Haibin Mao

Organocatalytic oxa/aza-Michael–Michael Cascade Strategy for the Construction of Spiro [Chroman/Tetrahydroquinoline-3,3′-oxindole] Scaffolds

A new useful and effective chiral amine-catalyzed oxa- and aza-Michael-Michael cascade methodology for the construction of enantiomerically enriched indolinones spiro-fused with chromans or tetrahydroquinolines is reported. By employing suitable organocatalysts depending on the different Michael donors (Ar-OH/Ar-NHR), the processes offered excellent stereocontrol (dr >20:1, >99% ee) under mild conditions.

Visible-light-induced direct C(sp3)–H difluromethylation of tetrahydroisoquinolines with the in situ generated difluoroenolates

An effective approach to C1-difluoromethylated tetrahydroisoquinoline derivatives has been developed through C-H functionalization of tertiary amines by visible-light photoredox catalysis. This method uses stable, easily obtained α,α-difluorinated gem-diol as the CF2 source. The corresponding products were obtained in moderate to high yields at ambient temperature.

Chiral Tertiary Amine Thiourea-Catalyzed Asymmetric Inverse-Electron-Demand Diels–Alder Reaction of Chromone Heterodienes Using 3-Vinylindoles as Dienophiles

A straightforward and efficient protocol for the construction of structurally and biologically interesting chiral flavanoids incorporating three privileged structures, i.e., chromanone, dihydropyran, and indole, has been developed on the basis of chiral bifunctional tertiary amine thiourea-catalyzed asymmetric inverse-electron-demand Diels-Alder reaction of chromone heterodienes and 3-vinylindoles, which were used as dienophiles.

Enantioselective Construction of Dihydropyran‐Fused Indoles through Chiral Calcium Phosphate Catalyzed Oxo‐Hetero‐Diels–Alder Reactions by Using 2‐Oxoindolin‐3‐ylidenes as Heterodienes

Carbon-carbon bond formation: A highly efficient method for the oxo-hetero-Diels-Alder reaction of 2-oxoindolin-3-ylidenes based on chiral calcium phosphate is described. In general, adducts were obtained with high yields and excellent diastereo- and enantioselectivities (up to 96 % yield, >99:1 endo/exo, >99 % ee; see scheme, Boc = tert-butoxycarbonyl).

Organocatalytic Asymmetric Michael-Type/Wittig Reaction of Phosphorus Ylides: Synthesis of Chiral α-Methylene-δ-Ketoesters

An asymmetric Michael-type reaction of phosphorus ylides and α,β-unsaturated ketones under the catalysis of a chiral ion pair catalyst has been described. The ion pair catalyst containing a chiral counteranion was prepared by simply mixing 9-amino-(9-deoxy)-epi-quinine with l-N-Boc-proline. The optically active α-methylene-δ-ketoesters could be obtained with good to excellent enantioselectivities (up to 95% ee) under mild reaction conditions.

Organocatalytic One‐Pot Synthesis of Highly Substituted Pyridazines from Morita–Baylis–Hillman Carbonates and Diazo Compounds

A biologically inspired organocatalytic one-pot synthesis of highly functionalized pyridazines, which are ubiquitous structural units in a number of biologically active compounds, has been developed by starting from readily available diazo compounds and Morita-Baylis-Hillman (MBH) carbonates. Under mild reaction conditions, this synthetic route tolerated significant substrate variation to deliver a broad range of substituted products, including CF3 -substituted pyridazines derivatives. Moreover, the introduction of trifluoromethyl groups into the ring of pyridazine could be completed conveniently from 2,2,2-trifluorodiazoethane.

Synthesis of Functionalized Isoquinolin-1(2H)-ones by Copper-Catalyzed α-Arylation of Ketones with 2-Halobenzamides

Copper is key: A concise route to isoquinolin-1(2H)-ones from simple and readily available starting materials is provided by an efficient copper-catalyzed annulation of ketones with 2-halobenzamides. The method is applicable to a wide range of ketones containing different functional groups furnishing the products in moderate to excellent yields.