Sodium unsaturated carbonyl compounds

Triethylammonium formate is another reducing agent for q, /3-unsaturated carbonyl compounds. Pd on carbon is better catalyst than Pd-phosphine complex, and citral (49) is reduced to citronellal (50) smoothly[55]. However, the trisubstituted butenolide 60 is reduced to the saturated lactone with potassium formate using Pd(OAc)2. Triethylammonium formate is not effective. Enones are also reduced with potassium formate[56]. Sodium hypophosphite (61) is used for the reduction of double bonds catalyzed by Pd on charcoal[57]. 

Acrolein (H2C=CHCH=0) undergoes conjugate addition with sodium azide in aqueous solution to give N3CH2CH2CH=0 Propanal is not an a 3 unsaturated carbonyl compound and cannot undergo conjugate addition... 

A mixture of 1,4-dioxane and water is often used as the solvent for the conversion of aldehydes and ketones by H2Se03 to a-dicarbonyl compounds in one step (Eq. 8.117).331 Dehydrogenation of carbonyl compounds with selenium dioxide generates the a, (i-unsaturated carbonyl compounds in aqueous acetic acid.332 Using water as the reaction medium, ketones can be transformed into a-iodo ketones upon treatment with sodium iodide, hydrogen peroxide, and an acid.333 Interestingly, a-iodo ketones can be also obtained from secondary alcohol through a metal-free tandem oxidation-iodination approach. 

When the conditions are controlled properly, Zn can mediate the reduction of the C-C double bond of a, (3-unsaturated carbonyl compounds in the presence of a nickel catalyst in aqueous ammonium chloride (Eq. 10.7). The use of ultrasonication enhances the rate of the reaction.15 Sodium hydrogen telluride, (NaTeH), prepared in situ from the reaction of... 

Many examples of the phase-transfer catalysed epoxidation of a,(3-unsaturated carbonyl compounds using sodium hypochlorite have been reported [e.g. 7-10]. The addition of transition metal complexes also aids the reaction [11], but advantages in reaction time or yields are relatively insignificant, whereas the use of hexaethyl-guanidinium chloride, instead of a tetra-alkylammonium salt, enhances the rate of epoxidation while retaining the high yields (>95%) [10]. Intermediate (3-haloalkanols are readily converted into the oxiranes under basic conditions in the presence of benzyltriethylammonium chloride [12]. 

Isoxazoles have been used to transpose functionality within a,/3-unsaturated carbonyl compounds (72JA9128). Thus, on exposing either (E)- or (Z)-/3-ionone oxime (449) to a mixture of iodine-potassium iodide in hot aqueous THF containing sodium bicarbonate, the isoxazole (450) was formed in high yield. Catalytic reduction of this isoxazole led... 

Methylmagnesium N-cyclohexyliso-propylamide, 189 By oxidation at an allylic carbon Selenium dioxide, 272 By reduction of a,0-unsaturated carbonyl compounds Sodium borohydride, 278 Sodium dithionite, 281 Other methods r-Butyllithium, 58 Butyllithium-Potassium f-butoxide,... 

Lithium diisopropylamide, 163 Phenyl azide-Aluminum chloride, 240 Halo carbonyl compounds (see also Unsaturated carbonyl compounds) a-Chloro acids Sodium nitrite, 282 a-Halo aldehydes and ketones... 

Unsaturated carbonyl compounds (see also Acetylenic carbonyl compounds, Allenic carbonyl compounds) Unsaturated acids a,P-Unsaturated acids Sodium chlorite, 280 7,8-Unsaturated acids L-Valinol, 341... 

Varma reported a facile and rapid method for the reduction of aldehydes and ketones to the respective alcohols, using alumina-supported sodium borohydride and microwave irradiation under solvent-free conditions. Aldehydes tend to react at room temperature, while for the reduction of ketones, short microwave irradiation of 30-180 s was applied to produce the corresponding alcohols in 62-92% yield. With unsaturated carbonyl compounds, reduction at the conjugated C=C bond might occur as a side reaction under these conditions (Scheme 4.9)26. 

Asymmetric reduction of a,/ -unsaturated carbonyl compounds using chiral complexes (Section 5.4.1, p. 521) could feasibly lead to optically active allylic alcohols. Other reducing agents which have some merit of regioselectivity, but not stereoselectivity, are sodium cyanoborohydride,244 and sodium boro-hydride in the presence of lanthanide salts.245... 

With sodium borohydride and catalytic amounts of titanyl acetoacetonate, a,fi-unsaturated carbonyl compounds give allyl alcohols regioselectively, whereas a-diketones and acyloins are reduced to vicinal diols.325 Enantioselectivities in the reduction of acetophenone, catalysed by 1,3,2-oxazaborolidones, have been examined using the AM1-SCF MO method. The optimized geometries, thermal enthalpies, and entropies of R and S transition states in the stereo-controlling steps of the reduction have been obtained.326... 

Improvements to the techniques of synthesis of 8-alkyI-/V5-deazapterins have been reported for reactions between 2-amino-6-alkylaminopyrimidin-4(3//)ones and either 1,3-dicarbonyl compounds or 1,2-unsaturated carbonyl compounds which require the use of sodium bisulfite and the control of pH followed by chromatographic purification. The pKa data and protonation sites of the compounds which were prepared were recorded [94JHC1385]. 

Oxaspiropentanes have been obtained from the cyclopropylide 103, prepared by treatment of cyclopropyldiphenylsulfonium tetrafluoroborate 102 either with sodium methylsulfmyl carbanion in dimethoxyethane at —45 °C or with potassium hydroxide in dimethylsulfoxide at 25 °C. While the reaction of the ylide 103 with a,p-unsaturated carbonyl compounds has resulted in selective cyclopropylidene transfer to the a, 3-carbon-carbon double bond leading to spiropentanes, condensation of 103 with non-conjugated aldehydes and ketones led to oxaspiropentanes such as 104, which have been isolated in 59-100% yields, Eq. (30) 57). 

The acetaldehyde reaction works well when one drop of dilute sodium hydroxide is added to acetaldehyde. The acetone reaction is best done with insoluble barium hydroxide, Ba(OH)2- Both approaches keep the base concentration low. Without this precaution, the aldol products are not the compounds isolated from the reaction. With more base, further reactions occur, because the aldol products dehydrate rather easily under the reaction conditions to give stable conjugated unsaturated carbonyl compounds. 

The reaction of keto phosphonates with sodium hydride as base is applicable to the synthrais of a,p-unsaturated carbonyl compounds, even under the conditions of the dOution principle [78]. Thus the keto phosphonate 104 could be transformed by this cyclization reaction into the mixture of the epimers 105 in 28-36% yield. 

Before the introduction of metal-ammonia solutions for the reduction of a,p-unsaturated carbonyl compounds,sodium, sodium amalgam, or zinc in protic media were most commonly employed for this purpose. Some early examples of their use include the conversion of carvone to dihydrocarvone with zinc in acid or alkaline medium, and of cholest-4-en-3-one to cholestanone with sodium in alcohol. These earlier methods are complicated by a variety of side reactions, such as over-reduction, dimerization, skeletal rearrangements, acid- or base-catalyzed isomerizations and aldol condensations, most of which can be significantly minimized by metal-ammonia reduction. 

A lot of progress in this area is due to the work of Trost, who introduced diphenylsulphonium cyclopropylide and phenylthiocyclopropyl lithium as extremely versatile C3-building blocks. The first reagent is easily available from the corresponding sulphonium salt by deprotonation with suitable bases (either under irreversible conditions with dimsyl sodium, or, preferably, in a reversible manner by employing potassium hydroxide in DMSO). The ylide adds to a,) -unsaturated carbonyl compounds forming... 

The addition of hydrazoic acid to quinones follows the general pattern for addition to a,)3-unsaturated carbonyl compounds as previously discussed, with necessary modification to allow for the special interrelationships between quinonoid and benzenoid compounds. The product from reaction of /(-benzoquinone and hydrazoic acid in benzene is 2-azido-l,4-benzohydroquinone, which arises by addition of the reagent followed by enolization ° °. When oxidation of the product is permitted, further addidon to the resulting azidoquinone may occur . Hence, with excess sodium azide in acetic acid, /(-benzoquinone affords 2,5-diazido-l,4-benzohydroquinone (equation 81). 

The C=C double bond of 25 is reduced with sodium hydrogen telluride (NaHTe), which is a mild reagent for chemoselective reduction of a,P-unsaturated carbonyl compounds. This procedure... 

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