2-Cydohexene

Free cydohexene from peroxides by treating it with a saturated solution of sodium bisulphite, separate, dry and distil collect the fraction, b.p. 81-83°. Mix 8 -2 g. of cycZohexene with 55 ml. of the reagent, add a solution of 15 mg. of osmium tetroxide in anhydrous butyl alcohol and cool the mixture to 0°. Allow to stand overnight, by which time the initial orange colouration will have disappeared. Remove the solvent and unused cydohexene by distillation at atmospheric pressure and fractionate the residue under reduced pressure. Collect the fraction of b.p. 120-140°/15 mm. this solidifies almost immediately. Recrystallise from ethyl acetate The yield of pure cis-l 2 cydohexanediol, m.p. 96°, is 5 0 g. 

FIGURE 11 2 Heats of hy drogenation of cydohexene 1 3 cydohexadiene a hypo thetical 1 3 5 cydohexa triene and benzene All heats of hydrogenation are in kilojoules per mole... 

Ch1oro-3-methyl- 3-Chloro-1-methyl-cydohexene cyclohexene... 

One of the earliest useful methods for asymmetric opening of meso-epoxides with sulfur-centered nucleophiles was reported by Yamashita and Mukaiyama, who employed a heterogeneous zinc tartrate catalyst (Scheme 7.10) [20]. Epoxides other than cydohexene oxide were not investigated, and the enantioselectivity depended strongly on the identity of the thiol. 

Scheme 12.12 Synthesis of heterocycles from cydohexene oxide.

In contrast, the titanium(IV)-catalyzed condensation of l-(trimethylsilyloxy)cydohexene and ( )-3-(2-nitro-l-propenyl)furan proceeded in the reverse stereochemical sense and gave three diastereomeric 1,2-oxazine 2-oxides lb, 2b and 3b in a ratio of 1 4 1. The major diastereomeric adducts 2b and lb were converted to the. syn-ketonc 4b upon hydrolysis16. 

In another signiflcant example published in the same period, Guanti and coworkers described the desymmetrization of the meso cydohexene diester (3) to give the hemiester (4), whose enantiomeric excess increased from 55 to 96% when moving from plain buffer to the same buffer containing 10% v/v t-BuOH (Scheme 1.2 and Table 1.2 [8]). 

Cycloalkene Hydrogenation Investigated in Micro Reactors Cas/liquid reaction 16 [CL 16] Catalytic hydrc enation of cydohexene... 

Drivers for Performing the Cydohexene Hydrc enation and Dehydrc enation... 

Beneficial Micro Reactor Properties for Cydohexene Hydrc enation and Dehydrogenation... 

In a 500 ml. three-necked flask, equipped with a mechanical stirrer, thermometer and dropping funnel, place 300 ml. of 88-90 per cent, formic acid and add 70 ml. of 30 per cent, hydrogen peroxide. Then introduce slowly 41 g. (51 ml.) of freshly distilled cydohexene (Section 111,12) over a period of 20-30 minutes maintain the temperature of the reaction mixture between 40° and 45° by cooling with an ice bath and controlling the rate of addition. Keep the reaction mixture at 40° for 1 hour after all the cydohexene has been added and then allow to stand overnight at room temperature. Remove most of the formic acid and water by distO-lation from a water bath under reduced pressure. Add an ice-cold solution of 40 g. of sodium hydroxide in 75 ml. of water in small portions to the residual mixture of the diol and its formate take care that the tempera-... 

The effect of microwave irradiation on the catalytic hydrogenation, dehydrogenation, and hydrogenolysis of cydohexene was studied by Wolf et al. [81]. Optimum conditions for benzene formation were a hydrogen flow, N-CaNi5 catalyst, atmospheric pressure, and 70 s irradiation time. Cydohexane was the main product when the irradiation time was 20 s, or in a batch/static system. 

H. Yoshizake, H. Satoh, Y., Satoh, S. Nukui, M. Shibasaki, M. Mori, Palladium-Mediated Asymmetric Synthesis of Cfs-3,6-Disubstituted Cydohexenes. A Short Total Synthesis of Optically Active (+)-Y-Lycorane , J. Org Chem 1995, 60, 2016-2021. 

A geometric isomer of the vinylallene mentioned above also undergoes [4 + 21-cycloaddition with butadiene to furnish a cydohexene derivative in 90% yield with excellent diastereomeric purity (>99 1). The preferred formation of a jt-allylpalla-dium complex from the axially oriented complex accounts for the trans selectivity (Scheme 16.79) [89]. 

In an approach by Jung and Nishimura, the assembly of the dysidiolide decalin skeleton 54 was deemed possible via an intermolecular Diels-Alder reaction between cydohexene 52 and dienophile 53 [14]. Based on precedent established by Wulff et al. [15] [where Z = C(OCH3)=Cr(CO)5], the cycloaddition should give predominantly the exo isomer as shown (Scheme 19.12). However, all attempts to effect the cydoad-dition simply gave recovery of starting material. It was reasoned that steric hindrance was to blame. The steric hindrance assodated with the dienophile was decreased by replacing one of the methyl groups with another double bond in the... 

Evidence for the generation of these reactive intermediates was obtained from a study of the effect of added cydohexene on the sonication of chloroform. The presence of free radicals in the system was confirmed by the appearance of chlorocydohexane as a product and by the increased rate of decomposition of CHCI3 in the presence of cyclohexene. The increased decomposition rate is a consequence of the presence, in the cavitation bubble, of the alkene which mops up the Cl radical as it is formed and prevents the regeneration of chloroform - i. e. the kinetic steps in Scheme 3.4 are driven from left to right. Carbene intermediates are implicated by the formation of tricyclic compounds such as (1) via dichlorocarbene addition to cydohexene. 

Relative to cydohexene - 100. Data from Renzetti and Doyle."Data from Ptagerer of. Data from Groblicki and Nebel. Data from Wilson et of. Data firom O Brien Data from Grotjean (unpublished data). Data from Glasson and Tuesday nitric oxide photooxidatkm rates. 

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