Methyl vinyl ketone, oxidation

Methyl vinyl ketone can be produced by the reactions of acetone and formaldehyde to form 4-hydroxy-2-butanone, followed by dehydration to the product (267,268). Methyl vinyl ketone can also be produced by the Mannich reaction of acetone, formaldehyde, and diethylamine (269). Preparation via the oxidation of saturated alcohols or ketones such as 2-butanol and methyl ethyl ketone is also known (270), and older patents report the synthesis of methyl vinyl ketone by the hydration of vinylacetylene (271,272). 

Dichloroethylphosphine has been shown to react with methyl vinyl ketone to form 2-ethyl-5-methyl-A -l,2-oxaphospholen-2-oxide (25), which has been converted to (26) by chlorination in the presence of base. The same phosphine adds to methyl acrylate in the presence of acetic acid to give the phosphine oxide (27). Further examples have appeared of the reactions of the phenylhydrazones of methyl ketones with phosphorus trichloride to produce the heterocycles (28). 

Palladium-catalyzed bis-silylation of methyl vinyl ketone proceeds in a 1,4-fashion, leading to the formation of a silyl enol ether (Equation (47)).121 1,4-Bis-silylation of a wide variety of enones bearing /3-substituents has become possible by the use of unsymmetrical disilanes, such as 1,1-dichloro-l-phenyltrimethyldisilane and 1,1,1-trichloro-trimethyldisilane (Scheme 28).129 The trimethylsilyl enol ethers obtained by the 1,4-bis-silylation are treated with methyllithium, generating lithium enolates, which in turn are reacted with electrophiles. The a-substituted-/3-silyl ketones, thus obtained, are subjected to Tamao oxidation conditions, leading to the formation of /3-hydroxy ketones. This 1,4-bis-silylation reaction has been extended to the asymmetric synthesis of optically active /3-hydroxy ketones (Scheme 29).130 The key to the success of the asymmetric bis-silylation is to use BINAP as the chiral ligand on palladium. Enantiomeric excesses ranging from 74% to 92% have been attained in the 1,4-bis-silylation. 

Photolytic. Methyl vinyl ketone and methacrolein were reported as major photooxidation products for the reaction of 2-methyl-l,3-butadiene with OH radicals. Formaldehyde, nitrogen dioxide, nitric oxide, and HO2 were reported as minor products (Lloyd et al, 1983). Synthetic air containing gaseous nitrous acid and exposed to artificial sunlight (X = 300-450 nm) photo-oxidized 2-methyl-1,3-butadiene into formaldehyde, methyl nitrate, peroxyacetal nitrate, and a compound tentatively identified as methyl vinyl ketone (Cox et al, 1980). 

Mesityl oxide at a mercury cathode in acetate buffer affords a mixture of tail-to-tail and head-to-tail hydrodimers. The initally formed reduction products undergo further reactions so that 32 and 33 are isolated [106, 107, 108]. A low yield of the head-to-head glycol has been isolated from some reactions [109, 110, 111]. The structures of these products were confirmed in 1955 [112], Methyl vinyl ketone yields a mixture of tail-to-tail and head-to-head hydrodimers [113],... 

Elsewhere, Heaney et al. (313-315) found that alkenyloximes (e.g., 285), may react in a number of ways including formation of cyclic nitrones by the 1,3-APT reaction (Scheme 1.60). The benzodiazepinone nitrones (286) formed by the intramolecular 1,3-APT will undergo an intermolecular dipolar cycloaddition reaction with an external dipolarophile to afford five,seven,six-membered tricyclic adducts (287). Alternatively, the oximes may equilibrate to the corresponding N—H nitrones (288) and undergo intramolecular cycloaddition with the alkenyl function to afford five,six,six-membered tricyclic isoxazolidine adducts (289, R = H see also Section 1.11.2). In the presence of an electron-deficient alkene such as methyl vinyl ketone, the nitrogen of oxime 285 may be alkylated via the acyclic version of the 1,3-APT reaction and thus afford the N-alkylated nitrone 290 and the corresponding adduct 291. In more recent work, they prepared the related pyrimidodiazepine N-oxides by oxime-alkene cyclization for subsequent cycloaddition reactions (316). Related nitrones have been prepared by a number of workers by the more familiar route of condensation with alkylhydroxylamines (Scheme 1.67, Section 1.11.3). 

Scheme 1.64). The Ag(I)-mediated cyclization afforded dipole 306 for 1,3-dipolar cycloaddition with methyl vinyl ketone to yield adducts 307 and the C(2) epimer as a 1 1 mixture (48%). Hydrogenolytic N—O cleavage and simultaneous intramolecular reductive amination of the pendant ketone of the former dipolarophile afforded a mixture of alcohol 308 and the C(6) epimer. Oxidation to a single ketone was followed by carbonyl removal by conversion to the dithiolane and desulfurization with Raney nickel to afford the target compound 305 (299). By this methodology, a seven-membered nitrone (309) was prepared for a dipolar cycloaddition reaction with Al-methyl maleimide or styrene (301). 

Of the many studies of the autoxidation of butenes, few (5,11) have emphasized methyl vinyl ketone and methyl vinyl carbinol as major products. In the cumene hydroperoxide-initiated oxidation of 1-butene at 105°C. with 60 atm. of air, Chernyak (5) reported an average hourly rate of production of these two products approximately equal to the combined rates of formation of hydroperoxide and epoxide. The reported rates for hydroperoxide plus vinyl ketone and alcohol indicate that 60% of the products occur by abstraction, in agreement with Van Sickle (17). 

Biesenthal, T. A., and P. B. Shepson, Observations of Anthropogenic Inputs of the Isoprene Oxidation Products Methyl Vinyl Ketone and Methacrolein to the Atmosphere, Geophys. Res. Lett., 24, 1375-1378 (1997). 

Butenediol Methyl Vinyl Ketone Butylene Oxide Polybutene Di-N-Butyl Ether... 

MIDETR1ETHYLAMINE, 58, 122 Methyl thiohenzoate, 58, 41,43 Methyl vinyl ketone, 58, 162, 163, 164, 167 Moffat oxidation, 56, 99 Monochloroborane dicthylctherate, 58,... 

Improvements in the double Skraup synthesis of 1,7-phenanthroline from m-phenylenediamine now enable a yield of 70% to be achieved.163 The Skraup reaction continues to be used for the synthesis of 1,7-phen-anthrolines starting from the substituted 5-aminoquinolines. S-Chloro-6-hydroxy-1,7-phenanthroline (18) has been prepared in this way,164 and an improved synthesis of 6-hydroxy-1,7-phenanthroline was reported.165 As expected, the Skraup reaction on 5-aminoquinaldine affords 8-methyl-1,7-phenanthroline,166 not 2-methyl-1,7-phenanthroline as it was previously named.8 The extension of the Skraup reaction using methyl vinyl ketone instead of glycerol has been applied to 5-aminoquinoline to afford 4-methyl-1,7-phenanthroline.166 A related condensation using 2-hydroxymethylenecyclohexanone provides a route to benzo-substituted 1,7-phenanthrolines.167 7-Aminoquinoline with mesityl oxide in the presence of iodine gives 8,8,10-trimethyl-7,8-dihydro-l,7-phenanthroline (19).168... 

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