Chiral Ammonium Salt Catalyzed Asymmetric Alkylation of Unactivated Amides

Abstract

A chiral spirocyclic quaternary ammonium salt catalyzed asymmetric alkylation of unactivated amides under homogeneous conditions has been developed, giving the target products with up to 60% ee. This novel methodology provides a general and concise protocol for asymmetric α-functionalization of unactivated amides.

Chiral Quaternary Ammonium Salt‐Catalyzed Enantioselective Addition Reactions of Hydantoins

“…We started our investigations by optimizing the addition of the alanine‐based hydantoin 1a to acrylate 3a ( Table 1) using the chiral ammonium salts A−E ( Figure 1). [32–41] …”

“…We started our investigations by optimizing the addition of the alanine-based hydantoin 1a to acrylate 3a (Table 1) using the chiral ammonium salts AÀ E (Figure 1). [32][33][34][35][36][37][38][39][40][41] First experiments using Maruoka's catalyst A [37] and our bifunctional ammonium salt B [38] under classical phase-transfer conditions did not allow for any asymmetric induction (entries 1 and 2). Using the recently established spirobiindane-based ammonium salt C1 [39][40][41] resulted in low, but measurable, first levels of enantioselectivity (entry 3).…”

“…[32][33][34][35][36][37][38][39][40][41] First experiments using Maruoka's catalyst A [37] and our bifunctional ammonium salt B [38] under classical phase-transfer conditions did not allow for any asymmetric induction (entries 1 and 2). Using the recently established spirobiindane-based ammonium salt C1 [39][40][41] resulted in low, but measurable, first levels of enantioselectivity (entry 3). It should be emphasized that these reactions do not proceed in the absence of any ammonium salt catalysts, so these low levels of enantioselectivities can not be attributed to a non-catalyzed racemic background reaction, but to poor face-differentiation in the presence of the chiral catalysts.…”

Towards an Asymmetric β-Selective Addition of Azlactones to Allenoates

“…Testing the 3,4,5-trifluorobenzene-decorated catalyst B2 with K2CO3 in toluene next (entry 8) allowed for a slightly higher selectivity but still gave a relatively low yield only. Spirobiindane-based salts C emerged as promising alternative quaternary ammonium salt scaffolds recently [40,41] and were also the catalysts of choice in our recently developed -selective allenoate addition of isoxazolidinones 2 (compare with Scheme 1B [18]). Unfortunately, these catalysts were found to be lesssuited for our azlactone protocol, as exemplified for derivative C1 (entry 9).…”

Design a new unsymmetrical Schiff base chiral Co-complex containing ionic liquid groups as a reusable green catalyst in the epoxidation of alkenes

“…These catalysts have been shown to exhibit high activity and selectivity in alkene epoxidation reactions, with promising results in terms of yield and reusability. Moreover, their recyclability makes them economically viable and environmentally friendly, as their reuse helps reduce waste and lower the overall cost of the reaction [8, [23][24][25][26].…”