title: Mild TiIII- and Mn/ZrIV-catalytic reductive coupling of allylic halides: efficient synthesis of symmetric terpenes.
abstract: Two new efficient methods for the regioselective homocoupling of allylic halides using either catalytic TiIII or the combination Mn/ZrIV catalyst have been developed. The regio- and stereoselectivity of the process proved to increase significantly when the Mn/ZrIV catalyst is used as the coupling reagent and when cyclic substituted allylic halides are used as substrates. The use of Lewis acids such as collidine hydrochloride allowed the quantity of catalyst to be lowered up to 0.05 equiv. We have proved the utility of these protocols with the synthesis of different terpenoids such as (+)-beta-onoceradiene (1), (+)-beta-onocerine (2), squalene (5), and advanced key-intermediates in the syntheses of (+)-cymbodiacetal (3) and dimeric ent-kauranoids as xindongnin M (4a).
authors: Department of Organic Chemistry, Institute of Biotechnology, University of Granada, Avda. Fuentenueva, 18071 Granada, Spain. afbarre@goliat.ugr.es
authors: Alejandro F
authors: AF
authors: Barrero
authors: M Mar
authors: MM
authors: Herrador
authors: José F Quílez
authors: JF
authors: del Moral
authors: Pilar
authors: P
authors: Arteaga
authors: Jesús F
authors: JF
authors: Arteaga
authors: Horacio R
authors: HR
authors: Diéguez
authors: Elena M
authors: EM
authors: Sánchez
mesh_terms: D002384:Catalysis; D045786:Diterpenes, Kaurane / Q000138:chemical synthesis / Q000737:chemistry; D006846:Hydrocarbons, Halogenated / Q000138:chemical synthesis / Q000737:chemistry; D008345:Manganese / Q000737:chemistry*; D039821:Monoterpenes; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry; D013185:Squalene / Q000031:analogs & derivatives / Q000138:chemical synthesis / Q000737:chemistry; D013729:Terpenes / Q000138:chemical synthesis* / Q000737:chemistry; D014025:Titanium / Q000737:chemistry*; D014315:Triterpenes / Q000138:chemical synthesis / Q000737:chemistry; D015040:Zirconium / Q000737:chemistry*
chemical_list: D045786:Diterpenes, Kaurane; D006846:Hydrocarbons, Halogenated; D039821:Monoterpenes; D009942:Organometallic Compounds; D013729:Terpenes; D014315:Triterpenes; C486259:cymbodiacetal; D008345:Manganese; D013185:Squalene; D015040:Zirconium; D014025:Titanium; C019556:squalane