Enantioselective Synthesis of Chromanones Bearing Quaternary Substituted Stereocenters Catalyzed by (1R)-Camphor-Derived N-Heterocyclic Carbenes

Abstract

A catalytic asymmetric intramolecular crossed-benzoin reaction for the synthesis of chromanones by novel camphor-derived N-heterocyclic carbenes is described. The corresponding chromanones bearing quaternary stereogenic centers were isolated in high yields with high to excellent enantioselectivity.

Recent Advances on Computational Investigations of N‐Heterocyclic Carbene Catalyzed Cycloaddition/Annulation Reactions: Mechanism and Origin of Selectivities

“…In 2016, Zhang et al. reported a DFT study on mechanism, regio‐ and stereoselectivities of NHC‐catalyzed intramolecular aldehyde‐ketone ( 67 ) crossed‐benzoin reaction, which involves a ring‐closure process after formation of the Breslow intermediate M128 (Scheme ) . All calculations were performed at the IEFPCM THF ‐M06‐2X‐D3/6–311++G(2df, 2pd)//IEFPCM THF ‐M06‐2X/6‐31G(d, p) level of theory.…”

NHC-Catalyzed Organocatalytic Asymmetric Approach to 2,2-Disubstituted Benzofuran-3(2H)-ones Containing Fully Substituted Quaternary Stereogenic Center

“…All other reagents were purchased from commercial suppliers. Catalysts A-O were prepared according to the known method [44][45][46][47]. Salicylaldehyde-derived substrates 1a-1p were prepared by using two-step procedure (Scheme 1).…”

“…Due to the ongoing interest in the development of chiral terpene-based N-heterocyclic carbene catalysts and their applications to organocatalytic reactions [44][45][46][47][48], we report the NHC-catalyzed stereoselective synthesis of functionalized 3-coumaranones and naphthofuranones via an intramolecular Stetter reaction. Due to the ongoing interest in the development of chiral terpene-based N-heterocyclic carbene catalysts and their applications to organocatalytic reactions [44][45][46][47][48], we report the NHC-catalyzed stereoselective synthesis of functionalized 3-coumaranones and naphthofuranones via an intramolecular Stetter reaction.…”

Recent Advances in Catalytic Asymmetric Synthesis of Tertiary Alcohols via Nucleophilic Addition to Ketones

“…In 2015, Rafiński's group designed a similar (1 R )‐camphor‐derived triazolium salt 142 , and found it to be highly efficient in the cross‐benzoin reaction of O‐tethered aldehyde‐ketone substrates 141 , providing an access to chromanones 144 in 81–99% yields and 44–96% ee s. Different from the report by You's group where NaOAc was used, Rafiński and co‐workers employed 2‐ tert ‐butylimino‐2‐diethylamino‐1,3‐dimethylperhydro‐1,3,2‐diazaphosphorine (BEMP, 15 mol%) as the base additive (Scheme ) . Shortly after, the same reaction was also reported by Ema et al.…”