A highly enantioselective dearomative 3+2 cycloaddition of benzothiazole has been successfully developed. A wide range of benzothiazoles and cyclopropane‐1,1‐dicarboxylates are suitable substrates ...for this reaction. The desired hydropyrrolo2,1‐bthiazole compounds were obtained in excellent enantioselectivity and yields (up to 97 % ee and 97 % yield). With the same catalytic system, a highly efficient kinetic resolution of 2‐substituted cyclopropane‐1,1‐dicarboxylates was also realized.
A highly enantioselective dearomative 3+2 cycloaddition of benzothiazole has been successfully developed. A wide range of benzothiazoles and cyclopropane‐1,1‐dicarboxylates are suitable substrates for this reaction. The desired hydropyrrolo2,1‐bthiazole compounds were obtained in excellent enantioselectivity and yields. With the same catalytic system, a highly efficient kinetic resolution of 2‐substituted cyclopropane‐1,1‐dicarboxylates was also realized.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
A DMAP‐N‐oxide, featuring an α‐amino acid as the chiral source, was developed, synthesized and applied in asymmetric Steglich rearrangement. A series of O‐acylated azlactones afforded C‐acylated ...azlactones possessing a quaternary stereocenter in high yields (up to 97 % yield) and excellent enantioselectivities (up to 97 % ee). Compared to the widespread use of pyridine nitrogen, which serves as the nucleophilic site in the asymmetric acyl transfer reaction, we discovered that chiral DMAP‐N‐oxides, in which the oxygen now acts as the nucleophilic site, are efficient acyl transfer catalysts. Our finding might open a new door for the development of chiral DMAP‐N‐oxides for asymmetric acyl transfer reactions.
A DMAP‐N‐oxide, featuring an α‐amino acid as the chiral source, was developed, synthesized and applied in asymmetric Steglich rearrangement. A series of O‐acylated azlactones afforded C‐acylated azlactones possessing a quaternary stereocenter in high yields (up to 97 % yield) and excellent enantioselectivities (up to 97 % ee).
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The enantioselective synthesis of carbocyclic nucleosides through the palladium‐catalyzed asymmetric allylic amination of alicyclic Morita‐Baylis‐Hillman (MBH) adducts with purines was successfully ...developed. With a combination of Pd2(dba)3/L7 as catalyst, various optically active carbocyclic nucleosides featuring a C=C double bond in the carbocycle moiety were obtained in high yields (up to 97%) with excellent N9/N7‐selectivities (>95/5) and enantioselectivities (up to >99.6%). In addition, these nucleoside analogs allowed for rapid transformation to a variety of other interesting structurally diverse chiral carbocyclic nucleosides.
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A novel concept that conversion of chiral 2-substituted DMAP into its DMAP-N-oxide could significantly enhance the catalytic activity and still be used as an acyl transfer catalyst is presented. A ...new type of chiral 2-substituted DMAP-N-oxides, derived from l-prolinamides, has been rationally designed, facilely synthesized, and applied in the dynamic kinetic resolution of azlactones. Using simple MeOH as the nucleophile, various l-amino acid derivatives were produced in high yields (up to 98% yield) and enantioselectivities (up to 96% ee). Furthermore, α-deuterium labeled l-phenylalanine derivative was also obtained. Experiments and DFT calculations revealed that in 2-substituted DMAP-N-oxide, the oxygen atom acted as the nucleophilic site and the N–H bond functioned as the H-bond donor. High enantioselectivity of the reaction was governed by steric factors, and the addition of benzoic acid reduced the activation energy by participating in the construction of a H-bond bridge. The theoretical chemical study indicated that only when attack directions of the chiral catalyst were fully considered could the correct calculation results be obtained. This work paves the way for the utilization of the C2 position of the pyridine ring and the development of chiral 2-substituted DMAP-N-oxides as efficient acyl transfer catalysts.
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The phosphine-catalyzed asymmetric dearomative 3+2 cycloaddition of 2-nitrobenzofurans with aldehyde-derived Morita-Baylis-Hillman (MBH) carbonates or allenoate was developed. The reaction with MBH ...carbonates resulted in a series of cyclopentabenzofurans containing three contiguous stereocenters with good to high yields, diastereoselectivities and enantioselectivities. The use of allenoate also gave the target product with moderate enantioselectivity.
The phosphine-catalyzed asymmetric dearomative 3+2 cycloaddition of 2-nitrobenzofurans with aldehyde-derived MBH carbonates or allenoates was developed.
The enantioselective Friedel–Crafts alkylation reaction of β‐naphthols with donor–acceptor aminocyclopropane was developed. In the presence of a copper complex derived from Cu(OTf)2 and bisoxazoline, ...a series of γ‐substituted γ‐aminobutyric acid derivatives were obtained with good yields (up to 98 %) and excellent enantioselectivities (up to 98 %). Using this catalytic system, the 2‐amino cyclopropane‐1,1‐dicarboxylate was obtained with high enantiomeric excess (up to 98 %) by an efficient kinetic resolution (s values of up to 90). The Friedel–Crafts alkylation product could be transformed into a tetracyclic 1,3‐oxazine derivative.
The enantioselective Friedel–Crafts alkylation reaction of β‐naphthols with donor–acceptor aminocyclopropanes was developed for preparing chiral γ‐substituted aminobutyric acid derivatives. With this catalytic system, 2‐amino cyclopropane‐1,1‐dicarboxylate was obtained with high enantiomeric excess by an efficient kinetic resolution. The Friedel–Crafts alkylation product could be transformed into a tetracyclic 1,3‐oxazine derivative.
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Intermolecular asymmetric dearomative 1,3-dipolar cycloaddition of 2-nitrobenzofurans with azomethine ylides was enabled by using a chiral Cu(i)/(S,Sp)-iPr-Phosferrox catalyst. As a result, a series ...of highly stereoselective chiral 2,3-fused hydrobenzofurans possessing four contiguous stereogenic centers were obtained with good to high yields, diastereoselectivities and enantioselectivities. The reaction has broad substrate scope tolerating various functional groups.
The Yb(OTf)
3
-catalyzed 3+2 cycloaddition of donor-acceptor cyclopropanes with thiourea offers an efficient route to diverse 2-amino-4,5-dihydrothiophenes (up to 92% yield), in which optically ...active 2-amino-dihydrothiophenes can be produced from enantiomerically pure cyclopropanes. Thiourea, which is an odorless and cheap reagent, provides a C&z.dbd;S double bond, serves as an amino source, and functions as a decarbalkoxylation reagent in this reaction. Preliminary mechanistic studies demonstrate that the reaction undergoes a sequential 3+2 cycloaddition/deamination/decarboxylation process.
The Yb(OTf)
3
catalyzed 3+2 cycloaddition of donor-acceptor cyclopropanes with thiourea offers an efficient route to diverse 2-amino-4,5-dihydrothiophenes.
A highly regioselective Minisci reaction with the decarboxylative alkylation of purine nucleosides under mild conditions was developed. With 5 mol % AgNO3 as a catalyst and (NH4)2S2O8 as an oxidant, ...a series of purine nucleosides including ribosyl, deoxyribosyl, arabinosyl purine nucleosides worked well with primary, secondary, and tertiary aliphatic carboxylic acids.
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An electrosynthetic approach was developed for the oxidative C-H/N-H cross-coupling amination of cyclic sulfamidate imines under undivided electrolytic conditions
via
an atom- and step-economic ...method. In this transformation, a wide variety of cyclic or acyclic dialkyl amines, amino acid derivatives, and more challenging primary anilines acted as suitable substrates with good reaction outcomes. The synthetic advantage of this electrochemical method is augmented by high functional group compatibility (86 examples), ease of scale-up to gram scale, and accomplishment of late-stage functionalization of complex biologically relevant molecules, which provides an efficient tool with broad potential application prospects in medicinal and synthesis chemistry. Mechanistic studies reveal that this transformation probably occurred through a radical process.
An efficient and eco-friendly electrochemical synthesis of various cyclic
N
-sulfonylamidines from cyclic sulfamidate imines and amines
via
oxidative C-H/N-H cross-coupling under mild reaction conditions has been developed.
