Additions to bicyclic olefins. III. Stereochemistry of the epoxidation of norbornene, 7,7-dimethylnorbornene, and related bicyclic olefins. Steric effects in the 7,7-dimethylnorbornyl system

Abstract

A systematic study of the stereochemistry of epoxidation of norbornene, 7,7-dimethylnorbornene, and related bicyclic olefins was undertaken in order to establish more precisely the importance of steric effects in controlling the direction of concerted additions to such systems. The epoxidation of norbornene proceeds almost exclusively exo, 99%, whereas the corresponding epoxidation of 7,7-dimethylnorbornene takes place preferentially from the opposite direction, 88-94% endo. 1 -Methylnorbornene, 2-methylnorbornene, and 1,7,7-trimethylnorbornene exhibit the same steric pattern of reaction. Similarly, epoxidation of the exocyclic double bond in 2-methy-

Electrodeposition of Copper Oxide Nanoparticles on Precasted Carbon Nanoparticles Film for Electrochemical Investigation of anti‐HIV Drug Nevirapine

“…For the purpose of showing the synthetic potential of our compounds, epoxidation of the CC bond of 1,2,3,4,5,6‐hexahydrobenzo[ f ]isoquinoline derivative 5 o was realized with 3‐chloroperoxybenzoic acid as oxidant (Scheme ) 15…”

Bicyclofulvene, IX. Stereoelektronische Effekte bei der Addition an 8‐Methylentricyclo[3.2.0 2,4 ]octan‐Derivate

“…Zur Darstellung von 8 wollten wir ein geeignetes NorbornenDerivat von der endo-Seite her epoxidieren. Dazu mu13 der giinstigere exo-Angriff durch einen 7-syn-standigen Substituenten abgeschirmt werden 17). Wir hofften deswegen, da13 die Reaktionsfolge von 11 iiber 12 zu 8 fiihren konnte.…”

m-Chloroperbenzoic Acid

“…18 Due to steric and other factors, the norbornene (11) undergoes selective (99%) epoxidation from the exo face. 19 In 7,7-dimethylnorbornene (12), approach to the exo face is effectively blocked by the methyl substituent at C-7, and (12) is epoxidized from the unfavored endo face, although much more slowly (1% of the rate of epoxidation of 11). 19 The geminal methyl group at C-7 is able to block the approach of the peroxy acid even when the double bond is exocyclic to the norbornane ring system (for example, epoxidation of (13) proceeds with 86% exo attack, while (14) is oxidized with 84% endo attack).…”

“…19 In 7,7-dimethylnorbornene (12), approach to the exo face is effectively blocked by the methyl substituent at C-7, and (12) is epoxidized from the unfavored endo face, although much more slowly (1% of the rate of epoxidation of 11). 19 The geminal methyl group at C-7 is able to block the approach of the peroxy acid even when the double bond is exocyclic to the norbornane ring system (for example, epoxidation of (13) proceeds with 86% exo attack, while (14) is oxidized with 84% endo attack). Folded molecules are epoxidized selectively from the less hindered convex side; m-CPBA epoxidation of the triene lactone (15) takes place from the α-face with 97% stereoselectivity.…”

“…Henbest showed that in the absence of severe steric interference, allylic cyclohexenols are epoxidized stereoselectively by organic peroxy acids to furnish cis-epoxy alcohols; 24a a large number of cis-epoxy alcohols have been prepared by epoxidizing allylic cyclohexenols. 7 A mixture (5:1) of labile bisallylic alcohols (19) and (20) was reacted with m-CPBA (eq 5); from the reaction mixture diepoxide (21) was isolated as a single isomer. 25 Epoxidation of (Z)-cyclooct-2-en-1-ol (22) Stereoselectivity has been observed during the peroxy acid epoxidation of some homoallylic and bishomoallylic alcohols, 28 and the epoxidation of the allylic carbamate (24) is syn stereoselective (eq 7).…”