Iron(II) catalyzed reductive radical cyclization reactions of bromoacetals in the presence of NaBH4: optimization studies and mechanistic insights
作者:Sara H. Kyne、Christophe Lévêque、Shiwen Zheng、Louis Fensterbank、Anny Jutand、Cyril Ollivier
DOI:10.1016/j.tet.2016.08.039
日期:2016.12
5-Exo-trig radical reductivecyclization reactions of bromoacetals are catalyzed by iron in the presence of the reducing agent NaBH4. Both iron(II) and iron(III) were found to effectively mediate these reactions. As shown by cyclic voltammetry, iron(III) can be reduced to an iron(II) precatalyst before passing through an identical reaction mechanism in which monoelectronic activation of the substrate
Copper-Catalyzed Dicarbofunctionalization of Unactivated Olefins by Tandem Cyclization/Cross-Coupling
作者:Surendra Thapa、Prakash Basnet、Ramesh Giri
DOI:10.1021/jacs.7b01922
日期:2017.4.26
We present a strategy that difunctionalizes unactivated olefins in 1,2-positions with two carbon-based entities. This method utilizes alkyl/arylzinc reagents derived from olefin-tethered alkyl/aryl halides that undergo radical cyclization to generate C(sp3)-Cu complexes in situ, which are intercepted with aryl and heteroaryl iodides. A variety of (arylmethyl)carbo- and heterocycles (N, O) can be synthesized
complexes such as FeCl2 and [FeCl2(dppe)2] (dppe=1,2‐bisdiphenylphosphinoethane) are efficient precatalysts for the radicalcyclization of unsaturated iodides and bromides in the presence of NaBH4 (see scheme). Cyclic voltammetry studies suggests that the reaction occurs through a radical mechanism via an anionic hydrido iron(I) species as the key intermediate for the activation of the substrates by electron
Tetrahydrofuran Derivatives from Epoxides <i>via</i> Group Transfer Cyclization or Reductive Radical Cyclization of Organotellurium and Organoselenium Intermediates
作者:Lars Engman、Vijay Gupta
DOI:10.1021/jo961578n
日期:1997.1.1
undergo grouptransfer cyclization to afford 2-substituted 4-[(aryltelluro)methyl]tetrahydrofurans (cis/trans = 1/3-1/10). The aryl beta-(prop-2-ynyloxy)alkyl tellurides similarly afforded 2-substituted 4-[(aryltelluro)methylene]tetrahydrofurans with an E/Z-ratio close to unity. The beta-(allyloxy)alkyl aryl selenides and aryl beta-(prop-2-ynyloxy)alkyl selenides failed to undergo grouptransfer cyclization
Elucidating Dramatic Ligand Effects on SET Processes: Iron Hydride versus Iron Borohydride Catalyzed Reductive Radical Cyclization of Unsaturated Organic Halides
作者:Sara H. Kyne、Martin Clémancey、Geneviève Blondin、Etienne Derat、Louis Fensterbank、Anny Jutand、Guillaume Lefèvre、Cyril Ollivier
DOI:10.1021/acs.organomet.7b00603
日期:2018.3.12
organic halides in the presence of NaBH4. Mechanistic investigations have established that the ligand bound to the metal center (acetonitrile versus ethylenebis(diphenylphosphine) (dppe)) plays a crucial role in the structure and reactivity of the active anionic iron(I) hydride ([HFeCl(dppe)2]−) and borohydride ([(η1-H3BH)FeCl(NCCH3)4]−) with unsaturated haloacetals. This work provides new insights