title: Gd(OTf)3-catalyzed synthesis of geranyl esters for the intramolecular radical cyclization of their epoxides mediated by titanocene(III).
abstract: A selective and mild method for the esterification of a variety of carboxylic acids with geraniol is developed. We demonstrated that the use of triphenylphosphine, I2, 2-methylimidazole or imidazole and a catalytic amount of Gd(OTf)3 resulted to be more active than the previous protocols, providing a 16-membered library of geranyl esters in higher yields and in shorter reaction times. The use of essential oil of palmarosa (Cymbopogon martinii), enriched with geraniol, as a raw material for the synthesis of the target compounds complemented and proved how sustainable and eco-friendly this protocol is. Finally, the selective 6,7-epoxidation of the obtained geranyl esters led us to study their regio-controlled radical cyclization mediated by titanocene(III) for the synthesis of novel (8-hydroxy-9,9-dimethyl-5-methylene cyclohexyl)methyl esters in moderate yields and with excellent stereoselectivities.
authors.affiliation: Laboratorio de Química Orgánica y Biomolecular, Universidad Industrial de Santander, Parque Tecnologico Guatiguara, Km 2 via refugio, Piedecuesta, A.A. 681011, Colombia. vkuznechnik@gmail.com kouznet@uis.edu.co.
authors.forename: William H
authors.initials: WH
authors.lastname: García Santos
authors.forename: Carlos E
authors.initials: CE
authors.lastname: Puerto Galvis
authors.forename: Vladimir V
authors.initials: VV
authors.lastname: Kouznetsov
mesh_terms: D002384:Catalysis; D060326:Chemistry Techniques, Synthetic; D056831:Coordination Complexes / Q000737:chemistry*; D003500:Cyclization; D004852:Epoxy Compounds / Q000737:chemistry*; D004952:Esters; D005609:Free Radicals / Q000737:chemistry; D005682:Gadolinium / Q000737:chemistry*; D008698:Mesylates / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D004852:Epoxy Compounds; D004952:Esters; D005609:Free Radicals; D008698:Mesylates; D009942:Organometallic Compounds; C406884:titanocene; D005682:Gadolinium