Rhodium-catalyzed chemo-, regio-, and enantioselective [2 + 2 + 2] cycloaddition of alkynes with isocyanates.

[reaction: see text] We have developed a cationic rhodium(I)/modified-BINAP complex-catalyzed chemoselective [2 + 2 + 2] cycloaddition of alkynes with isocyanates leading to a wide range of 2-pyridones. This method was successfully applied to the chemo-, regio-, and enantioselective synthesis of axially chiral 2-pyridones from unsymmetrical alpha,omega-diynes, bearing an ortho-substituted phenyl at one terminal position, and alkyl isocyanates.