2-Methyl-l-buten-3-one

Methyl Isopropyl Ketone. Methyl isopropyl ketone [563-80-4] (3-methyl-2-butanone) is a colorless Hquid with a characteristic odor of lower ketones. It can be produced by hydrating isoprene over an acidic catalyst at 200—300°C (150,151) or by acid-catalyzed condensation of methyl ethyl ketone and formaldehyde to 2-methyl-l-buten-3-one, foUowed by hydrogenation to the product (152). Other patented preparations are known (155,156). Methyl isopropyl ketone is used as an intermediate in the production of pharmaceuticals and fragrances (see Perfumes), and as a solvent (157). It is domestically available from Eastman (Longview, Texas) (47). 

Chemical Designations - Synonyms Isopropenyl methyl ketone 2-Methyl-l-butene-3-one Chemical Formula CH3COC(CH3)=CHi. 

Dehydrohalogenation Reactions. Quinoline is sometimes used as a base or solvent for dehydrohalogenation reactions because of its basic properties. A wide variety of substrates, ranging from very simple to quite complex compounds, have been effectively dehydrohalogenated with quinoline. For example, 3-bromo-3-methyl-2-butanone (1) underwent reaction with quinoline to give a mixture of products, 3-methyl-2-butanone (2) and 2-methyl-l-buten-3-one (3) (eq 1). ... 

METHYL ISOPROPENYL KETONE, INHIBITED 2-Methyi-l-butene-3-one Flammable Liquid, II 2 - 0... 

The formal substitution of one methyl, chloro or hydroxyl group at the allylic position of propene results into the reachvity order 1-butene > allyl chloride > aUyl alcohol. Methyl substitution on butenes also produces the expected ordering 2-methyl-2-butene > 2-methyl-l-butene > 3-methyl-1-butene (Table 18.8). 

Buten-2-one, 4-(5-methyl-2-furanyl)-, 4-(5-methyl-2-furyl)but-3-en-2-one, l-(5-methyl-2-furanyl)-l-buten-3-one [23120-57-2] ( )-[66434-99-9]... 

Attack of NO3 on isoprene apparently proceeds in much the same manner, but there is considerable controversy about the precise reaction pathway because of the variety of peroxy radicals that can be formed. The products, such as 4-nitroxy-2-methyl-l-butan-3-one and methacrolein, are consistent with the initial addition of NO3 to the terminal carbon atoms to form nitro-oxy-peroxy radicals in the presence of oxygen apparently the NO3 adds preferentially to position 1 (Fig. 12). 3-methyl-4-nitroxy-2-butenal was found as the main product in these experiments. The nitro-oxy-peroxy radicals can react with NO2, in the presence of O2, to yield thermally unstable nitroxy-peroxynitrate compounds. One particularly important feature of the addition of NO3 is the extent to which the initial adduct, which might eliminate NO2 to form an epoxide, is actually converted to the nitro-oxy-peroxy radicals in the atmosphere. 

In discussing processes in olefins, it is convenient to divide the reactions into two classes simple particle transfer and carbon-addition reactions. The relative importance of these two types of reaction is also dependent on the structure of the reactants. The presence of the isobutene type structure (CH2=C(CH3)CH2—) in either the reactant ion or neutral molecule favours the simple particle transfer reaction, mainly because of the large cross-section for the formation of parent-plus-one ions. The 2-butene neutral molecule is more like isobutene than 1-butene with regard to the relative importance of simple particle transfer and carbon addition reactions [284]. However, the magnitude of the cross-section for simple particle transfer reactions in 2-butene (2-P + 2-M reaction) is much closer to that in 1-butene (1-P + 1-M reaction) than to that in isobutene (iso-P + iso-M reaction) [284, 299]. The same is true for pentene isomers i.e. the cross-sections for simple particle transfer reactions in 1-pentene and 2-pentenes are almost the same and are much lower than that in 2-methyl-l-butene. The simple particle transfer cross-sections for other branched pentenes, i.e. 2-methyl-2-butene and 3-methyl-l-butene, are even smaller than those for 1- and 2-pentenes, while the proportion of transfer reactions is higher than the corresponding proportions for 1- and 2-pentenes. The proportion is, of course, highest for 2-methyl-l-butene which has the isobutene type structure. 

In attempts to circumvent these difficulties, a related but conceptually discrete tail-to-head construction protocol has recently been developed. For discussions of some intricate aspects, it is useful to distinguish two modes of oligoisoprenoid construction, that is, head-to-tail (H-to-T hereafter) and tail-to-head (T-to-H hereafter) modes, where the head and tail of the isoprene unit are defined as the disubstituted (head) and monosubstituted (tail) ends of a trisubstituted alkene moiety, respectively. Thus, the protocol developed in 1980 represents the H-to-T mode of isoprenoid construction. The recently developed T-to-H construction protocol entails one-pot homologation cycles using (E)- and (Z)-l,4-diiodo-2-methyl-l-butenes (1 and 2, respectively, in Scheme 3). More specifically, it involves (i) Pd-catalyzed... 

The first example of the ruthenium-catalyzed synthesis of amides from alcohols and amines was reported by Murahashi et al. in 1991 [82aj. The contrast results were obtained from the RuH2(PPh3)4-catalyzed reaction of 5-aminopentanol. Thus, piperidine was obtained in 79% yield, while similar treatment in the presence of a hydrogen acceptor of l-phenyl-l-buten-3-one gave piperidone in 65% yield (Eq. (7.36)). Recently, Williams reported the intermolecular amidation reaction of benzyl alcohols with amines in the presence of [Ru(p-cymene)Cl2]2 and 3-methyl-2-butanone [82bj. 

In Section 9.2, we looked at the reaction of symmetrically substituted 2,3-dimethyl-2-butene with hydrogen chloride (Fig. 9.2). In the formation of the carbocation, there was no choice to be made—only one cation could be formed. When the less symmetrical alkene 2-methyl-l-butene reacts with hydrogen... 

Except for the biochemical example just cited, the stmctures of all of the alcohols in Section 5.9 were such that each one could give only a single alkene by p elimination. What about elimination in alcohols such as 2-methyl-2-butanol, in which dehydration can occur in two different directions to give alkenes that are constitutional isomers Here, a double bond can be generated between C-1 and C-2 or between C-2 and C-3. Both processes occur but not nearly to the same extent. Under the usual reaction conditions 2-methyl-2-butene is the major product, and 2-methyl-l-butene the minor one. 

An equimolar mixture of 2-mercapto-3-pentanone and 1-amino-l-buten-3-one stirred whereupon after ca. 10 min. tbe temp, rises to 50-60°, tbe product isolated when tbe exothermic reaction has ceased and the mixture regained room temp. 5-methyl-4-ethyl-2-acetonyl-Zl -thiazoline (Y 78%) heated to 180° with distillation of the products 5-methyl-4-ethylthiazole (Y 92%). F. e. s. F. Asinger, L. Schroder, and S. Hoffmann, A. 64S, S3 (1961). 

By Claisen Rearangement In this route, 6-methyl-5-hepten-2-one is prepared by reaction of 3-methyl-l-buten-3-ol with isopropenylmethyl ether, followed by Claisen rearangement ... 

From Isobutylene and Formaldehyde In this process 6-methyl-5-hepten-2-one is prepared via isoprenol by isomerization of 2-methyl-l-hepten-6-one. The starting material can be prepared in two steps from isobutylene and formaldehyde. The formed 3-methyl-3-buten-l-ol reacts with acetone to yield the desired product... 

Bromination of isoprene using Br2 at —5 ° C in chloroform yields only /n j -l,4-dibromo-2-methyl-2-butene (59). Dry hydrogen chloride reacts with one-third excess of isoprene at —15 ° C to form the 1,2-addition product, 2-chloro-2-methyl-3-butene (60). When an equimolar amount of HCl is used, the principal product is the 1,4-addition product, l-chloro-3-methyl-2-butene (61). The mechanism of addition is essentially all 1,2 with a subsequent isomerization step which is catalyzed by HCl and is responsible for the formation of the 1,4-product (60). The 3,4-product, 3-bromo-2-methyl-1-butene, is obtained by the reaction of isoprene with 50% HBr in the presence of cuprous bromide (59). Isoprene reacts with the reactive halogen of 3-chlorocyclopentene (62). 

The carbocation formed on ionization of l-chloro-3-methyl-2-butene is the same allylic carbocation as the one formed on ionization of 3-chloro-3-methyl-l-butene and gives the same mixture of products. 

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