Enantio- and Diastereoselective Carbonyl-Ene Cyclization–Acetalization Tandem Reaction Catalyzed by Tris(pentafluorophenyl)borane-Assisted Chiral Phosphoric Acids

Abstract

Highly enantio-and diastereoselective carbonyl-ene cyclization was developed with the use of chiral Lewis acid-assisted chiral Brønsted acid (LBA) catalysts, which were prepared in situ from both sterically demanding tris(pentafluorophenyl)borane and chiral phosphoric acids. Along with the performance of standard carbonyl-ene cyclizations, carbonyl-ene cyclization− acetalization tandem reactions with the use of additional aldehydes were demonstrated with high enantio-and diastereoselectivities. On the basis of mechanistic examinations, a stepwise reaction pathway via tertiary carbocation intermediates involving possible transition states is proposed.

Multiselective Diels–Alder Reaction of α-Arylacroleins Catalyzed by Boron Tribromide-Assisted Chiral Phosphoric Acids

“…In this regard, we have already developed acid–base cooperative B­(C 6 F 5 ) 3 -assisted chiral Lewis acid catalysts for multiselective Diels–Alder (DA) reactions, in which the enantio-, endo/exo -, π-facial, regio-, site-, and substrate-selectivity can be controlled successfully . Moreover, we have also developed acid–base cooperative BBr 3 - or B­(C 6 F 5 ) 3 -assisted chiral phosphoric acid ( 1 ) catalysts for multiselective carbon–carbon-bond-forming reactions (Figure ), , such as DA reactions of 1,2-dihydropyridines, [2 + 2]-cycloaddition reactions between phenyl vinyl sulfide and acroleins, hetero Diels–Alder (HDA) reactions of α,β-substituted acroleins with ethyl vinyl sulfide, and carbonyl-ene cyclization–acetalization tandem reactions…”

“…The common positive nonlinear effect in endo - 4e , exo - 4e , and endo - 5e might exclude unexpected individual behavior in each reaction due to different active species. Although it would be feasible to assume an equilibrium between the monomer and dimer of ( R )- 1a , based on our previous study on BX 3 -( R )- 1 catalysts, the active species in the present reaction might adopt a monomeric structure as shown in Figure . Therefore, we conducted computational calculations on the complex of BBr 3 , ( R )- 1a , and 3e in the model reaction (Figure ; for details, see the Supporting Information).…”

An overview of the applications of chiral phosphoric acid organocatalysts in enantioselective additions to CO and CN bonds

“…These fluorinated catalysts allow avoiding the use of additional Lewis acids, as it has been reported for similar transformations in which the sole use of a chiral phosphoric acid gives unsatisfactory results. 261,262…”

“…These fluorinated catalysts allow avoiding the use of additional Lewis acids, as it has been reported for similar transformations in which the sole use of a chiral phosphoric acid gives unsatisfactory results. 261,262 The addition of 3-vinyl indoles 320 to in situ generated N-Boc aldimines catalysed by BINOL-derived phosphoric acid (R)-BPA1 was reported by Guo and co-workers (Scheme 99). 263 The reaction tolerates the presence of both, aromatic and aliphatic aldehydes 86, as well as several EDG and EWG substituents in the indole and aromatic moieties of the vinyl indoles, providing a wide scope of chiral N-Boc amines 321 in high yields and enantiocontrol (62-98%, 78-97%).…”

Enantioselective access to tricyclic tetrahydropyran derivatives by a remote hydrogen bonding mediated intramolecular IEDHDA reaction

“… 22 , for examples on neutral alkene-participated asymmetric reactions see ref. 25 ) 22 – 31 , and the difficulty to find a suitable catalyst being able to efficiently “chelate” the simple α,β-unsaturated ketone or aldehyde electrophile in order to achieve a high facial selectivity. In the synthetic approaches presented above, β,γ-unsaturated ketoesters, unsaturated oxazolidinones and acyl imidazoles were employed to efficiently complex with the metal catalyst (see Fig.…”