Methylpent-l-enes

When pent-2-ene 7 is treated with two equivalents of diethylamine, the terminal enaminc 13 is formed in 82% yield.33 The authors propose a base-catalyzed migration of the C=C bond with perfluoro(2-methylpent-l-ene) formed as an intermediate. 

Fig. 3.5. Relationship between log (retention time) and boiling point for a range of hydrocarbons on squalane at 43°C. A, aliphatics (and benzene) B, alicyclics, 1-4 = C5-Cg n-alkanes 5 = 2-methyl-butane 6 = 2-methylpentane 7 = 2,3-dimethylbutane 8-12 = C4-C8 1-olefins 13,15,17 = trans-(but-2-ene, pent-2-ene and hept-2-ene) 14,16,18 = e/s-(but-2-ene, pent-2-ene and hept-2-ene) 19 = 2-methylbut-l-ene 20 = 2-methylpent-l-ene 21 = 4-methylpent-l-ene 22 = 2-methylbut-2-ene 23 = cyclopentane 24 = cyclohexane 25 = methylcyclopentane 26 = methylcyclohexane 27 = cyclo-pentene 28 = cyclohexene 29 = 4-methylcyclohexane 30 = 1,3-butadiene 31, 32 = trans- and cis-1,3-pentadiene 33 = diallyl 34, 35 = trans- and c s-2-methyl-l,3-pentadiene 36 = cyclopentadiene ...

Only single insertions into an Al-C bond occur for propene and higher alkenes and this is utilized for catalytic dimerization of propene as illustrated in Scheme 3. Insertion of propene into an Al-C bond of "PrsAl followed by )3-hydride elimination yields an aluminum hydride and 2-methylpent-l-ene. Insertion of propene into the Al-H bond regenerates "PrsAl. Thermal cracking of 2-methylpent-l-ene gives isoprene, which is subsequently polymerized with a Ziegler-Natta catalyst to form the synthetic rubber, cA-1,4-polyisoprene. 

The treatment of l,5-dichloro-2-methylpent-l-ene (80) with butyllithium and, subsequently, with Me3SiCl at — 110 °C gives access to the 1-TMS-derivative (81) (equation 38)53. Trans-fi-TMS-styrene (84) is available by the reaction of bis(TMS)-methyllithium... 

Markownikoff addition. 2-Methylpent-l-ene allowed to react with tertAmiyl hydroperoxide and mercuric acetate with initial cooling and shaking, after 2 hrs. the volatiles removed by distillation in vacuo, and the residue digested repeatedly with coned, aq. NaCl -> l-diloromercuri-2-tert-butylperoxy-2-methylpentane. Y 19%. F. e., also hydroperoxymercuration with H2 2 s. E. Schmitz, A. Riedie, and O. Brede, J. pr. 312, 30 (1970) a-alkoxyketones from enolesters s. ibid. 312, 43 peroxy- and methoxy-mercuration of a,i -unsatd. ketones and esters s. A. J. Bloodworth and R. J. Bunce, Soc. (C) 1971, 1453. 

Ulman and Grubbs have measured the rates of reaction of G1 with a series of alkenes (Table 2.9). Methylation at the aUylic position led to a reduction in reaction rate of approximately two orders of magnitude, while methylation at the homoallylic position made little difference to the reaction rate. The reaction with fieo-hexene did not occur at aU, nor did the reaction with 2-methylpent-l-ene, showing that steric bulk in the wrong place can have a dramatic effect on the reaction rate. While this study explores the... 

In the first step, propylene is dimerized to 2-methylpent-l-ene by passage over a catalyst of tri-n-propylaluminium at about 200°C and 200 atmospheres. This product is then isomerized to 2-methylpent-2-ene by heating at 150—300°C in the presence of a silica-alumina catalyst. The final step in the process is the pyrolysis of the olefin to isoprene at 650—800°C in the presence of a free radical initiator such as hydrogen bromide. The isomerization step is necessary because pyrolysis of 2-methylpent-l-ene gives much poorer yields of isoprene than pyrolysis of 2-methylpent-2-ene. 

Vinylboronic acids, easily prepared by hydroboration of acetylenes, react with iodine monochloride at low temperatures to give good yields of -vinyl iodides (Scheme 31). This mild alternative to an earlier approach is compatible with hydroxy, alkoxy, and carbomethoxy groups. Following monocarbozirconation, treatment of 1-pentynyldimethylalane (50) with iodine gives l,l-di-iodo-2-methylpent-l-ene (51) in 92% yield. ... 

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