Neohexene

To a mixture of 0.40 mol of neohexene ( commercially available) and 200 ml of dry diethyl ether 0.35 mol of bromine was added with cooling between -40 and -50°C. The diethyl ether and excess of neohexene were then completely removed by evaporation in a water-pump vacuum.In the second flask was placed a solution of 90 g of commercial KO-tert.-C9H9 (see Chapter IV, Exp. 4, note 2) in 250 ml of DMSO. The dibromo compound was added in five portions during 15 min from the dropping funnel after the addition of each portion the flask was swirled gently in order to effect homogenization. Much heat was evolved and part of the tert.-butylacetylene passed over. After the addition the flask was heated for 30 min in a bath at B0-100°C. 

Neohexene, synthesis of, 26 939-941 Neoisomenthol, 24 512, 513 Neomenthol, 24 512, 513 Neomethymycin, 15 272 Neomycin, bacterial resistance mechanisms, 3 32t... 

Above we have mentioned several heterogeneous applications such as the OCT process and SHOP. Neohexene (3,3-dimethyl-1-butene), an important intermediate in the synthesis of fine chemicals, is produced from the dimer of isobutene, which consists of a mixture of 2,4,4-trimethyl-2-pentene and 2,4,4-trimethyl- 1-pentene. Cross-metathesis of the former with ethene yields the desired product. The catalyst is a mixture of W03/Si02 for metathesis and MgO for isomerisation at 370 °C and 30 bar. The isobutene is recycled to the isobutene dimerisation unit [48],... 

Further important industrial applications of olefin metathesis include the synthesis of 3,3-dimethyl-l-butene ( neohexene , intermediate for the production of musk perfume) from ethene and 2,4,4-trimethyl-2-pentene, the manufacture of a,co-dienes from ethene and cycloalkenes (reversed RCM), and the ROMP of cyclooctene and norbomene to Vestenamer and Norsorex , respectively. 

Upon reaction with ethylene, neither supposed [(=SiO)2Ti(=CHCMe3)j nor [(=SiO)2Zr(=CHCMe3)] species produced neohexene, the expected metathetical exchange product Instead, oligomerization of ethylene was observed, in agreement with results reported for neopentylidenes of group 5 [50]. 

Reaction of p-cymene with 3,3-dimethyl-l-butene (neohexene) and a tertiary alkylhalide (as a hydrogen scavenger) in the presence of catalytic amounts of anhydrous aluminum halide in inert solvents produces a high yield of the hexamethyltetralin [159]. 

In the Phillips neohexene process147 2,4,4-trimethyl-2-pentene (8) is converted by cleavage with ethylene to neohexene (9) used in the production of a perfume musk. The starting material is commercial diisobutylene. Since it is a mixture of positional isomers (2,4,4-trimethyl-2-pentene and 2,4,4-trimethyl-l-pentene) and the latter (7) participates in degenerative metathesis, effective utilization of the process requires the isomerization of 7 into 8. A bifunctional catalyst system consisting of an isomerization catalyst (MgO) and a heterogeneous metathesis catalyst is employed 131... 

Dimethylbut-l-ene (neohexene), which is inactive to self-metathesis, undergoes cross-metathesis with internal alkenes to high conversion when catalysed by WCl6/Et20/Bu4Sn153. 

Titanaeyclobutane compound 5 [30] was isolated from the reaction of Tebbe reagent with d1-neohexene, Eq. (11)- On addition of dimethylalumimum chloride, the Tebbe reagent (partially deuterated) was recovered, Eq. (12). 

Phillips Neohexene Process Phillips operated since 1980 diisobutene+ethylene 1.4 kt/a neohexene isobutene recycled W03/Mg0/Si02 370°C 30 bar... 

Cyclohexene exists only as internal cw-olefin and is moderately reactive. In contrast, -hexene, regardless of whether charged as 1- or internal olefin or a mixture of these, is quickly isomerized to a near-equilibrium mixture containing some 5 to 10% of the isomer with terminal double bond, whose reactivity is about two orders of magnitude higher than those with internal ones. Accordingly, -hexene is more reactive than cyclohexene with only internal double-bond positions. Lastly, neohexene (3,3 -dimethyl-l-butene) has its double bond locked in the terminal position —no double bond can exist adjacent to a quaternary carbon atom—and so should have the highest reactivity if not sterically hindered. (This is an unsubstantiated prediction, as the hydroformylation reactivity of that olefin seems not to have been studied to date.)... 

Cross metathesis of ethylene with internal alkenes provides a facile route to terminal alkenes. A number of processes have been described that use this transformation however, the only products, besides neohexene,that appear to be important are the a,o>-dienes that result from metathesis of cyclic alkenes with an excess of eAylene. This family of compounds should find a wide variety of applications. 

A metathesis similar to OCT came on stream about the same time as the SHOP process. Ethenolysis43 of a mixture of 2,4,4-trimethyl-2-pentene and 2,4,4-trimethyl-1-pentene yields 3,3-dimethyl-l-butene (commonly called neohexene) plus isobutylene (equation 11.15). 

This process, now run by the Chevron Phillips Chemical Company, produces over a million pounds of neohexene annually. Neohexene is a raw material used... 

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