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Alkylation with 2-methyl-2-butene

The carbopalladation is extended to homoallylic amines and sulfides[466. Treatment of 4-dimethylamino-l-butene (518) with diethyl malonate and Li2PdCl4 in THF at room temperature leads to the oily carbopalladated complex 519, hydrogenation of which affords diethyl 4-(dimethylamino) butylmalonate (520) in an overall yield of 91%. Similarly, isopropyl 3-butenyl sulfide (521) is carbopalladated with methyl cyclopentanonecarboxylate and Li2PdCl4. Reduction of the complex affords the alkylated keto ester 522 in 96% yield. Thus functionalization of alkenes is possible by this method. [Pg.96]

Electrophilic attack on the sulfur atom of thiiranes by alkyl halides does not give thiiranium salts but rather products derived from attack of the halide ion on the intermediate cyclic salt (B-81MI50602). Treatment of a s-2,3-dimethylthiirane with methyl iodide yields cis-2-butene by two possible mechanisms (Scheme 31). A stereoselective isomerization of alkenes is accomplished by conversion to a thiirane of opposite stereochemistry followed by desulfurization by methyl iodide (75TL2709). Treatment of thiiranes with alkyl chlorides and bromides gives 2-chloro- or 2-bromo-ethyl sulfides (Scheme 32). Intramolecular alkylation of the sulfur atom of a thiirane may occur if the geometry is favorable the intermediate sulfonium ions are unstable to nucleophilic attack and rearrangement may occur (Scheme 33). [Pg.147]

Catalytic asymmetric methylation of 6,7-dichloro-5-methoxy-2-phenyl-l-indanone with methyl chloride in 50% sodium hydroxide/toluene using M-(p-trifluoro-methylbenzyDcinchoninium bromide as chiral phase transfer catalyst produces (S)-(+)-6,7-dichloro-5-methoxy-2-methyl-2--phenyl-l-indanone in 94% ee and 95% yield. Under similar conditions, via an asymmetric modification of the Robinson annulation enqploying 1,3-dichloro-2-butene (Wichterle reagent) as a methyl vinyl ketone surrogate, 6,7 dichloro-5-methoxy 2-propyl-l-indanone is alkylated to (S)-(+)-6,7-dichloro-2-(3-chloro-2-butenyl)-2,3 dihydroxy-5-methoxy-2-propyl-l-inden-l-one in 92% ee and 99% yield. Kinetic and mechanistic studies provide evidence for an intermediate dimeric catalyst species and subsequent formation of a tight ion pair between catalyst and substrate. [Pg.67]

It is important to note that, while the primary product Cg carbenium ions that are formed (after reaction with 2-butene or 1-butene) are secondary, they can undergo hydride shift or methyl shift and form a tertiary carbenium ion in each case. In that case the driving force is diminished for either of the two tertiary Cg carbenium ions to abstract a hydride ion from i-butane since this now becomes a transition from a large tertiary carbenium ion to a smaller tertiary carbenium ion. Nevertheless, this hydride transfer can still occur due to the high ratio of i-butane to tertiary Cg carbenium ion that exists in the reaction medium. At the same time the tertiary Cg carbenium ion may get alkylated with another butylene molecule to make the more stable C12 carbenium ion, which would then lead to heavies. [Pg.452]

Ir-catalyzed alkylation with a nitro compound was applied in a synthesis of flS,2R)-tra s-2-phenylcyclopentanamine, a compound with antidepressant activity (Scheme 9.41) [45]. The reaction of cinnamyl methyl carbonate with 4-nitro-l-butene gave the substitution product with 93% ee in 82% yield. A Grubbs I catalyst sufficed for the subsequent RCM. Further epimerization with NEts yielded a trans-cyclopentene in 83% yield via the two steps, while additional reduction steps proceeded in 90% yield. [Pg.245]

Boddy and Robb have also studied the reactions of hydrogen atoms with propylene (11) and with 2-butene and isobutene (12). In all these reactions they observed decomposition of the hot alkyl radicals and also suggested an enhanced abstraction of hydrogen from the parent olefins by the hot radicals. The reaction with propylene appeared to be complicated by the ocurrence of a number of side reactions. One of the isolated products was 4-methyl-l-pentene, indicating the presence of allyl radicals, which the authors postulated to be formed in the reaction... [Pg.155]

Enamines derived from /3-diketones can be alkylated only with difficulty, and the structure of the products varies.222 Thus, Kochetkov,203 on treatment of 4-dimethylamino-3-buten-2-one with methyl... [Pg.190]

These findings are in agreement with Friedman and Morritz s (169) data which indicate that when benzene was alkylated with 3-methyl-butene-1 and A1C13 catalyst at 21° C. largely 2-phenyl-3-methylbutane formed (1,2 reaction) whereas at —40 °C. almost exclusively 2-phenyl-2-methylbutane was obtained (1,3 reaction). [Pg.534]

This sequence of reactions consists of an alkylation of a 1,3-diketone, followed by a Robinson annulation. The carbon-carbon double bond appears where the second carbonyl group of the diketone used to be and is the site of the ring-forming aldol reaction. A Michael reaction between the diketone and the Michael acceptor 3-buten-2-one adds the carbon atoms used to form the second ring, and an alkylation with CH3I adds the methyl group. [Pg.630]

Another route to (+)-19 nortestosterone (73) started from 2-methyl-l,3 cyclopentanedione (74). The asymmetric aldol condensation of the Michael adduct using L-phenylalanine produced the optically active enone (75). The PdCh-catalyzed oxidation yielded crystalline trione (76) in 77% ee, which was recrystallized as an optically pure form. Reduction of the double bond and aldol condensation afforded the desired cd rran.r-fused ketone (77). The construction of the A-ring was carried out by alkylation with 4-bromo-l-butene to give (78), the palladium-catalyzed oxidation, and aldol condensation to give the optically active (+)-19-nortestosterone (73 Scheme 22). ... [Pg.461]

The reaction of the. coal polyanion with methyl iodide occurs at least fivefold more rapidly than the reaction with butyl or octyl iodide, as judged by the rate of precipitation of potassium iodide. However, the results shown in the table reveal that there are only very minor differences in the solubility of the reaction products. In addition, we observed that the coal polyanions prepared from the insoluble residues of the first alkylation reaction were considerably more reactive. These polyanions reacted very rapidly with methyl iodide and reacted with butyl iodide to produce butene-1. [Pg.213]

Iso-butane is a highly demanded chemical in the refinery industry for the production of alkylates (by alkylation with butenes), and methyl tert-butyl ether (MTBE) (from isobutene and methanol), both important additives for reformulated gasolines. n-Butane isomerization is performed over platinum supported on chlorinated alumina. The chlorine compound which is continuously supplied to the feed in order to maintain the activity [1] is harmful to the environment. [Pg.1003]

Sequential alkylation of the lithium enolate of 897 with methyl iodide and then allyl bromide furnishes dialkylated malate 938 with 96 4 diastereoselectivity. The hydroxyl group is removed via a xanthate ester to give 939, which is then alkylated with 4-bromo-l-butene to give 940 as the major isomer. The mixture is hydrolyzed with base and heated with urea to yield imides 941 and 942 in a 3 1 ratio. After isolation of pure 941 by crystallization, the remaining undesired diastereomer 942 is epimerized to 941 with potassium tert-hutoxide. Oxidation of 941 with ruthenium tetroxide-sodium periodate and esterification of the resulting acids furnishes imide 943. This sequence has produced more than 10 g of 943 in a single run. [Pg.282]

Olah et al. reported the triflic acid-catalyzed isobutene-iso-butylene alkylation, modified with trifluoroacetic acid (TFA) or water. They found that the best alkylation conditions were at an acid strength of about//q = —10.7, giving a calculated research octane number (RON) of 89.1 (TfOH/TFA) and91.3 (TfOH/HaO). Triflic acid-modified zeohtes can be used for the gas phase synthesis of methyl tert-butyl ether (MTBE), and the mechanism of activity enhancement by triflic acid modification appears to be related to the formation of extra-lattice Al rather than the direct presence of triflic acid. A thermally stable solid catalyst prepared from amorphous silica gel and triflic acid has also been reported. The obtained material was found to be an active catalyst in the alkylation of isobutylene with n-butenes to yield high-octane gasoline components. A similar study has been carried out with triflic acid-functionalized mesoporous Zr-TMS catalysts. Triflic acid-catalyzed carbonylation, direct coupling reactions, and formylation of toluene have also been reported. Tritlic acid also promotes transalkylation and adaman-tylation of arenes in ionic liquids. Triflic acid-mediated reactions of methylenecyclopropanes with nitriles have also been investigated to provide [3 + 2] cycloaddition products as well as Ritter products. Tritlic acid also catalyzes cyclization of unsaturated alcohols to cyclic ethers. ... [Pg.504]

The hydroformylation of 2-butene under non-isomerizing conditions produces selectively 2-methylbutanal [36], which can be converted in the presence of an acid, such as boron phosphate, into isoprene (Scheme 4.6) [36a, 37]. Oxidation and subsequent esterification with ethanol opens up access to alkyl 2-methyl butanoates, which are important aromatic ingredient of perfumes and liqueurs. For example, Givaudan SA has commercialized ethyl methyl-2-butyrate as a modifier in floral accords or in combination with fruity esters. [Pg.290]

Other Higher Oleiins. Linear a-olefins, such as 1-hexene and 1-octene, are produced by catalytic oligomerization of ethylene with triethyl aluminum (6) or with nickel-based catalysts (7—9) (see Olefins, higher). Olefins with branched alkyl groups are usually produced by catalytic dehydration of corresponding alcohols. For example, 3-methyl-1-butene is produced from isoamyl alcohol using base-treated alumina (15). [Pg.425]


See other pages where Alkylation with 2-methyl-2-butene is mentioned: [Pg.450]    [Pg.29]    [Pg.152]    [Pg.263]    [Pg.825]    [Pg.34]    [Pg.205]    [Pg.216]    [Pg.263]    [Pg.133]    [Pg.180]    [Pg.36]    [Pg.142]    [Pg.253]    [Pg.551]    [Pg.203]    [Pg.1196]    [Pg.601]    [Pg.189]    [Pg.14]    [Pg.269]    [Pg.277]    [Pg.194]    [Pg.427]    [Pg.432]    [Pg.65]   
See also in sourсe #XX -- [ Pg.58 ]




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2-Methyl-2-butenal

2-Methyl-2-butene

3-Methyl-2-buten

Alkyl-methyl

Butene-1 alkylation

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