Pinene, Wagner-Meerwein rearrangement with

Bomeol is oxidized to camphor with chromic or nitric acid dehydration with dilute acids yields camphene. Bomeol is readily esterified with acids, but on an industrial scale bornyl esters are prepared by other routes. For example, levorotatory bomeol is synthesized industrially from levorotatory pinenes by Wagner Meerwein rearrangement with dilute acid, followed by hydrolysis of the resulting esters [86]. 

Addition to bicycKc monoterpene olefins. The reagent reacts rcgiospeciiically with y-pinene (I) at —73° in ether to give the unstable 1 I adduct (2 -chlorosulfonyI-2,8,8-irimethyl-3-azatricyplo[5.l.l.0 ]nonane-4-one) in 65% yield. This adduct rearranges either thermally or on contact with silicic acid via a Wagner-Meerwein rearrangement to (3), yield 40 %. The adduct (2) is reduced by sodium sulfite to the /3-lactam (4 2.8,8-trimethyl-3-azatricyclo[5.l.l.O ]nonane-4-one) in 61 % yield. 

The enantioselective biomimetic total synthesis of the alkaloid (+)-aristotelone was accomplished by C.H. Heathcock and co-workers." The synthetic sequence commenced with a Hg(N03)2-mediated Ritter reaction between (1S)-(-)-P-pinene and 3-indolylacetonitrile. Upon protonation, the pinene underwent a Wagner-Meerwein rearrangement to generate a tertiary carbocation which reacted with the cyano group. The initially formed imine product was reduced to the corresponding amine by sodium borohydride in methanol. 

The acidic properties of HCofCO) may lead to rearrangement reactions prior to hydroformylation. Thus, treatment of optically pure a-pinene with syngas gave mainly 2-formyl-bornane (Scheme 1.17) [34]. The Wagner-Meerwein rearrangement can be rationalized by the effect of the acid. 

A BASF group showed that rhodium-catalyzed reaction of a-(-)-pinene gives (-l-)-3-formylpinane (Scheme 4.53) [11]. In contrast, the use of Co2(CO)g led to the formation of (-)-2-formylbornane. The Wagner-Meerwein rearrangement is mediated by the intermediarily formed HCo(CO)4 with acidic properties. Prior isomerization of a- to P-pinene can be avoided by applying a high CO partial pressure and low temperatures. Based on this protocol and a subsequent reductive amination, chiral aminomethyl-plnane was prepared in the 100 g scale. 

Hydroformylation of enantiomerically pure (—)-a-pinene with an unmodified Co catalyst gave mainly (—)-2-formyl-bornane (Scheme 6.8) [68]. The Wagner-Meerwein rearrangement is forced by the acidic properties of HCo(CO), which is formed from Co2(CO)g upon the effect of syngas. 

Manganese(m) acetate oxidation (cf. Vol. 3, p. 34) of camphene gives (186) as a 95 5 mixture by carboxymethyl radical insertion no rearranged products were obtained, in contrast to /3-pinene which gave Wagner-Meerwein products only, and no free-radical insertion.279 The E- and Z-isomers of (187) probably result from a non-concerted biradical intermediate formed by benzyne addition to camphene.280 Benzyl-lithium adds to the aminocamphor (188) exclusively from the exo-side whereas only the competing enolization reaction occurs with more sterically hindered organometallics.281... 

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