Gold(I)-Catalyzed Highly Diastereo- and Enantioselective Constructions of Bicyclo[3.2.1]oct-6-ene Frameworks via (4 + 3)-Cycloadditions

A one-pot
construction of bicyclo[3.2.1]­oct-6-ene frameworks involves
gold-catalyzed (4 + 3)-cycloadditions between 2-(1-alkynyl)-2-alken-1-ones
and substituted cyclopentadienes; diastereoselectivity (dr >25:1)
and enantioselectivity (up to 99.9% ee) are achieved with a chiral
gold catalyst. Our DFT calculations suggest a three-step ionic mechanism
for the cycloadditions of gold-containing 1,3-dipoles with cyclopentadienes,
in which an exo-spatial arrangement is preferable.

双环[3.2.1]辛-6-烯骨架的一锅法合成，涉及金催化的2-(1-炔基)-2-烯-1-酮类化合物与取代环戊二烯类化合物之间的(4+3)环加成反应；采用手性金催化剂可实现非对映选择性（非对映选择性比值dr >25:1）与对映选择性（最高达99.9%的对映体过量值ee）。本研究通过密度泛函理论（DFT）计算表明，含金1,3-偶极体与环戊二烯类化合物的环加成反应遵循三步离子机理，其中外型空间排布为优势构型。