Pinane-2-hydroperoxide

Commercially, autoxidation is used in the production of a-cumyl hydroperoxide, tert-huty hydroperoxide, -diisopropylbenzene monohydroperoxide, -diisopropylbenzene dihydroperoxide, -menthane hydroperoxide, pinane hydroperoxide, and ethylbenzene hydroperoxide. 

Another important use of a-pinene is the hydrogenation to i j -pinane (21). One use of the i j -pinane is based on oxidation to cis- and /n j -pinane hydroperoxide and their subsequent catalytic reduction to cis- and /n j -pinanol (22 and 23) in about an 80 20 ratio (53,54). Pyrolysis of the i j -pinanol is an important route to linalool overall the yield of linalool (3) from a-pinene is about 30%. Linalool can be readily isomerized to nerol and geraniol using an ortho vanadate catalyst (55). Because the isomerization is an equiUbrium process, use of borate esters in the process improves the yield of nerol and geraniol to as high as 90% (56). 

Another important process for linalool manufacture is the pyrolysis of i j -pinanol, which is produced from a-pinene. The a-pinene is hydrogenated to (73 -pinane, which is then oxidized to cis- and /n j -pinane hydroperoxide. Catalytic reduction of the hydroperoxides gives cis- and /n j -pinanol, which are then fractionally distilled subsequendy the i j -pinanol is thermally isomerized to linalool. Overall, the yield of linalool from a-pinene is estimated to be about 30%. 

In the case of diastereomeric mixtures of chiral hydroperoxides, standard chromatography on achiral phase can be employed to separate the diastereomers. As one example for the preparation of optically pure hydroperoxides via this method, the ex-chiral pool synthesis of the pinane hydroperoxides 11 is presented by Hamann and coworkers . From (15 )-cw-pinane [(15 )-cw-10], two optically active pinane-2-hydroperoxides cA-lla and trans-llb were obtained by autoxidation according to Scheme 17. Autoxidation of (IR)-c -pinane [(17 )-cw-10] led to the formation of the two enantiomers ent-lla and ent-llh. The ratio of cis to trans products was 4/1. The diastereomers could be separated by flash chromatography to give optically pure compounds. 

Synthesis from a-Pinene. a-Pinene from turpentine oil is selectively hydrogenated to cis-pinane [35], which is oxidized with oxygen in the presence of a radical initiator to give a mixture of ca. 75% cis- and 25% tran -pinane hydroperoxide. The mixture is reduced to the corresponding pinanols either with sodium bisulfite (NaHS03) or a catalyst. The pinanols can be separated by... 

The metal complexes, M +(acac)2 (M = Cu or Co), were observed to be bonded to the surface tether by a Schiff condensation reaction with the primary amine. The metal cations in these tethered complexes were used to activate t-butylhydroperoxide into radicals that reacted with the substrate, cis-pinane, to give mainly 2-pinane hydroperoxide with no observed formation of 2-pinanol. The selectivity to the pinane hydroperoxide was 93% for the immobilized Co(II) and 84% for the immobilized Cu(II) at 91 % substrate conversion. Blank reaction tests using the (1) oxidized carbon and (2) oxidized and hxd-functionalized carbon showed much lower activities ( 10-15% conversion) thus indicating that the tethered metal complexes were largely responsible for the observed activity. The subsequent reuse of the tethered catalysts eventually showed a constant activity ( 60% conversion) with reuse suggesting that the tethering method was effective in firmly attaching the metal ion to the surface. 

Cu, Co activated C Cu(acac)2, Co(acac)2 pinane + O2 -+2-pinane hydroperoxide 44... 

Metal-catalyzed oxidations with alkyl hydroperoxides a comparison between tert-hutyl hydroperoxide and pinane hydroperoxide... 

The oxidizing capacities of the bulky pinane hydroperoxide (PHP) and tert-butyl hydroperoxide (TBHP) were compared in oxidations catalyzed by Mo, V, Se, Os and Ru. 

In this present investigation we used pinane hydroperoxide (PHP) as a mechanistic probe to distinguish between peroxometal and oxometal pathways. In the peroxometal pathway the bulky pinane group is present in the active oxidant while in the oxometal pathway it is not. Hence, in the case of the peroxometal mechanism one might expect more steric constraints and consequently a slower reaction using the bulky PHP compared to the much less bulky TBHP [8]. In the case of oxometal mechanisms the difference between PHP and TBHP should be much smaller as the alkyl group is not present in the active oxidant. 

Acknowledgement We wish to thank the Netherlands Institute for Research on Catalysis (NIOK) for financial support and Quest International for supplying us with pinane hydroperoxide. 

The oxidation of cis-pinane by t-butyl hydroperoxide is catalysed by iron and cobalt phthalocyanines encapsulated in NaY zeohtes. The main reaction product is 2-pinane hydroperoxide which in turn decomposes giving substituted cyclobutanes. In contrast to the reaction in homogeneous phase, products of oxidation on C3 and C4 are not observed. 

Figure 1 - Products of auto-oxidation of pinane (1) pinane (2) 2-pinane hydroperoxide (3) 2-pinanol (4) pinocam-pheol (5) verbanol (6) pinocamphone (7) verbanone (8) a-terpineol, (9) 1-acetyl-2,2-dimethyl-3-ethylcyclobutane, (10) 2-(l-acetyl-2,2-dimethylcyclobut-3-yl)ethanol, (11) pinonic aldehyde, (12) pinonic acid.

The main product is pinane hydroperoxide (2) which can be reduced to 2-pinanol (3), an important intermediate in the industrial synthesis of linalool [1, 2, 3]. Pinocampheol (4), verbanol (5), pinocamphone (6) and verbanone (7) are also formed in minor amounts. When the reaction is carried out at temperatures higher than room temperature, pinane hydroperoxide is decomposed. It yields mainly the monocyclic products bearing the cyclobutyl ring (9 - 12) (Figure 1) [1], These products result from the fragmentation of the 2-pinanyloxy radicals which in turn result from the decomposition of 2-pinane hydroperoxide [1]. 

Pinane hydroperoxide is known to be completely converted to 2-pinanol by treatment with aqueous sodium sulfite [1]. The absence of 2-pinanol from the reaction mixture before that reductive treatment and its presence afterwards (Figure... 

Selectivity towards pinane hydroperoxide exhibits the highest values until higher conversions when the reaction is carried out in the presence of iron phthalocyanine encapsulated complexes (Figure 5). It even can be as high as 90% at a pinane conversion higher than 80%, when the reaction is carried out at 10 C For CoPc complexes the selectivity towards 2-pinane hydroperoxide exhibits an identical behaviour with the free and the encapsulated complex. 

Figure 5 - Selectivity to 2-pinane hydroperoxide for oxidation reactions carried out with free or encapsulated complexes. X - FePc - CoPc O - FePcNaY - CoPcNaY.

The selectivity for pinane hydroperoxide decreases when the reaction temperature increases (Table 4). Simultaneously, as the temperature increases more products resulting from the decomposition of pinane hydroperoxide are formed. 

The main product of the oxidation of cis-pinane with t-BHP over iron or cobalt phthalocy-anines encapsulated in Y zeolites (MPcNaY), at room temperature, is 2-pinane hydroperoxide. 

At higher temperatures pinane hydroperoxide decomposes yielding mainly 1-acetyl-2,2-dimethyl-3-ethylcyclobutane and 2-(l-acetyl-2,2-dimethylcyclobut-3-yl) ethanol. 

Materials. Styrene-Butadiene Rubber (SBR) Latex. SBR latex was prepared by redox emulsion polymerization using (in parts) butadiene (69) and styrene (31) at 6°-40°C (pinane hydroperoxide/sodium formaldehyde sulfoxylate/Fe++ as initiator) in the presence of potassium oleate (2.7) inorganic electrolytes (0.45) as polymerization aids, and demineralized water (135) until a conversion of 70% was achieved. Residual monomers were then removed. 

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