Methyl vinyl ketone, from oxidation

Navarro MA, Dusanter S, Hites RA, Stevens PS (2011) Radical dependence of the yields of methacrolein and methyl vinyl ketone from the OH-initiated oxidation of Isoprene under NOx-free conditions. Environ Sci Technol 45 923-929... 

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. 

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],... 

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... 

The reactivity profiles of the boronate complexes are also diverse.43 For example, the lithium methyl-trialkylboronates (75) are inert, but the more reactive copper(I) methyltrialkylboronates (76) afford conjugate adducts with acrylonitrile and ethyl acrylate (Scheme 16).44 In contrast, the lithium alkynylboronates (77) are alkylated by powerful acceptors, such as alkylideneacetoacetates, alkylidene-malonates and a-nitroethylene, to afford the intermediate vinylboranes (78) to (80), which on oxidation (peracids) or protonolysis yield the corresponding ketones or alkenes, respectively (Scheme 17).45a Similarly, titanium tetrachloride-catalyzed alkynylboronate (77) additions to methyl vinyl ketone afford 1,5-diketones (81).4Sb Mechanistically, the alkynylboronate additions proceed by initial 3-attack of the electrophile and simultaneous alkyl migration from boron to the a-carbon. 

Methyl vinyl ketone (entry 3) and the tert-butyl cation (entry 4) are also reactive toward complex 3. The naphthalenium complexes resulting from the addition of these electrophiles will add the conjugate base of dimethyl malonate (generated in situ from a combination of dimethyl malonate (DMM) and diisopropylethylamine (DIEA)) to complete the tandem additions. Oxidation of the resulting complexes yields cis-l,4-dihydronaphthalenes. The entire sequence of complexation, tandem addition, and demetalation employed for all entries in Table 4 can be performed using bench-top conditions (i.e., a non-inert atmosphere). 

Further research (22-24) has shown that butene oxidation can produce many selective reaction products (furan, acetaldehyde, and methyl vinyl ketone), which are not detected during butane oxidation. It cannot be assumed that the oxidation of butane and of the unsaturated reactants proceed along the same pathway. The kinetics data must be viewed with this point in mind, although butane activation is widely accepted to be the rate-determining step. The intermediates are capable of desorbing from the surface (as observed in the TAP investigations), but they do not, indicating that the further reactions occur more readily than desorption. 

Preparation of Monomers. Methyl vinyl ketone (MVK) was obtained from Pfizer Chemical Division, New York, and distilled to remove the inhibitor. Methyl isopropenyl ketone (MIPK) was prepared by the aldol condensation of methyl ethyl ketone and formaldehyde, according to the method of Landau and Irany 0. The major impurity in this monomer is ethyl vinyl ketone (5. The monomer was redistilled before use. 3 Ethyl 3 buten 2 one (EB) was prepared by the aldol condensation of methyl propyl ketone and formaldehyde. Ethyl vinyl ketone (EVK) was prepared by a Grignard synthesis of the alcohol, followed by oxidation to the ketone. t-Butyl vinyl ketone (tBVK) was prepared from pinacolone and formaldehyde by the method of Cologne (9). Phenyl vinyl ketone (PVK) was prepared fay the dehydrochlorlnatlon of 0 cbloro propiophenone (Eastman Kodak). Phenyl isopropenyl ketone (PPK) was prepared by the Mannich reaction using propiophenone, formaldehyde and dimethylamine HCl. 

Similar data have been obtained for the adsorption of but-l-ene and isobutene on copper(i) and copper(ii) oxides. Although the results are less clear cut than with the propene system, in general a similar pattern emerges. The reversibly adsorbed species has infrared bands characteristic of a 7r-bonded allyl species. Addition of oxygen to reversibly adsorbed but-l-ene at room temperature results in bonds characteristic of acrolein and acetaldehyde. Methyl vinyl ketone is only formed at higher temperatures. The adsorption of the major partial oxidation products on copper(i) oxide was also investigated. Metha-crolein behaves like acrolein and is reversibly adsorbed. Methyl vinyl ketone, however, mainly forms carboxylate and carbonate types of structures. This reflects the ease of oxidation of the partial oxidation product. The reason for the higher selectivities observed with the branched alkenes can thus be ascribed to the relative ease of oxidation of the partial oxidation product from the linear allene. 

---