“…Based on the widespread interest in asymmetric trifluoromethylthiolation reactions [14,15] and our own recent experience in this field, [12a] we first focused on the asymmetric α‐trifluoromethylthiolation of 3‐cyano p‐methoxybenzyl‐(PMB)‐protected isoindolinone 1 a (Table 1) using different established, as well as newly designed, chiral ammonium salt catalysts A – D (Figure 1).…”
We herein report the ammonium saltcatalyzed synthesis of chiral 3,3-disubstituted isoindolinones bearing a heteroatom functionality in the 3-position. A broad variety of differently substituted CF 3 Sand RS-derivatives were obtained with often high enantioselectivities when using Maruoka's bifunctional chiral ammonium salt catalyst. In addition, a first proof-of-concept for the racemic synthesis of the analogous F-containing products was obtained as well, giving access to one of the rare examples of a fairly stable α-F-α-amino acid derivative.
“…Based on the widespread interest in asymmetric trifluoromethylthiolation reactions [14,15] and our own recent experience in this field, [12a] we first focused on the asymmetric α‐trifluoromethylthiolation of 3‐cyano p‐methoxybenzyl‐(PMB)‐protected isoindolinone 1 a (Table 1) using different established, as well as newly designed, chiral ammonium salt catalysts A – D (Figure 1).…”
We herein report the ammonium saltcatalyzed synthesis of chiral 3,3-disubstituted isoindolinones bearing a heteroatom functionality in the 3-position. A broad variety of differently substituted CF 3 Sand RS-derivatives were obtained with often high enantioselectivities when using Maruoka's bifunctional chiral ammonium salt catalyst. In addition, a first proof-of-concept for the racemic synthesis of the analogous F-containing products was obtained as well, giving access to one of the rare examples of a fairly stable α-F-α-amino acid derivative.
“…Unfortunately however, because of the unexpected pronounced sensitivity that we observed during all these test reactions, and despite the promising selectivities up to e.r . = 91:9, this reaction as such is far from being as robust and practical as other chiral ammonium salt catalyzed reactions that we investigated recently , , …”
Section: Resultsmentioning
confidence: 99%
“…Our group has a strong interest in asymmetric ion pairing catalysis and we recently reported that bifunctional ammonium salt catalysts containing a (thio)‐urea H‐bonding motive (i.e. catalysts A ) can be used for the asymmetric α‐hydroxylation of β‐keto esters 1 by using racemic oxaziridines 2 as the O‐transfer reagents (accompanied by a simultaneous resolution of the oxaziridines 2 as outlined in Scheme B) .…”
We herein report an ammonium salt‐catalyzed protocol for the regioselective ring opening of aryl‐aziridines with β‐keto esters. The reaction gives access to a variety of highly functionalized target molecules with two consecutive stereogenic centers and can be rendered enantioselective (up to e.r. = 91:9) by using bifunctional chiral ammonium salt catalysts.
“…In 2020, Waser and co-workers disclosed the synthesis of α-aryl-α-SCF 3 -β 2,2 -amino acids using an enantioselective, ammonium salt-catalysed α-trifluoromethylthiolation of isoxazolidin-5-ones ( Scheme 10 ) [ 44 ]. Starting from compound 30 , the use of catalyst 31 developed by Maruoka [ 45 ] along with CF 3 S-transfer reagent 32 allowed isolation of the quaternary substituted species 33d in excellent yield (90 %) with high enantioselectivity ( e.r .…”
“…Compound 33d could also be deployed directly in peptide synthesis through initial Boc deprotection followed by α-ketoacid-hydroxylamine (KAHA) ligation, affording dipeptide 36 in 70 % yield. Scheme 10 Synthesis of α-aryl-α-SCF 3 -β 2,2 -amino acids, Waser and co-workers [ 44 ]. …”
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