Enantioselective Redox‐Divergent Chiral Phosphoric Acid Catalyzed Quinone Diels–Alder Reactions

Abstract

An efficient enantioselective construction of tetrahydronaphthalene-1,4-diones as well as dihydronaphthalene-1,4-diols by a chiral phosphoric acid catalyzed quinone Diels-Alder reaction with dienecarbamates is reported. The nature of the protecting group on the diene is key to the success of achieving high enantioselectivity. The divergent "redox" selectivity is controlled by using an adequate amount of quinones. Reversible redox switching without erosion of enantioselectivity was possible from individual redox isomers.

Chiral Phosphoric Acid‐Catalyzed Enantioselective Formal [4+2] Cycloaddition Between Dienecarbamates and 2‐Benzothioazolimines

“…As such, Bernardi et al reported the use of simple unsubstituted dienecarbamates [12] in Povarov reaction leading to the synthesis of 1,2,3,4-tetrahydroquinolines (Scheme 1b, right). [13] In continuation of our research program in catalytic asymmetric reactions with dienecarbamates, [14] we decided to explore their reactivities in connection with 2-benzothiazolimines. Indeed, these imines are versatile synthetic intermediates used for the syntheses of various heterocycles [15] and they have been embedded in direct catalytic asymmetric annulation strategies.…”

Enamides and dienamides in phosphoric acid-catalysed enantioselective cycloadditions for the synthesis of chiral amines

“…Following our work on the asymmetric (3 + 2) cycloaddition between enecarbamates and quinones, 76 we found that thiodienecarbamates could effectively react with quinones in an enantioselective (4 + 2)-cycloaddition with (S)-SPINOL (S)-5b as chiral phosphoric acid catalyst. 77 Interestingly, a divergent synthesis of redox isomers, dihydronaphthalene-1,4-diols 75 and tetrahydronaphthalene-1,4-diones 76, 75b,78 was controlled by adequate amount of the quinones employed. The enantioselectivity was found to be highly dependent on the protecting group of the diene.…”

Regiodivergent Organocatalytic Reactions

“…In general, binaphthyl is used to synthesize chiral phosphoric acid derivatives. These catalysts have been involved in several reactions including the Diels-Alder, Nazarov, Mukaiyama Aldol, Mannich, Henry, Morita-Baylis-Hillman reactions, and 1,3-dipolar cycloadditions [146][147][148][149][150][151][152][153][154].…”