Brønsted acid-catalyzed enantioselective addition of 1,3-diones to in situ generated N-acyl ketimines.

A Brønsted acid-catalyzed asymmetric Mannich-type addition of 1,3-diones to cyclic N-acyl ketimines is reported for the synthesis of enantioenriched isoindolinones. Various dicarbonyl-substituted isoindolinones bearing a quaternary carbon stereocenter were synthesized with excellent yields (up to 98%) and moderate to high enantioselectivities (up to 95% ee), and most of them possess a fluorine atom at the reactive center. Furthermore, the synthetic utility of the protocol has been demonstrated by the debenzoylation of the product.

Organocatalytic Asymmetric Cascade Michael-acyl Transfer Reaction between 2-Fluoro-1,3-diketones and Unsaturated Thiazolones: Access to Fluorinated 4-Acyloxy Thiazoles.

Quinine derived bifunctional urea catalyzed cascade Michael-acyl transfer reaction of 5-alkenyl thiazolones and monofluorinated ß-diketones has been developed. The fluorine containing 4-acyloxy thiazoles were synthesized in high yields and good diastereo-and excellent enantioselectivities. Synthetic transformations, including synthesis of 4-hydroxy thiazoles, have been demonstrated.

Cu(I)-Catalyzed asymmetric exo-selective synthesis of substituted pyrrolidines via a 1,3-dipolar cycloaddition reaction.

An (R)-DM-BINAP/Cu(CH3CN)4BF4 complex catalyzed exo-selective asymmetric 1,3-dipolar cycloaddition (1,3-DCA) reaction of imino esters with α,ß-unsaturated pyrazoleamides has been developed. A series of highly functionalized pyrrolidines with multiple stereogenic centers were obtained with good yields and diastereoselectivities and excellent enantioselectivities (up to 99% ee).

A General Catalytic Route to Enantioenriched Isoindolinones and Phthalides: Application in the Synthesis of ( S)-PD 172938.

Chiral Brønsted acid catalyzed enantioselective syntheses of isoindolinones and phthalides have been accomplished via tandem Mannich-lactamization and aldol-lactonization reactions, respectively. A variety of enantioenriched isoindolinones (up to 99% ee) and phthalides (up to 85% ee) containing α-diazoesters were afforded in excellent yields. Furthermore, a concise synthesis of ( S)-PD 172938 has been demonstrated by using this protocol.

A chiral Brønsted acid-catalyzed highly enantioselective Mannich-type reaction of α-diazo esters with in situ generated N-acyl ketimines.

A chiral phosphoric acid-catalyzed asymmetric Mannich-type reaction of α-diazo esters with in situ generated N-acyl ketimines, derived from 3-hydroxyisoindolinones has been demonstrated in this communication. A variety of isoindolinone-based α-amino diazo esters bearing a quaternary stereogenic center were afforded in high yields (up to 99%) with excellent enantioselectivities (up to 99% ee). Furthermore, the synthetic utility of the products has been depicted by the hydrogenation of the diazo moiety of adducts.

(R)-DM-SEGPHOS-Ag(I)-Catalyzed Enantioselective Synthesis of Pyrrolidines and Pyrrolizidines via (1,3)- and Double (1,3)-Dipolar Cycloaddition Reactions.

An efficient diastereo- and enantioselective route to access a wide range of highly substituted pyrrolidine and pyrrolizidine derivatives has been described via (1,3)- and double (1,3)-dipolar cycloaddition reactions catalyzed by the (R)-DM-SEGPHOS-Ag(I) complex. The reactions proceed smoothly at ambient temperature, affording a variety of pyrrolidines and pyrrolizidines in high yields (up to 93%) with up to 99:1 dr and excellent enantioselectivities (up to 98% ee) without any additives. The newly synthesized pyrrolidine and pyrrolizidine derivatives contain four and seven contiguous stereogenic centers, respectively. Moreover, the synthetic utility of enantioenriched products has been demonstrated by transforming them into various synthetically useful advanced intermediates.

Asymmetric direct vinylogous Michael addition to 2-enoylpyridine N-oxides catalyzed by bifunctional thio-urea.

Catalytic enantioselective direct vinylogous Michael addition of α,α-dicyanoalkenes to 2-enoylpyridine N-oxides with a bifunctional organocatalyst is described. The methodology offers an efficient way to install an asymmetric carbon-carbon bond at the γ-position of α,α-dicyanoalkenes in excellent regio-, diastereo-, and enantioselectivity. Further, application in desymmetrization of achiral α,α-dicyanoalkene to access highly functionalized enantioenriched cyclohexylidenemalononitrile derivatives has been demonstrated.

Enantioselective Mukaiyama-Michael with 2-enoyl pyridine N-oxides catalyzed by PYBOX-DIPH-Zn(II)-complexes at ambient temperature.

A chiral PYBOX-DIPH-Zn(II) catalyzed enantioselective Mukaiyama-Michael reaction of acyclic silyl enol ethers with 2-enoylpyridine N-oxides has been studied in external additive free conditions at ambient temperature. The methodology offers straightforward access to a variety of functionalized chiral 1,5-dicarbonyl compounds, which could easily be elaborated into synthetically viable pyrones via hydrolysis followed by cyclization. A transition state model has been proposed to explain the stereochemical outcome.

Enantioselective synthesis of 3,4-dihydropyran derivatives via a Michael addition reaction catalysed by chiral pybox-diph-Zn(II) complex.

An enantioselective Michael addition of cyclic 1,3-dicarbonyls to 2-enoylpyridine N-oxides catalyzed by a chiral pybox-diph-Zn(II) complex has been developed. The corresponding Michael adducts have been obtained in high yields with up to >99% ee. The Michael adduct has been transformed to biologically active 2,4-disubstituted hexahydroquinoline. A plausible transition-state model has been proposed to explain the stereochemical outcome of the reaction.

Enantioselective synthesis of coumarin derivatives by PYBOX-DIPH-Zn(II) complex catalyzed Michael reaction.

A potential pharmacologically active chiral 3-substituted 4-hydroxy-2-oxo-2H-chromene skeleton has been synthesized by enantioselective Michael addition catalyzed by PYBOX-DIPH-Zn(OTf)(2) complex. The methodology has successfully been employed in the synthesis of (R)-Warfarin and another related compounds.

Enantioselective Michael addition of malonates to 2-enoylpyridine N-oxides catalyzed by chiral bisoxazoline-Zn(II) complex.

An enantioselective Michael addition of malonates to 2-enoylpyridine N-oxides catalyzed by a chiral bisoxazoline-Zn(II) complex has been developed. The corresponding Michael adducts have been obtained in high yields with up to 96% ee. A plausible transition-state model has been proposed to explain the stereochemical outcome of the reaction.