2.2- Dimethyl-3-butenal

The 0/7/fo-alkylation of aromatic ketones with olefins can also be achieved by using the rhodium bis-olefin complex [C5Me5Rh(C2H3SiMe3)2] 2, as shown in Equation (9).7 This reaction is applied to a series of olefins (allyltrimethyl-silane, 1-pentene, norbornene, 2,2 -dimethyl-3-butene, cyclopentene, and vinyl ethyl ether) and aromatic ketones (benzophenone, 4,4 -dimethoxybenzophenone, 3,3 -bis(trifluoromethyl)benzophenone, dibenzosuberone, acetophenone, />-chloroacetophenone, and />-(trifluoromethyl)acetophenone). 

The condensation of the cinnamaldehyde derivative (18) with ethoxycarbonyl-pentyltriphenylphosphorane in DMF gave a mixture of tram-trans- and trans-cis-products.22 A general method to prepare l-substituted-m-9-alkenes (19), using a stereoselective Wittig reaction, has been described.23 2,2-Dimethyl-3-butenal (20)... 

When either an alcohol or an amine function is present in the alkene, the possibility for lactone or lactam formation exists. Cobalt or rhodium catalysts convert 2,2-dimethyl-3-buten-l-ol to 2,3,3-trimethyl- y-butyrolactone, with minor amounts of the 8-lactone being formed (equation 51).2 In this case, isomerization of the double bond is not possible. The reaction of allyl alcohols catalyzed by cobalt or rhodium is carried out under reaction conditions that are severe, so isomerization to propanal occurs rapidly. Running the reaction in acetonitrile provides a 60% yield of lactone, while a rhodium carbonyl catalyst in the presence of an amine gives butane-1,4-diol in 60-70% (equation 52).8 A mild method of converting allyl and homoallyl alcohols to lactones utilizes the palladium chloride/copper chloride catalyst system (Table 6).79,82 83... 

Similarly, 56 reacts with sodium methoxide to give small quantities of the methoxymethyl analog of 56. In the same way, treatment of dichloro(2,2-dimethyl-3-buten-l-yl methyl sulfide)palladium(II) with CH2N2 gives the expected chloromethyl complex and a cyclopropanation product. 

Olefinic alcohols are best prepared by the action of lithium aluminum hydride on the corresponding acid or ester as in the preparation of 3-penten-l-ol (75%). The double bond may be in the a,/S-position to the ester group, The Bouveault-Blanc procedure has also been used with success for reduction of nonconjugated olefinic esters. The addition of the sodium to an alcoholic solution of the ester is superior to the reverse addition of. the ester to sodium in toluene for the preparation of 2,2-dimethyl-3-buten-l-ol (62%). Selective catalytic hydrogenation is inferior. Large amounts of catalyst are required, and the products contain saturated alcohols. ... 

The dimerization of propene has been extensively studied because the propene dimers are of considerable interest as fuel additives and as starting materials for the preparation of monomers (4, 48, 49, 101). The reaction course can be controlled to give methylpentenes, 2,3-dimethyl-butenes (2, 4, 7, 47, 51), or hexenes (44-46) as the main products. 

This discussion is certainly an over-simplification. Unfortunately there are no detailed experimental results for this reaction under strictly homogeneous conditions, but even with heterogeneous catalysts (e.g., AlCl3 and Ni [13]) only mixtures of branched paraffins, naphthenes and polyenes of low molecular weight are obtained. If isomerisation is slower than propagation, as indicated, e.g., by the experiments of Meier [5] on the polymerisation of 3,3-dimethyl butene-1, this would modify in detail but would not invalidate the above general conclusions. 

Dimethyl butene and Derivatives Dimethy(butene, C6H12 mw 84.16- Three Isomers are known ... 

Di(nitrotomethyl) -butene-1. See under Dimethyl-butene in this Vol, p D133L-L... 

The Arrhenius parameters for the gas-phase unimolecular structural isomerizations of 1,1,2-trimethylcyclopropane28 to three isomeric methylpentenes and two dimethyl-butenes, and of 1,1,2,2-tetramethylcyclopropane29 to 2,4-dimethylpent-2-ene have been determined over a wide range of temperatures. Despite previous reports on substantial decreases in activation energies for structural isomerizations of methyl-substituted cyclopropanes, this study has revealed that the trend does not continue beyond dimethylcyclopropane isomerization. 

One of the industrially important dimerization reactions that involves the use of homogeneous catalysts is the dimerization of propylene. Dimerization of propylene produces mixtures of the isomers of methyl pentenes, hexenes, and 2,3-dimethyl butene and is practiced by the Institut Francis du Petrole (IFP), Sumitomo, and British Petroleum (BP). The methyl pentenes and hexenes are used as gasoline additives. Dimethylbutene is used in the fragrance and the agrochemical industries. 

The equilibria present between olefins such as styrene, allylic esters, or 3,3-dimethyl butene-1 and palladium(II) acetate in acetic acid, have recently been studied 212). In the rate of acetate concentrations in which the acetate-bridged dimer [Na2Pd2(OAc)e] is the main species (Section II, A, 2), some peculiar results were observed. When olefin was added to the solution, a rapid change in spectra occurred followed by a slower change. The fast equilibrium is... 

N1(R2-Rx R1 R2 SacR3Sac)PLxL2L3 R3 PLW X X C6 % Dimethyl -butenes Produces Methyl -pentenes Hexenes % Higher 01 igomers... 

Ethyl-vinyl-ether + 3-Hydroxy-2,3-dimethyl-buten... 

Tctramethyl-3-tert.-butyl-.. . 7,7,10 J0-Tetramethyl-4-tert.-butyl-tri-cydo[4.4.0.02 dean-iP) +2,2,5,5-Tetramethyl-7-(3,3-dimethyl-buten- (l)-yl-bicydo[4.2.0 ]octen-(P) (17 83) — ... 

Praparativ interessant ist die nur bei direkter Anregung eintretende Synthese von Octamefhyl-cyclobutan (30%) aus 2,3 - Di me th y 1-buten - (2 )2. Dagegen liefert die mit Aceton sensibilisierte Reaktion 2,3,3,5,6-Pentamethyl-heptadien-(1,5) (4% d.Th.) und 2,3,6,7-Tetramethyl-octadien-(2,6) (2% d.Th.). Neben diesen Produkten der oxidativen Dimerisie-rung wurden funf versehiedene 1 1-Addukte zwischen 2,3-Dimethyl-buten-(2) und Aceton isoliert3. 

Das gleiche Cyclobutan-Dcrivat I laBt sich aueh durch Belichtung von 2,3-Diphenyl-Acrylsaure in 2,3-Dimethyl-buten-(2) mit 67%iger Ausbeute gewinnen. Dabei ist das /3-Lacton II Zwischenprodukt3. Durch Oxidation von I (N-Brom-succinimid-Methode) wird 3,3,4,4-Tetramethyl-l,2-diphenyl-cyclobuten (III 80% d.Th.) zuganglich. 

Dimethyl-buten-(2)8, 5-Methyl-2,3-dihydro-furan7, 3,4-Dihydro-2H-pyran8, Benzo-thiophcn9 und 2-Hydroxy-5,6,7,8-t.etrahydro-chinolin1 auizutreten, jedoch wurden intramolekulare Folgeadditionen bekannt11. 

In Gegenwart von 2,3-Dimethyl-buten-(2) bildefc 2-Oxo -1, 2-di hydro-chin olin neben 90% des Dimeren Vila noch 2-Oxo-9,9,10,10-tetramethyl-(benzo-3-aza-bicyclo[4.2.0] octen-(4)y (VIII 9,4% d.Th.)3 ... 

Photolysiert man 2-Oxo-2H-chromenin 1,4-Dioxan mit Benzophenon unter Zusatz von 2,3-Dimethyl-buten-(2), Cyclopenten oder 1,1-Diathoxy-athylen, so... 

---