Features and applications of [Rh(CO)(2)Cl](2)-catalyzed alkylations of unsymmetrical allylic substrates.
A novel regio- and stereoselective [Rh(CO)2Cl]2-catalyzed allylic alkylation of unsymmetrical allylic carbonates was discovered. The regioselectivity of the reaction favors product ratios in which substitution occurs at the carbon bearing the leaving group. When an enantiomerically enriched carbonate (> or = 99% ee) was examined, the Rh(I)-catalyzed allylic alkylation proceeded stereoselectively to provide the alkylation product with retention of absolute stereochemistry (98% ee). To establish the scope of the [Rh(CO)2Cl]2-catalyzed allylic alkylation, a variety of carbon and heteroatom nucleophiles were examined and the results described. As an application of the Rh(I)-catalyzed allylic alkylation, a series of novel domino reactions have been developed that couple the unique regio- and stereoselective [Rh(CO)2Cl]2-catalyzed alkylation of allylic trifluoroacetates with an intramolecular Pauson-Khand annulation, a cycloisomerization, or a [5+2] cycloaddition. A unique aspect of the method described is the use of a single catalyst to effect sequential transformations in which the catalytic activity is moderated simply by controlling the reaction temperature. Implementation of such processes provides a rapid and efficient entry to a variety of bicyclic carbon skeletons from simple precursors.
Ashfeld
Brandon L
BL
Department of Chemistry and Biochemistry, The University of Texas, Austin, TX 78712, USA.
Miller
Kenneth A
KA
Smith
Anna J
AJ
Tran
Kristy
K
Martin
Stephen F
SF
D000478:Alkylation; D000498:Allyl Compounds / Q000737:chemistry*; D002244:Carbon / Q000737:chemistry; D002254:Carbonates / Q000737:chemistry; D002384:Catalysis; D008956:Models, Chemical; D012238:Rhodium / Q000737:chemistry*; D013237:Stereoisomerism; D013696:Temperature; D014269:Trifluoroacetic Acid / Q000737:chemistry
D000498:Allyl Compounds; D002254:Carbonates; D002244:Carbon; D012238:Rhodium; D014269:Trifluoroacetic Acid