Optimized iminium-catalysed 1,4-reductions inside the resorcinarene capsule: achieving >90% ee with proline as catalyst

Abstract

A supramolecular container enables highly enantioselective iminium chemistry using simple proline as the chiral source.

Catalytic Asymmetric Conjugate Reduction

“…More recently, a supramolecular approach for enantioselective catalysis in confined spaces was also reported by Tiefenbacher and co-workers using the self-assembled hexamer of the resorcinarene unit 75. [135] Here, [(75) 6 • -(H 2 O) 8 ] behaved as a molecular reactor, where the reduction could be accomplished by L-proline OC6 as the aminocatalyst (Figure 30). Interestingly, ee values much higher than those observed with OC6 alone were observed, suggesting a possible strong supramolecular influence.…”

Supramolecular catalysis in confined space: making the pyrogallol[4]arene capsule catalytically active in non-competitive solvent

“…Differently, when an equimolar mixture of CP 6 / 3 was reacted (in 1 : 1 ratio, Table 1, entry 6), the formation of singly-occupied capsules 3@CP 6 and I@CP 6 , that are catalytically inactive, was predominant. 39 Thus, in the presence of the pyrogallol[4]arene capsule CP 6 , and switching from competitive chloroform to non-competitive benzene as the reaction solvent, we observe an inversion of endo / exo diastereoselectivity for the 1,3-DC in Scheme 1.…”

Catalytic Asymmetric Conjugate Reduction

“…More recently, a supramolecular approach for enantioselective catalysis in confined spaces was also reported by Tiefenbacher and co‐workers using the self‐assembled hexamer of the resorcinarene unit 75 [135] . Here, [( 75 ) 6 ⋅(H 2 O) 8 ] behaved as a molecular reactor, where the reduction could be accomplished by L‐proline OC6 as the aminocatalyst (Figure 30).…”

“…hexamer of the resorcinarene unit 75. [135] Here, [(75) 6 • -(H 2 O) 8 ] behaved as a molecular reactor, where the reduction could be accomplished by L-proline OC6 as the aminocatalyst (Figure 30). Interestingly, ee values much higher than those observed with OC6 alone were observed, suggesting a possible strong supramolecular influence.…”