ACYLATION-CYCLOALKYLATION - NEW ANNELATION ROUTE TO EUDESMANES

Condensation of vinylacetyl chloride (3) with 9-chloro-l-p-menthene (1) followed by distillation and chromatography gave 4H-7-(2'-chloro-l'-methylethyl)-4a, 5, 6, 7, 8, 8a-hexahydro-4a-methyl-l-naphthalenone (4) (38% yield) and 2R-7-(2'-chloro-l'-methylethyl)-3, 4, 5, 6, 7, 8-hexahydro-4-methyl-l-naphthalenone (9) (33% yield). Catalytic hydrogenation of 4, followed by ketalization, elimination of hydrogen chloride with potassium tert-butoxide in Me2SO, and hydrolysis afforded 7-isopropenyl-4a-methyloctahydro-l-naphthalenone (16). Condensation of 16 with methylenetriphenylphosphorane afforded (+)-β-selinene (17) while reaction with methylmagnesium iodide yielded neointermedeol (18). The structure of ketone 9 was shown by conversion to occidol (22). © 1979, American Chemical Society. All rights reserved.