AbstractAn efficient synthesis of (E)‐5‐aryl(halo)methylenebicyclo[2.2.2]oct‐2‐enes is reported. Lewis acid‐promoted carbohalogenation of 4‐(3‐arylprop‐2‐ynyl)‐cyclohex‐2‐enols in dichloromethane proceeds rapidly to afford the exo‐methylene‐bridged bicycles in good yields. This method also provides an easy access to (E)‐5‐aryl(halo)methylenebicyclo[2.2.1]hept‐2‐enes from the five‐membered ring 2,6‐enynols. The reactions are procedurally simple and high yielding, producing the aryl(halo)methylene‐bridged bicycles in minutes under air and mild conditions.magnified image
Ring opening of cyclopropylketones induced by photochemical electron transfer
作者:Janine Cossy、Nathalie Furet、Samir BouzBouz
DOI:10.1016/0040-4020(95)00727-p
日期:1995.10
Depending on the substitution pattern of cyclopropylketones, the photochemically induced electron transfer of tertiary amines to cyclopropylketones leads either to the formation of 3-substituted cycloalkanones or to ring expanded products.
根据环丙基酮的取代方式,光化学诱导的叔胺电子转移至环丙基酮会导致3-取代的环烷酮的形成或环扩产物。
Experimental Studies on the Selective β-C–H Halogenation of Enones
Here we describe the realization of a one-pot protocol for the β-C–H halogenation of cyclic enones via umpolung of the β-carbon. The developed method includes hydrazone formation and selective β-halogenation (bromination, chlorination) with N-bromosuccinimide and Palau’chlor (2-chloro-1,3-bis(methoxycarbonyl)guanidine) followed by hydrolysis of the hydrazone moiety. Using the optimized conditions,
Photoinduced electron transfer (PET) reactions of α-cyclopropyl-substituted ketones and triethylamine (TEA) were used to initiate the cyclopropylcarbinyl-homoallyl rearrangement. The intramolecular cyclization reaction onto triple bonds was performed yielding bicyclic and spirocyclic compounds. Furthermore, in some preliminary studies it was shown that even intramolecular aromatic substitutions are
C−H Amination in Synthesis: An Approach to the Assembly of the B/C/D Ring System of Aconitine
作者:Rosemary M. Conrad、J. Du Bois
DOI:10.1021/ol702375r
日期:2007.12.1
A strategy for the preparation of aconitine is described that attempts to exploit chemoselective C-H amination and the electrophilic reactivity of oxathiazinane N,O-acetals for assembling the complex, polycyclic carbon framework of the natural product.
efficient gold‐catalyzed cyclization reactions of alkynyl silyl enol ethers were successfully applied to the preparation of bicyclo[3.2.1]octanone derivatives. Accordingly, after optimization of the gold catalytic system, several bicyclic α,β‐unsaturated keto adducts were synthesized in good to excellent yields. The process followed a major 5‐exo cyclization via an anti addition of the silyl enol ether to