Oct-4-ene oxide

To a solution of potassium methoxide (0.2 mmol) in HMPA (10 ml) (CAUTION—CANCER SUSPECT AGENT), heated to 65°C, was added (E)-oct-4-ene oxide (1.2 mmol), then hexamethyldisilane (1.8 mmol) in HMPA (5ml), and the yellow mixture was stirred at 65°C for 3h. The cooled mixture was poured onto saturated brine, and extracted with pentane (2 x 25 ml). The combined organic extracts were dried and concentrated, to give oct-4-ene (1.15 mmol, 96%, 99 1 (Z) (E) by g.I.c.). 

Dimsyl anion 88 is known to add to styrene, and to 1,1-diphenylethylene in the presence of a base, forming 3-arylpropyl methyl sulfoxides121. Treatment of ( )-3,3-dimethyl thiacyclo-oct-4-ene-l-oxide 89 with n-BuLi gave exo-4,4-dimethyl-2-thiacyclo-[3.3.0]octane 2-oxide 90, a bicyclic addition product of the internal double bond. A similar cyclization was observed in the reaction of 91 with n-BuLi122. 

As with permanganate oxidations, a-hydroxy ketones can be formed as side products. In some cases, structural features make the osmium complex relatively unstable, and in an aqueous medium it can react with water to give a hydroxy-hydrate, which is then converted to an a-keto alcohol. Sharpless et al. developed a procedure that used tert-butyl hydroperoxide with a catalytic amount of osmium tetroxide,367 in the presence of tetraethylammonium hydroxide (EtqN" " OH ). The procedure gave improved yields of the cis-diol and a little a-hydroxyketone, as shown in the conversion of oct-(4 )-ene to a mixture of 258 and 259 in 73% yield. This method is more reliable for oxidation of tri- and tetrasubstituted alkenes than the Upjohn procedure. The reaction was not suitable for base sensitive alkenes, but later work showed that changing the solvent to acetone allowed the use of tetraethylammonium acetate (Et4NOAc) 68 for the hydroxylation of sensitive alkenes such as ethyl crotonate. 

The synthesis of bixin (533) requires the regiospecific introduction of a Z double bond. Attention was first focused on the total synthesis of (all- )-methylbixin (534) [35]. (3-Methylepichlorohydrin (180) was treated with sodium acetylide (68) to give the alcohol 181 which was transformed with dihydropyran and phosphorus oxychloride to the acetylenic compound 182. Condensation of two moles of 182 with oct-4-ene-2,7-dione (5) in the presence of PhLi resulted in the C2o-diol 183. Treatment with p-toluenesulphonic acid first in toluene gave the diether 184 and afterwards in ethanol led to the diol 185, which was oxidized with Mn02 to the dial 186. The Knoevenagel condensation with malonic acid (187) and methylation with diazomethane gave the diester 188, which was hydrogenated in the presence of Lindlar catalyst and isomerized with iodine to (all- )-methylbixin (534) in an overall yield of 0.04% referred to 180 (Scheme 41). 

Hydroxymethylmethyldiazirine (209 unprotonated) formed propionaldehyde as the sole product by thermal nitrogen extrusion 4-hydroxy-l,2-diazaspiro[2.5]oct-l-ene (218) formed a mixture of cyclohexanone (73%), cyclohexenol (21%) and cyclohexene oxide (5%). Thermal decomposition of difluorodiazirine (219) was investigated intensively. In this case there is no intramolecular stabilization possible. On heating for three hours to 165-180 °C hexafluorocyclopropane and tetrafluoroethylene were formed together with perfluorofor-maldazine 64JHC59). 

Benzonitrile oxide, generated by dehydrochlorination of benzohydroximoyl chloride, undergoes regio- and face-selective cycloadditions to 6,8-dioxabicyclo [3.2.1]oct-3-ene 108a yielding a 4 1 mixture of 4,5-dihydroisoxazoles 109 and 110. Both products have exo-stereochemistry, resulting from the approach of the nitrile oxide from the face opposite to the the methyleneoxy bridge. Structures of the adducts were determined by 1 H NMR spectroscopy and, in the case of compound 109, by X-ray diffraction analysis (275). 

Lead tetraacetate, oxidation of a hydrazone to a diazo compound, 50, 7 Lithio ethyl acetate, 53, 67 Lithium, reductions in amine solvents, 50, 89 Lithium aluminum hydride, reduction of exo-3,4-dichloro-bicyclo-[3.2.l]oct-2-ene to 3-chlorobicyclo[3.2.l]oct-2-ene, 51, 61... 

An unusual incorporation of iodine derived from the Na(lO ) used in RuClj/aq. Na(10 )/CCl -CH3CN was noted in the oxidation of the terminal alkene 2-allyl-2,5-dichloro-4-morpholino-cyclopent-4-ene-l,3-dione giving the iodohydrin 5 3,7-dichloro-l-P-hydroxy-3 3-iodomethyl-8-morpholino-2-oxabicyclo[3.3.0]-oct-7-en-6-one and its 3a-epimer. The iodine apparently derives from the formation of or T from the lOj" to which IO is reduced after the RuClj/IO " reaction (Fig. 3.21) [236]. 

The interaction between two disulfide units in a 2,3,5,5-tetrathiabicyclo[2.2.2] oct-7-ene type radical cation with transannular delocalization between the four sulphur atoms was established by ESR. This radical cation was persistent enough to be crystallized and analyzed by X-ray crystallography. Remarkably, this species was formed after oxidation of 3,4,5,6-bis(bicyclo[2,2,2]octeno)-l,2-... 

The most useful application of 3 is its use in photochemical [2+2] cycloadditions with alkenes and alkynes at the carbon-carbon double bond to afford bicyclo[4.2.0]octane-2,5-diones and bicyclo[4.2.0]oct-7-ene-2,5-diones in good to excellent yield.6 Since selenium dioxide oxidation of the resulting adducts furnishes the corresponding 3-ene-2,5-diones, diketone 3 can be regarded as a 1,4-benzoquinone equivalent leading to [2+2] cycloadducts at the carbon-carbon double bond. 

The sulfoxides and sulfones analogues can be named as oxides or dioxides, for example, 3-thiabicyclo[3.2.1.0 ]oct-6-ene 3-oxide 4, 6-thiabicyclo[3.1.0]hexane 6,6-dioxide 5, and 2,2,4,4-tetramethyl-3,4-dioxa-7-thiabicyclo[4.1.0]hept-l(6)-ene 7-oxide 7. These oxidized analogues are sometime named with the suffix episulfoxide or episulfone. 

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