SELECTIVE O-METHYLOXIME FORMATION FROM CLOPENTYL)-METHYL]-3,4-DIHYDRONAPHTHALEN-1(2H)-ONE

Reaction of yclopentyl)methyl]-3,4-dihydronaphthalen-1(2H)-one (4a) wi th 1 or 2 moles of O-methylhydroxylamine hydrochloride in pyridine gav e yclopentyl)methyl]-3,4-dihydronaphthalen-1(2H)-one (E)-2'-O-methylox ime (5a), or the corresponding 2',5'-bis(O-methyloxime) (6), respectiv ely. A minor product from the formation of the bis(O-methyloxime) (6) was the (Z) isomer (5b) of the mono(O-methyloxime) (5a); the structure and stereochemistry of (5a) and (5b) were established by X-ray crysta llography. Reduction of the keto bis(O-methyloxime) (6) with 0.25 mole of lithium aluminium hydride gave a diastereomeric mixture of the cor responding alcohols (7a), of which the major isomer was characterized by ester formation. The bis(O-methyloxime) (6) could be hydrolysed to the parent triketone (4a), but it resisted deprotection with cetyltrim ethylammonium permanganate. Reaction of the triketone (4a) with 1 mole of 4-anisidine in the presence of 4-toluenesulfonic acid resulted in retro Michael cleavage with formation of '-methoxyphenyl)amino-2-methy lcyclopent-2-en-1-one (1).