3-Ethyl-2-pentene, hydrogenation

Since a carbocation can add to an alkene to form a larger cation, under acidic conditions isobutylene can dimerize to form 2,4,4-trim ethyl -1 -pen ten e [107-39-1] and 2,4,4-trimethyl-2-pentene [107-40-4J, which can then be hydrogenated in the presence of nickel to form isooctane [540-84-1]. This reaction is no longer of commercial significance. 

Of more direct interest is the preparation of 3-ethylquinuclidine by this method (Prelog, Sogtaric and Gustak (1940)). Ethyl tetrahydropyranyl ketone (X R = tetrahydropyranyl in X to XIV) was condensed wiA ethyl brpmoacetate (XI) to give the hydroxy-acid ester (XII) which was dehydrated by potassium acid sulphate at 90° to ethyl 3-(tetrahydro-pyranyl-4)-pentenate (XIII) and this hydrogenated to tie corresponding... 

The chiral sites which are able to rationalize the isospecific polymerization of 1-alkenes are also able, in the framework of the mechanism of the chiral orientation of the growing polymer chain, to account for the stereoselective behavior observed for chiral alkenes in the presence of isospecific heterogeneous catalysts.104 In particular, the model proved able to explain the experimental results relative to the first insertion of a chiral alkene into an initial Ti-methyl bond,105 that is, the absence of discrimination between si and re monomer enantiofaces and the presence of diastereoselectivity [preference for S(R) enantiomer upon si (re) insertion]. Upon si (re) coordination of the two enantiomers of 3-methyl-l-pentene to the octahedral model site, it was calculated that low-energy minima only occur when the conformation relative to the single C-C bond adjacent to the double bond, referred to the hydrogen atom bonded to the tertiary carbon atom, is nearly anticlinal minus, A- (anticlinal plus, A+). Thus one can postulate the reactivity only of the A- conformations upon si coordination and of the A+ conformations upon re coordination (Figure 1.16). In other words, upon si coordination, only the synperiplanar methyl conformation would be accessible to the S enantiomer and only the (less populated) synperiplanar ethyl conformation to the R enantiomer this would favor the si attack of the S enantiomer with respect to the same attack of the R enantiomer, independent of the chirality of the catalytic site. This result is in agreement with a previous hypothesis of Zambelli and co-workers based only on the experimental reactivity ratios of the different faces of C-3-branched 1-alkenes.105... 

The hydroformylation of several olefins in the presence of Co2(CO)8 under high carbon monoxide pressure is reported. (S)-5-Methylheptanal (75%) and (S)-3-ethylhexanal (4.8%) were products from (- -)(S)-4-methyl-2-hexene with optical yields of 94 and 72%, respectively. The main products from ( -)(8)-2,2,5-trimethyl-3-heptene were (S)-3-ethyl-6,6-di-methylheptanal (56.6%) and (R)-4,7,7-trimethyloctanal (41.2%) obtained with optical yields of 74 and 62%, respectively. (R)(S)-3-Ethyl-6,6-dimethylheptanal (3.5% ) and (R)(S)-4,7,7-trimethyloctanal (93.5%) were formed from (R)(S)-3,6,6-trimethyl-l-heptene. (+/S)-l-Phenyl-3-methyl-1-pentene, under oxo conditions, was almost completely hydrogenated to (- -)(S)-l-phenyl-3-methylpentane with 100% optical yield. 3-(Methyl-d3)-l-butene-4-d3 gave 4-(methyl-d3)pentarwl-5-d3 (92%), 2-methyl-3-(methyl-d3)-butanal-4-d3 (3.7%), 3-(methyl-d3)pentanal-2-d2,3-d1 (4.3%) with practically 100% retention of deuterium. The reaction mechanism is discussed on the basis of these results. 

Acyclic and cyclic allenes are converted to alkenes at 60 °C under atmospheric pressure of hydrogen with [RhCl(PPh3)3]. 1,2-Nonadiene (26), 3-ethyl-1,2-pentadiene and 1,2-cyclotridecadiene are hydrogenated to give cts-2-nonene (27), 3-ethyl-2-pentene and cyclotridecene (cis trans = 85 15), respective-... 

With alkynes hydrocarbonylative coupling leads to unsaturated ketones with exclusive cis addition of hydrogen and the acyl group. Thus, rhodium carbonyl catalyzed carbonylation of acetylenes and ethene with carbon monoxide and hydrogen stereospecifically leads to a./l-un-saturated ethyl ketones by cross hydrocarbonylation4- 5, e.g., diphenylacetylene with ethene in the presence of Rh4(CO)l3 gives ( )-1.2-diphenyl-l-penten-3-one in 91 % yield5. 

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