Enantiopure cycloheptenones from (R)-(−)-carvone: intermediates for perhydroazulene terpenoids

Two routes for the synthesis of enantiopure cycloheptenones, intermediates for perhydroazulene terpenoids, have been developed. They feature totally regioselective Tiffeneau–Demjanov and Nozaki ring expansion reactions of (R)-(−)-carvone.

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(1R,5R)-5-Isopropenyl-2-methyl-1-trimethylsilanyloxy-cyclohex-2-enecarbonitrileC14H23NOSi[α]D25=-124 (c 2.9, CHCl3)Source of chirality: (R)-(−)-carvoneAbsolute configuration (1R,5R)

(1R,5R)-1-Aminomethyl-5-isopropenyl-2-methyl-cyclohex-2-enol-1C11H19NO[α]D25=-92.2 (c 2.0, CHCl3)Source of chirality: (R)-(−)-carvoneAbsolute configuration (1R,5R)

(R)-6-Isopropenyl-3-methyl-cyclohept-3-enoneC11H16O[α]D25=+30 (c 0.26, CHCl3)Source of chirality: (R)-(−)-carvoneAbsolute configuration (R)

(R)-6-Isopropenyl-3-methyl-cyclohept-2-enoneC11H16O[α]D25=+49.0 (c 0.13, CHCl3)Source of chirality: (R)-(−)-carvoneAbsolute configuration (R)

(1R,5R)-1-(dibromomethyl)-5-isopropenyl-2-methylcyclohex-2-enol-1C11H16Br2O[α]D25=-65.8 (c 1.5, CHCl3)Source of chirality: (R)-(−)-carvoneAbsolute configuration (1R,5R)

(1S,5R)-1-(Dibromomethyl)-5-isopropenyl-2-methylcyclohex-2-enol-1C11H16Br2O[α]D25=-20.4 (c 1.2, CHCl3)Source of chirality: (R)-(−)-carvoneAbsolute configuration (1S,5R)