Synthesis Samarium Barbier reaction

Sml2, which can be prepared conveniently from samarium powder and 1,2-diiodoethane in THF, finds application as a versatile one-electron reducing agent in organic synthesis. Two typical synthetic procedures mediated by Sml2 are the pinacol coupling of aldehydes and the Barbier reaction, as shown in the following schemes ... 

Molander, G. A., McKie, J. A. A facile synthesis of bicyclo[m.n.1]alkan-1-ols. Evidence for organosamarium intermediates in the samarium(ll) iodide promoted intramolecular Barbier-type reaction. J. Org. Chem. 1991,56,4112-4120. 

Molander, G. A., Le Huerou, Y., Brown, G. A. Sequenced Reactions with Samarium(ll) Iodide. Sequential Intramolecular Barbier Cyclization/Grob Fragmentation for the Synthesis of Medium-Sized Carbocycles. J. Org. Chem. 2001,66,4511-4516. 

A cydization/Barbier-type reaction was reported by Curran and coworkers [21] in 2004 in the total synthesis of penitrem D 46. In this work, the aryl radical generated from the iodoarene 41 and Smij proceeded to attack the tethered cyclobutene to from a cyclobutyl radical 42. Subsequently, reaction with Smij led the organo-samarium species 43, which underwent a Barbier-typie reaction with acetone to give the tertiary alcohol 44 in 40% yield. The product contains the BCD ring system of penitrem D 46 (Scheme 5.12). 

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