Alkenes camphene

Various unsubstituted solid alkenes are able to quantitatively add gaseous halogenohydrides. Prominent examples are the cholesterol esters 128 that give stereospecifically the bromides 129 at -30 °C [75,75al and camphene (130) that gives stereospecifically the rearranged bromide 131 or the elusive camphene hydrochloride (132) with 100% yield [11] (Scheme 15). The quantitative solid-... 

While aqueous HF is unreactive towards alkene addition, anhydrous HF is surprisingly reactive. The addition of HF to simple alkenes, such as ethylene, propene and cyclohexene, has been effected by mixing the reagents in an appropriate metal container at temperatures of -78 to -45 °C, and gradually heating the mixture from room temperature to 90 C.7-9 Representative yields are 60-80%. Catalysts are unnecessary. Markovnikov addition is observed, but the stereochemistry of addition to norbomene is not clear.10 With bomylene11 and camphene,12 HF addition gives excellent yields of a mixture of products. 

Steric differences also explain the preferential binding of silver at the exocycUc alkene of limonene (49) . The binuclear reagents are effective at shifting the spectra of other terpenes with either an exocycUc double bond, such as S-pinene (50) and camphene (51), or an endocyclic double bond, such as a-pinene (52) and A-3-carene (53) . ... 

With cyclic alkenes, fairly high diastereoselectivity can be achieved. Hydrozirconation of norbomene, followed by TBHP oxidation, gives the exo-alcohol in 95% yield, while the more complex bicyclics camphene (37) and P-pinene (38) give the mixtures shown in equations (39) and (40), respectively. TTie hafnium analog shows the opposite preference with P-pinene and does not react with camphene at all, attributed to significantly greater steric demand. Diastereoselectivity in cyclohexanols obtained by hydrozirconation of ketones has also been examined. ... 

Acetates, benzoates, tosylates, and mesylates exhibit analogous [l,2,3]-eliminations upon (gas phase) pyrolysis. Thus, Patchouli-acetate (104) reacts to 105 and 106 (52%, and 46%, resp.)65) and 57 yields 107 (low conversion) with migration of phenyl40). In the pyrolysis of bomyl benzoate (108) mainly (54 %) camphene (109)66) is formed, the atisine-derivative 110 (a or P) yields stereospecifically 111 (ot-epimer, 90 %) or 112 (P-epimer, 95 %)67), and the adamantane mesylate (113) yields the alkene 114 (38 %)68). 

Alkenes (e.g. camphene) are readily prepared by the BF3,Et20-catalysed elimination of secondary borate esters.Terminal conjugated dienes may be prepared by Pd(OAc)2-PPh3-catalysed elimination from allyl phenyl ethers or allylic acetates [e.g. geranyl, neryl, and linalyl acetates to form similar mixtures of myrcene (60—74%), trans-ocimene (8—20%), and c -ocimene (14—20%)], and the complex [(i7-CsH5)Cr(NO)2]2 dehalogenates n/c-dihalides (e.g. limonene tetrabromide) without affecting other halides (except for benzyl halides). 

Formaldehyde can be coupled to an alkene in the presence of an acid to give a diol (152) or a 1,3-dioxane derivative (154) in what is known as the Prins reaction. l Allylic alcohols such as 153 can also be produced in this reaction. Camphene (155) reacted with formaldehyde and acid to give a 1 1 mixture of allylic alcohol 156 and the acetate 157, in 94% yield. Scandium tiiflate has been used to prepare tetrahydropyran-4-ol derivatives from aldehydes and homoallylic alcohols via a Prins-type cyclization. 3... 

Ester complexes formed in the absence of nitrogenous bases. Criegee s monoesters were formed by direct reaction of OSO4 with the alkene R (e.g. tetramethylethylene, cyclopentene, indene, camphene, cholesterol) and were easily isolated. He formulated them as presumably tetrahedral species (Figure 29a) i.e. as 0s02(02R)). Subsequent work showed them to be dimers, Os204(02R)2 (b), and the complex obtained from tetramethylethylene, 0s2 04(02C2Me4)2, was shown by X-ray... 

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