Gold-catalyzed stereoselective reaction of tricarbonylchromium complexes of ortho-alkynyl benzaldehydes and benzaldimines with nucleophiles

Gold(I)-catalyzed reaction of ortho-alkynyl benzaldehyde tricarbonylchromium complexes with nucleophiles gave stereoselectively 1-anti- and syn-functionalized 1H-isochromene chromium complexes depending on the nature of nucleophile. By reaction with alcohols, 1-anti-alkoxy 1H-isochromene tricarbonylchromium complexes were obtained via gold benzopyrylium-type intermediates. On the other hand, carbon nucleophiles gave 1-syn-functionalized 1H-isochromene chromium complexes via stereoselective addition of nucleophiles to the activated carbonyl group and following cyclization. Methoxy group of 1-anti-methoxy-1H-isochromene chromium complex was substituted with carbon nucleophiles in the presence of Lewis acid to afford 1-anti-functionalized 1H-isochromene chromium complexes. These methods can be applied to the synthesis of enantiomerically pure trans- and cis-1,3-dimethylisochromans starting from a single planar chiral chromium complex. Similarly, ortho-alkynyl benzaldimine tricarbonylchromium complexes gave stereoselectively 1-syn- and anti-functionalized dihydroisoquinoline chromium complexes by gold(I)-catalyzed reaction with nucleophile.