Chiral synthesis of 6,7-benzomorphans: Synthesis of (−)1( S),2( S),4( R),6( R)-1,2,3,4,5,6-hexahydro-2,6-methano-8-methoxy -1,3,4,6-tetramethyl-3-benzazocine through the chromium hexacarbonyl mediated cyclisation of 1( S),1′( R)-1,2-dihydro-7-methoxy-1,4-dimethyl -1( N-methyl- N-trifluoroacetamido-1′-methylethan-2′-yl)naphthalene

Abstract

(−)1( S),2( S),4( R),6( R)-1,2,3,4,5,6-Hexahydro-2,6-methano-8-methoxy- 1,3,4,6-tetramethyl-3-benzazocine has been synthesised in 86 % enandomeric excess from the α-(ν 6-chromium tricarbonyl) complex of 1( S),1′( R)-1,2-dihydro-7-methoxy-1,4-dimethyl-1-( N-methyl- N-trifluoroacetamido-1′-methylethan-2′-yl)naphthalene. A precursor of this compound is 2( R),4( S)-4-(3-methoxyphenyl)-2,4-dimethylcyclohexanone which was obtained through an Enders' type C-methylation reaction of 4-(3-methoxyphenyl)4-methylcyclohexanone using SAMP as the reagent.