Rhodium-Catalyzed Olefin Isomerization/Enantioselective Intramolecular Alder-Ene Reaction Cascade

Abstract

The olefin isomerization/enantioselective intramolecular Alder-ene reaction cascade was achieved by using a cationic rhodium(I)/(R)-BINAP complex as a catalyst. A variety of substituted dihydrobenzofurans and dihydronaphthofurans were obtained from phenol- or naphthol-linked 1,7-enynes, respectively, with good yields and ee values.

The Palladium-Catalysed Intramolecular Alder-ene (IMAE) Reactions of Certain Heteroatom-Linked 1,6-Enynes: The Formation of Hexahydro-Indoles and -Benzofurans

“…[32] Rhodium(I)-based catalysts can also effect the IMAE reactions of heteroatom linked 1,6-enynes. [33][34][35][36][37][38] These can proceed in a highly enantioselective manner when appropriate chiral ligands are deployed. Zhang and co-workers have used such protocols in developing an elegant synthesis [34] of the butyrolactone-containing natural product (þ)-pilocarpine (25) (Chart 2).…”

“…Using protocols related to those detailed immediately above we have been able to complete a total synthesis of the racemic modifications of the crinine alkaloid hamayne (37) [41] and the structure assigned to the related natural product haemultine (38) (Chart 4). [42] In each instance the exocyclic olefin associated with the product of the relevant IMAE reaction was manipulated in order to introduce the C-ring hydroxyl group with the B-ring being established by subjecting a late-stage derivative of the product of the IMAE process to a Pictet-Spengler reaction.…”

Rhodium‐Catalyzed Intramolecular Cyclization of Naphthol‐ or Phenol‐Linked 1,6‐Enynes Through the Cleavage and Formation of sp2 CO Bonds

“…We recently reported an olefin isomerization/enantioselective intramolecular Alder‐ene reaction cascade of phenol‐ or naphthol‐linked 1,7‐enynes catalyzed by a cationic rhodium(I)/( R )‐binap complex (Scheme ) 9. This cascade reaction proceeds through the formation of phenol‐ or naphthol‐linked 1,6‐enynes, which possess an isobutenyl ether moiety, followed by rhodacycle formation and β‐hydride elimination 9.…”

“…We recently reported an olefin isomerization/enantioselective intramolecular Alder‐ene reaction cascade of phenol‐ or naphthol‐linked 1,7‐enynes catalyzed by a cationic rhodium(I)/( R )‐binap complex (Scheme ) 9. This cascade reaction proceeds through the formation of phenol‐ or naphthol‐linked 1,6‐enynes, which possess an isobutenyl ether moiety, followed by rhodacycle formation and β‐hydride elimination 9. We anticipated that phenol‐ or naphthol‐linked 1,6‐enynes possessing a vinyl ether moiety would react with the rhodium(I) complex to generate the corresponding rhodacycles, which would undergo β‐hydride or oxygen elimination (Scheme ) 10–12…”

Synthesis of a Library of Fluorescent 2‐Aryl‐3‐trifluoromethylnaphthofurans from Naphthols by Using a Sequential Pummerer‐Annulation/Cross‐Coupling Strategy and their Photophysical Properties

“…[3] Although naphthols are promising starting materials for constructing naphthofurans, the transformations usually require multistep procedures and are inherently inefficient. [4,5] Therefore, new, straightforward approaches to naphthofurans are desired.…”