An efficient procedure for the preparation of (E)-alpha-alkylidenecycloalkanones mediated by a CeCl(3) x 7H(2)O-NaI system. Novel methodology for the synthesis of (S)-(-)-pulegone.
2-Alkylidenecycloalkanones are powerful synthons used as the key intermediates in many important syntheses. Because of their potential, a general method of preparation from readily available starting materials, under very mild conditions, was considered to be worthwhile. Cerium(III) chloride heptahydrate in combination with sodium iodide in refluxing acetonitrile promotes a regio- and stereoselective beta-elimination reaction to (E)-2-alkylidenecycloalkanones in 2-(1-hydroxyalkyl)cycloalkanones. The synthetic value of the present procedure is demonstrated by the synthesis of monoterpene (S)-(-)-pulegone (8) in its optically active form.
Bartoli
Giuseppe
G
Department of Chemical Sciences, University of Camerino, via S. Agostino 1, I-62032 Camerino (MC), Italy.
Bosco
Marcella
M
Dalpozzo
Renato
R
Giuliani
Arianna
A
Marcantoni
Enrico
E
Mecozzi
Tiziana
T
Sambri
Letizia
L
Torregiani
Elisabetta
E
D000473:Alkanes / Q000138:chemical synthesis*; D002384:Catalysis; D002625:Chemistry, Organic / Q000379:methods*; D000081005:Cyclohexane Monoterpenes; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D039821:Monoterpenes / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
D000473:Alkanes; D000081005:Cyclohexane Monoterpenes; D039821:Monoterpenes; C039648:pulegone