Visible-light-induced organocatalytic enantioselective N–H insertion of α-diazoesters enabled by indirect free carbene capture

Abstract

While asymmetric insertion of metal carbenes into H−X (X = C, N, O, etc.) bond has been well-established, asymmetric control over free carbenes is challenging due to the presence of...

Visible-Light-Induced Synthesis of 3-Alkyl Chromones under Catalyst- and Additive-Free Conditions

“…When radical scavenger 2,2,6,6–tetramethylpiperidine1-oxyl (TEMPO) was added to the reaction system, product 3a was obtained in a 47% yield (Scheme , eq 1). Furthermore, HRMS analysis of the reaction mixture detected the TEMPO adduct 6 , providing evidence for the formation of the triplet carbene during this reaction. , Then, by adding 1,1–diphenylethylene (DPE) to the reaction, the yield was slightly inhibited (Scheme , eq 2), investigating whether this protocol might not involve a radical process. In addition, we speculated that ketone 5 would be the reaction intermediate, which was detected by HRMS analysis and easily formed from diazo compound oxidized by oxygen .…”

Enantioselective organocatalytic strategies to access noncanonical α-amino acids

“…The reaction employs CPA 74 as the catalyst for the N-H insertion of anilines. 183 While Li and Zhou tackled the challenging reactivity of free carbenes by modulating the catalyst to perfectly t the substrates, Guo and Sun adopted the strategy to lower the reactivity of the carbene by trapping it with a suitable additive, DMSO (Scheme 70). The result is a sulfoxonium ylide, which can undergo a formal enantioselective insertion reaction under the catalysis of CPA 74.…”

Application of sulfonium and sulfoxonium ylides in organocatalyzed asymmetric reaction

“…Although that catalytic asymmetric insertion reaction of metal carbenes into N-H bond with the enantioselective control via metal-chiral metal interaction has been well-established [74,75] , the asymmetric insertion reaction of free carbenes into N-H bond faces a challenge due to strong background reactions and lack of any anchor for a catalyst interaction. Recently, Guo et al made progress in the catalytic enantioselective insertion reaction of free carbenes into N-H bond using an indirect approach [76] .…”