzaldehyde, butyraldehyde, or aeetophenone and rigorously purifying and identifying the resulting products. The reaction thus bears the name of its two primary pioneers and has come to represent any photo-catalyzed [2 + 2] electrocyclization of a carbonyl and an alkene. 

It has been shown that ytterbium tris-(l )-(-)-l,l -binaphthyl-2,2 -diyl phospho-nate can catalyze the reaction of aromatic aldehydes with Danishefsky s diene to... 

Apart from tertiary amines, the reaction may be catalyzed by phosphines, e.g. tri- -butylphosphine or by diethylaluminium iodide." When a chiral catalyst, such as quinuclidin-3-ol 8 is used in enantiomerically enriched form, an asymmetric Baylis-Hillman reaction is possible. In the reaction of ethyl vinyl ketone with an aromatic aldehyde in the presence of one enantiomer of a chiral 3-(hydroxybenzyl)-pyrrolizidine as base, the coupling product has been obtained in enantiomeric excess of up to 70%, e.g. 11 from 9 - -10 ... 

The sainc cheniists have siuee shown that try small amounts of banzaldeliide and mcthyl-salicylio aldehyde are aUo prcseot in the oil-... 

When the aldehyde is heated on the water-bath with 25 per cent, hydrochloric acid, it yields a triphenylmethane derivative, nonamethoxy-triphenylmethane, a body consisting of snow-white crystals, melting at 184 5°. The action of concentrated nitric acid upon the solution in glacial acetic acid of this triphenylmethane derivative gives rise to 1, 2, 5-trimethoxy-4-nitrobenzene (melting at 130°). With bromine, nonamethoxytriphenylmethane combines, with separation of a molecule of trimethoxy bromobenzene, into a tribromo additive compound of hexamethoxy diphenylmethane, a deep violet-blue body. The 1, 2, 5-tri-methoxy-4-bromobenzene (melting at 54 5°) may be obtained more readily from asaronic acid. 

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