[2+2+2] Cycloaddition reaction with the participation of unsaturated ketones catalyzed by an Rh(i)—Sn(ii) system

Codimerization of vinyl ketones with metallylacetone or metallylacetophenone in the presence of [RhCl(C₂H₄)₂]₂-SnCl₂ affords substitutedendo-2-acyl-8-oxabicyclo[3.2.1]octanes, the products of the formal [2+2+2] cycloaddition.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2280–2283, November, 1995.We thank Uve Ihhoff (Moscow Representative of Bruker GmbH) for the provision of their AMX 400 spectrometer.     

Intermolecular gold-catalyzed diastereo- and enantioselective [2+2+3] cycloadditions of 1,6-enynes with nitrones

Going for gold: The title reaction has been developed and demonstrates a wide substrate scope with respect to the 1,6-enynes and nitrones (see scheme; DCE = 1,2-dichloroethane, Tf = trifluoromethanesulfonyl). The results for the enantioselective versions are also presented.     

Highly enantioselective spiro cyclization of 1,6-enynes catalyzed by cationic skewphos rhodium(I) complex

A cationic rhodium(I) complex having a skewphos ligand is shown to be a highly enantioselective catalyst for asymmetric carbocyclization of 1,6-enynes with tri-substituted olefins to control quaternary stereogenic centers of spiro-rings.     

Asymmetric Synthesis of a Fused Tricyclic Hydronaphthofuran Scaffold by Desymmetric [2+2+2] Cycloaddition

A rhodium(I)‐BINAP‐catalyzed highly enantioselective [2+2+2] cycloaddition of enynes with alkynes has been developed. Diverse fused tricyclic hydronaphthofuran scaffolds with three consecutive stereogenic centers were constructed in one step from easily available materials with excellent chemo‐, regio‐, diastereo‐, and enantioselectivity. Notable features of these reactions include 100 % atom economy, very broad scope, and mild reaction conditions.     

Rhodium‐Catalyzed [3+2+2] and [2+2+2] Cycloadditions of Two Alkynes with Cyclopropylideneacetamides

It has been established that a cationic rhodium(I)/H₈‐binap complex catalyzes the [3+2+2] cycloaddition of 1,6‐diynes with cyclopropylideneacetamides to produce cycloheptadiene derivatives through cleavage of cyclopropane rings. In contrast, a cationic rhodium(I)/(S)‐binap complex catalyzes the enantioselective [2+2+2] cycloaddition of terminal alkynes, acetylenedicarboxylates, and cyclopropylideneacetamides to produce spiro‐cyclohexadiene derivatives which retain the cyclopropane rings.