Ring opening of α-pinene epoxide

Isomerization of β-pinene oxide over Sn-modified zeolites

“…The catalyst showed very high activity albeit poor selectivity values for either myrtanal, myrtenol or perillyl alcohol, while selectivity to other products amounted to 67% [13]. Another homogeneous catalyst, p-toluenesulfonic acid gave 17% yield of myrtanal together with 10% myrtenol, 9% perillylaldehyde and 8% perillyl alcohol [18]. Alternatively myrtanal was prepared in one pot via oxidation of ␤-pinene with a homogeneous catalyst Mn(III)SalenCl·H 2 O giving a maximum conversion of 30% and 54% selectivity towards myrtanal [19].…”

A study of some molecularly imprinted polymers as protic catalysts for the isomerisation of α-pinene oxide to trans-carveol

“…The identification of a good transition-state analogue for the transformation of a-pinene oxide 6 into 5 was far from obvious. The mechanisms are still under debate, 15 but carbonium ion 7 is generally accepted to be the preliminary intermediate. Although formation of this carbocation should be the rate-determining step, the selectivity of the transformation is determined during the subsequent collapse of this reactive intermediate 7 since most of the products derive from this common species.…”

10.1007/s11178-008-1001-3

“…In the presence of InCl 3 , 85% of aldehyde 28 is selectively formed [39]. Treatment of α-pinene epoxide 26 with p-toluenesulfonic acid provides aldehyde 28 [40]. The yield of 28 in the isomerization of 26 over SiO 2 -Al 2 O 3 (Si/Al 70) or SiO 2 -ZrO 2 under mild conditions (5 min at room temperature) attained 72%, though some by-products were also formed [41]; among the latter, pinocamphone (30) and aldehyde 29 were identified.…”