Artemesia ketone

Allylation of acyloyl-imidazoles and pyrazoles61 with allyl halide mediated by indium in aqueous media provides a facile regioselective synthesis of P, y-unsaturated ketones (Scheme 11.1), which has been applied to the synthesis of the monoterpene artemesia ketone. The same product can be obtained by indium-mediated allylation of acyl cyanide (Eq. 11.35).62 Samarium, gallium, and bismuth can be used as a mediator for the allylation of nitrones and hydrazones to give homoallylic hydroxylamine and hydrazides in aqueous media in the presence of Bu4NBr (Scheme 11.2).63 The reaction with gallium and bismuth can be increased dramatically under microwave activation. 

Moreover, trapping of the carbene (159, R = pTol) by an allyl thioether leads largely to (160) removal of the protecting group provides a simple route to artemesia ketone (161) in 65% yield from (156, R = pTol) 126) ... 

Unexpected results have come to light bearing on monoterpenoid biosynthesis (Chapter 1). Banthorpe s group have shown that in the formation of the thujane and camphor skeletons, activity from labelled mevalonic acid can appear predominantly in the C5 unit supposedly derived from isopentenyl pyrophosphate and only to a minor extent in the dimethylallyl pyrophosphate-derived portion. Banthorpe has also presented evidence for a chrysanthemyl intermediate, analogous to presqualene alcohol, in the biosynthesis of artemesia ketone. 

Chrysanthemic acid (126), artemesia ketone (127), santolina triene (128) and lavandulol (129) are representatives of irregular monoterpenes which, unlike other regular monoterpenes, are not derived directly from geranyl pyrophosphate (59). By contrast to the regular... 

Ring cbsures through intramolecular alkylation of Reissert compounds have been described. The sequential dialkylation of dimethylaminoacetonitrile (44) first with methallyl chloride and then isopentenyl bromide, followed by hydrolysis and isomerization, affords artemesia ketone in 77% overdl yield (Scheme 20). ... 

Very few synthetic applications have appeared in this area, the most noteworthy being the extremely short synthesis of artemesia ketone (408) starting from the allyl sulfide (404 Scheme KW). If an al-kyne unit can replace a carbon-carbon double bond without apparent deleterious effect on the 3,2-rearrangement, so also can an allene unit. Dienes are then produced (Scheme lOS). ... 

Artemisia afra Willd. (African wormweed) The major components in A. afra oil (1.5%) from semi-dried leaves were 1,8-cineole (67%), terpinen-4-ol (7%) and bomeol (5%) (39). The oil from Zimbabwe contains mainly artemesia ketone (6.3-41.9%) and 1,8-cineole (0.1-27.9%) (40). In East Africa the aerial parts of A. afra are used to treat indigestion as well as sore throats and fever in children. The roots are used for treating intestinal worms and the leaves are chewed as emetic (35). In South Africa fumes from boiled leaves are inhaled for blocked nasal passages (41). 

Bates, R. B., and D. Feld Terpenoids. XIII. Conversion of Chrysanthemyl Alcohol to a Triene with the Artemesia Ketone Skeleton. Tetrahedron Letters 1967, 4875. 

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