Norbomene oxide reduction

Reduction of epoxides. Hallsworth and Henbest (1,579,refs. 12 and 13)found that some steroidal epoxides, which were unreactive to lithium aluminum hydride, are easily reduced with a large excess of lithium in ethylamine. However, some olefin is also formed in some cases. Brown et al.1 now report that the combination of lithium and ethylenediamine at 50° is excellent for reduction of labile epoxides of bicyclic ketones, which are reduced only slowly by lithium aluminum hydride and usually with some extensive rearrangement. They chose ethylenediamine rather than ethylamine because the reduction is less vigorous in ethylenediamine than in ethylamine and thus easier to control. Also isolation of the alcohol is simplified because ethylenediamine is very soluble in water and only slightly soluble in ether, whereas ethylamine is miscible both in water and in ether. By this procedure, norbomene oxide (1) is reduced to pure ejco-norbomanol (2) in 87% yield (isolation). Analysis by glpc indicated that two rearranged alcohols (3, 4) are formed to a minor extent and that (2) is formed in 99.3% yield. 

Another example of transient formation of a palladacycle is the Pd-mediated ortho-alkylation and ipso-vinylation of aryl iodides depicted in Scheme 8.23. In this multicomponent reaction the ability of norbomene to undergo reversible arylation and palladacycle formation is exploited. This reaction also illustrates that aryl halides undergo oxidative addition to Pd faster than do alkyl halides, and that aryl-alkyl bond-formation by reductive elimination also proceeds faster than alkyl-alkyl bond-formation. The large excess of alkyl iodide used in these reactions prevents the formation of biaryls. Benzocyclobutenes can also be formed in this reaction, in particular when the alkyl group on the aryl iodide is sterically demanding or when a secondary alkyl iodide is used [161]. 

Examples of C(sp )-0 reductive elimination of olefin oxides from Pt center have been reported recently (Fig. 12) [33]. In the case of Pt oxetanes derived from strained cycloolefins, norbomene and cyclooctene, the elimination reactions can proceed readily at 40 60°C in a number of solvents and even in the solid state. The reaction is highly stereoselective formation of a single isomer of an olefin oxide is observed for norbomene. Importantly, as for complexes 9 and 14 (Fig. 8), the reactivity of the Pt oxetane 19 with an alkyl ligand trans- to the sulfonate is much higher than that of an isomeric compound 18 where the pyridine ligand, a poorer leaving group is trans- to the alkyl. 

Khusnutdinova JR, Newman L, Zavalij PY et al (2008) Direct C(ip )-0 reductive elimination of olefin oxides from Pt" -oxetanes prepared by aerobic oxidation of Pt olefin derivatives (Olefin = cw-Cyclooctene, Norbomene). J Am Chem Soc 130 2174—2175... 

Reaction of norbomene (176) with the organoborane 177 afforded the doubly alkenylated product 178. Although no mechanism was given, the first step seems to be the alkenylation of Pd(OAc)2 with 177, or transmetallation of 177 with Pd(OAc)2 to give 179 (which corresponds to 173). Then insertion of norbomene took place to afford 180. Since there is no jS-H syn to Pd, /3-H elimination is impossible. Therefore transmetallation with 177 and reductive elimination occur to give rise to the doubly alkenylated product 178. Chloroacetone was used as a good oxidant of Pd(0), since Cu(II) salts gave poor results in this reaction [11]. 

The latter readily undergo reductive elimination leading to ort/to-substituted palla-dium(Il) complexes, which cyclize again. Oxidative addition of a second molecule of RX and reductive elimination affords the o,o -disubstituted paUadium(lI) complex from which norbomene is deinserted owing to the unfavorable equihbrium (Scheme 9). 

In the presence of base, the C—H bond adjacent to the nitrogen atom is involved in the formation of cyclopaUadated intermediate C. In the second stage of the catalytic cycle the alkyl halide oxidatively adds to the Pd center with the generation of a Pd species (D). Reductive elimination followed by norbomene expulsion gives 2-alkyl-N-paUadaindole (F) which upon 1-protonation delivers the final 2-alkylated IH-indole product. 

The proposed catalytic cycle involves the transition of multiple oxidation states including Pd(0), (11), and (IV) (Scheme 3.22). Initial oxidative addition of Pd(0) to mono-ortho-substituted aryl iodide 82 leads to the Pd(II) intermediate 83. CarbopaUadation with norbomene 84 gives norbornylpalladium(II) 85. As syw- -hydride elimination is not possible, C-H activation at the ortho position takes place with the assistance of a base to generate the palladacycle 86. A second oxidative addition with an alkyl halide (R -X) leads to the Pd(IV) intermediate 87. Reductive elimination forms the ortho C-C bond and generates the norbornylpalladium(II)... 

Cycloolefin copolymer (COC) is an amorphous, clear metallocene product of norbomene and ethylene with a spectrum of attractive performance characteristics. Thus, COC (MFI at 190 °C and 2.16 kg = 1.7 dg min, p = 1,020 kg m ) was blended with C2+6 LLDPE (MFI at 190 °C and 2.16 kg = 3.2 dg min , p = 920 kg m ). The mechanical properties of the blends indicate immiscibility, despite the increased LLDPE crystallinity. The presence of COC improved the thermo-oxidative stability. Quasi-static tensile tests showed that increasing fraction of COC in the blends accounts for an enhancement of the elastic modulus and a decrease in the strain at break, while tensile strength passes through a minimum. A significant reduction of the creep compliance of LLDPE could be achieved only for the COC fractions exceeding 20 wt% (Dorigato et al. 2010). 

A British team [22] subjected the norbomene system (11a) to cleavage by reductive ozonolysis, affording the dialdehyde (12a) which has all the correct stereochemical features required in the prostaglandin. The dialdehyde (12a) was then converted by the sequence — reaction with methyl lithium, Jones oxidation and Baeyer—Villiger oxidation — to the diacetoxy compound (12b) and the latter, after debenzylation, subjected to an acetate rearrangement by refluxing in... 

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