Studies on the Oxidation of cis- and trans-Pinane with molecular oxygen

Abstract

The pinanes are preferably attacked at the tertiary C‐H bond in 2‐position, but products of the oxidative attack at the secondary C‐H bonds in 3‐ and 4‐position are also found. At 100°C cis‐pinane is attacked more easily than trans‐pinane (kcis : ktrans = 6.4), the relative rates of attack at the secondary C‐H bonds in positions 3 and 4 with respect to the tertiary C‐H bond in 2‐position were also determined (in cis‐pinane ksec: ktert = 0.027; in trans‐pinane ksec : ktert = 0.20). After the attack at the 2‐C‐H bond the radical formed can either react with oxygen to form the corresponding cis‐ and trans‐peroxy radicals and further to give cis‐ and trans‐2‐hydroperoxy pinane or fragmentate to the monocyclic radical derived from α‐terpinene, giving as final products α‐terpinene hydroperoxide and the bicyclic 8‐hydroperoxy 4,4,8‐trimethyl 2,3‐dioxabicyclo[3.3.1]nonane. The corresponding alcohols were found after reduction with sodium sulphite. The oxidation at position 2 of the pinanes delivers not only the cis‐ and trans‐hydroperoxide but also, as shortlived intermediates, the corresponding 2‐pinanyloxy radicals. These radicals fragmentate forming a carbon radical with cyclobutane structure whose oxidation products were identified. Besides fragmentation of the 2‐pinanyloxy radical also an intramolecular H‐transfer from the methyl group in 9‐position to the oxygen of the trans‐2‐pinanyloxy radical takes place leading to 9‐hydroperoxy trans‐pinane‐2‐ol.

A Comparative Study of Solvent-Free and Highly Efficient Pinene Hydrogenation over Pd on Carbon, Alumina, and Silica Supports

“…Some natural hydrocarbons with specific architectures, including pinanes, are of great interest for the pharmaceutical, bio energy, fine chemistry, and flavor industry. − The low abundance of the natural cis - and trans -pinane isomers in essential oils obliges the industry to use a synthetic alternative: a metal catalytic hydrogenation of α or β-pinene, the major constituents of turpentine oil from most conifers, logically leads to the desired pinane products . However, the residual metal and solvent present at the end of the reaction represent an environmental and health concern.…”

Preparation of cis-pinane via α-pinene hydrogenation in water by using Ru nanoparticles immobilized in functionalized amphiphilic mesoporous silica

“…cis-Pinane is a kind of signicant industrial intermediate that is usually applied in medicine, materials and perfume owing to the high activity of its C 2 -H bond. [1][2][3][4] cis-Pinane is prepared by selective hydrogenation of a-pinene. Traditionally, a-pinene hydrogenation is commonly catalyzed by Pd/C 5 or Pt/C, 6 but the content of cis-pinane in products is very low.…”

Monoterpenoids

“…The catabolism of (+)-camphor (347) by Salvia oficinalis leads, inter alia, to its 6-hydroxy and 6-0x0 derivatives,38g and cells of the Acinetobacter sp. NCIB-9871 reduce racemic camphorquinone rac- (353) to a pair of diastereoisomeric exohydroxy ketones.390…”

“…(+)-Camphor (347) has been converted into the ally1 vinyl ether (366) which undergoes a [2,3]-Wittig rearrangement to yield a 70:30 mixture of (R)-( 367) and (S)- (368).398 The silyloxy aldehyde (369), derived from ( +)-camphor (347), undergoes acyloin rearrangement to give a mixture of the stable ketol (370) and the alternative ketol (371) which suffers facile aerial oxidation to yield homocamphoric anhydride.399 Anodic oxidation of (+)-camphor in acetonitrile with 1 mol dm-, H,SO, as the supporting electrolyte delivers the lactone (372) in up to 96 YO yield. This undergoes further electrochemical transformation in more strongly acidic media, yielding the butanolide (373).…”

“…of Ph,PCl then the salt (375) is formed, and this can be converted into the Pd and Pt complexes (376). When the nitroimines (377) are exposed to 60Co y-radiation they form radical anions which can be studied by ESR.,02 (+)-9-Bromocamphor (378) has been utilised as a chiral starting material in syntheses of the sponge metabolites (-)furodysin ( 379) and (-)-furodysinin (380).,03 The mechanism of the reaction of endo-3-bromocamphor (381) with N,Ndimethylaniline at 200 "C which gives camphor (347) has been investigated. 404 The same result can be achieved at much lower temperatures by using Et,Ndi-tert-butyl peroxide in acetonitrile.…”