Chinese Journal of Chemistry

The cover picture shows the first catalytic asymmetric Morita-Baylis-Hillman (MBH) reaction of acrolein with aromatic aldehydes. Simplicity is beauty. As one of the simplest nucleophiles in MBH reaction, acrolein has never been used for the catalytic asymmetric reaction with aldehydes, although the resulting MBH adducts, with a versatile aldehyde group, are extremely useful. The Hatakeyama's catalyst β-isocupreidine, in combination with 20 mol% of 2,6-dimethoxybenzoic acid, is found to be able to catalyze the reaction of acrolein with aromatic aldehydes to give the desired MBH adducts in up to 81% ee. More details are discussed in the article by Zhou et al. on page 2631–2635.

A new set of reaction conditions has been established and allowed for the first non-noble Cu(II)-catalyzed asymmetric 1,4-hydrosilylation of N-aryl β-enamino esters under air to afford a selection of N-aryl β-amino acid esters in moderate-to-good enantiopurities (ee up to 91%).

In the presence of 5 mol% of chiral N-triflyl phosphoramide 1a, various pyrrolo-[1,2-a]indoles were obtained in excellent enantioselectivity, moderate yields and up to 3:1 diastereoselectivity through the one-pot synthesis including the Friedel-Crafts alkylation reaction of 4,7-dihydroindole with β,γ-unsaturated α-keto esters and the subsequent p-benzoquinone oxidation.

The direct cross aldol reactios between aldehydes and ketones were investigated with modularly designed organocatalysts (MDOs). Primary α-amino acids were found to be better reaction-center modules in this reaction.

We report the first example of catalytic asymmetric Morita-Baylis-Hillman reaction of acrolein with aromatic aldehydes. The use of 10 mol% of Hatakeyama's catalyst β-isocupreidine C4, in combination with 20 mol% of 2,6-dimethoxybenzoic acid, could catalyze the reaction to give the desired products in up to 81% ee.

A concise method was developed to prepare α-monofluorinated-β-amino through N-sulfinyl urea catalyzed asymmetric hydrosilylation of α-fluoro-β-enamino esters, which affords highly yields, good to high diastereoselectivities (up to >99/1) and moderate to good enantioselectivities (up to 83% ee).

A planarly chiral ligand/palladium-catalyzed asymmetric allylic amination of Morita-Baylis-Hillman acetates with simple aromatic amines was developed in good yield with excellent α-regioselectivity (α:γ up to 30:1) and moderate enantioselectivity (up to 70% ee).

An iridium-catalyzed allylic substitution of unsymmetrical allyl carbonates with sodium phenyl selenide was accomplished, which produced the linear allyl phenyl selenides in 38%–74% yields. The asymmetric iridium-catalyzed allylations of sodium phenyl selenide were presented as well.

Chiral phosphinothiourea derived from D-glucose was developed as efficient organocatalyst for the enantioselective Morita-Baylis-Hillman reaction between acrylates and aldehydes.

The enantioselective hydrogenation of benzils was developed by using the cationic Ru(OTf)(TsDPEN)(η⁶-cymene) complex as catalyst, which provided a series of enantiomerically enriched hydrobenzoins derivatives in up to 96% yield, 87:13 diastereoselectivity and >99% enantioselectivity.

Unsymmetrical hybrid phosphine-aminophosphine ligand derived from 1,2,3,4-tetra-hydro-1-naphthylamine has been found to be highly efficient in the Ir-catalyzed asymmetric hydrogenation of various 2H-1,4-benzoxazines, providing good enantioselectivities (up to 95% ee) and high catalytic activity (S/C up to 5000).

Binaphthyl sulfonimides have been developed to catalyze the asymmetric Michael addition of ketone to alkylidene malonates, affording the corresponging products in good to high yields (up to 98%) with good to excellent diastereoselectivity (up to 99:1 dr) and enantioselectivity (up to 92% ee) under mild conditions in water.

An efficient asymmetric domino reaction of amino aldehyde to β,γ-unsaturated α-keto esters was achieved by using trans-perhydroindolic acid 1d as a chiral organocatalyst with excellent asymmetric behavior. Under the optimal reaction conditions, products with more than 99% de and up to 93% ee were obtained in high chemical yield (up to 98%) for a series of β,γ-unsaturated α-keto esters. The methodology provided an efficient route to dihydropyran derivatives containing many substituent groups (including amino groups).

Chiral terminal 1,2-diols were successfully prepared in good yields with high enantiopurities by a process of cinchona alkaloids-catalyzed formal [3+2] cyclization of acyl chlorides and oxaziridine, followed by reduction.

An organocatalytic asymmetric branching sequence was realized in the presence of 10 mol% of (DHQD)₂AQN, affording the sequential products with three stereocentres, including two quaternary carbon centres, in 47%–79% yields with 85%–99% ee.

The enantioselective double Michael reaction of benzofuranone with dienones catalyzed by Cinchona-based primary amines was developed. A wide range of optically active spirocyclic benzofuranones were obtained in good yields (up to 89%) and enantioselectivities (up to 91% ee).

A chiral C₂-symmetric pyrrolidine-based tetraamine was synthesized from commercially starting materials, which showed good catalytic activity for asymmetric Michael additions of ketones to nitroalkenes and chalcones. The reactions proceeded smoothly to give the corresponding products in good yields (up to 99% and 91%) and in a highly selective manner (up to 91% and 93% ee) under mild conditions.

Asymmetric 1,3-dipolar cycloaddition of methyl α-fluoroacrylate with azomethine ylides for the construction of optically active fluorinated pyrrolidines bearing one unique fluorinated quaternary and two tertiary stereogenic centers has been achieved with Cu(CH₃CN)₄BF₄/TF-BiphamPhos complexes for the first time. This catalytic system performs well over a broad scope of substrates, providing the synthetically useful adducts in high yields and excellent diastereoselectivities and good to high enantioselectivities.

The highly enantioselective cross-dehydrogenative coupling of aldehydes with benzylic compounds has been developed as an efficient and rapid protocol for synthesis of enantioriched α-alkylated aldehydes.