Mild TiIII- and Mn/ZrIV-catalytic reductive coupling of allylic halides: efficient synthesis of symmetric terpenes.
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).
Barrero
Alejandro F
AF
Department of Organic Chemistry, Institute of Biotechnology, University of Granada, Avda. Fuentenueva, 18071 Granada, Spain. afbarre@goliat.ugr.es
Herrador
M Mar
MM
del Moral
José F Quílez
JF
Arteaga
Pilar
P
Arteaga
Jesús F
JF
Diéguez
Horacio R
HR
Sánchez
Elena M
EM
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*
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