Organometallic enantiomeric scaffolding: general access to 2-substituted oxa- and azabicyclo[3.2.1]octenes via a Brønsted acid catalyzed [5 + 2] cycloaddition reaction.
6-Substituted TpMo(CO) 2(eta-2,3,4-pyranyl)- and TpMo(CO) 2(eta-2,3,4-pyridinyl) scaffolds (Tp = hydridotrispyrazolylborato) function as reaction partners in an efficient regio- and stereocontrolled synthesis of functionalized oxa- and azabicyclo[3.2.1]octenes through a novel Brønsted acid catalyzed [5 + 2] cycloaddition reaction. Excellent exo-selectivities are obtained, and the reaction gives products with complete retention of enantiomeric purity when carried out with chiral, nonracemic scaffolds. The substituent at C-6 of the eta (3)-coordinated heterocyclic scaffold not only influences [5 + 2] reactivity but also plays a critical role in the demetalation step directing the reaction to only one of two possible products.
Garnier
Ethel C
EC
Emory University, Department of Chemistry, 1515 Dickey Drive, Atlanta, Georgia 30322, USA.
Liebeskind
Lanny S
LS
D000143:Acids / Q000737:chemistry; D001372:Aza Compounds / Q000138:chemical synthesis*; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000138:chemical synthesis*; D034242:Cyclooctanes / Q000138:chemical synthesis*; D007769:Lactams / Q000138:chemical synthesis; D007783:Lactones / Q000138:chemical synthesis; D008982:Molybdenum / Q000737:chemistry; D009942:Organometallic Compounds / Q000737:chemistry; D011714:Pyrans / Q000737:chemistry; D011725:Pyridines / Q000737:chemistry; D013237:Stereoisomerism
D000143:Acids; D001372:Aza Compounds; D019086:Bridged Bicyclo Compounds, Heterocyclic; D034242:Cyclooctanes; D007769:Lactams; D007783:Lactones; D009942:Organometallic Compounds; D011714:Pyrans; D011725:Pyridines; D008982:Molybdenum