Facile synthesis of 1,4-oxazines by ruthenium-catalyzed tandem N-H insertion/cyclization of α-arylamino ketones and diazo pyruvates.

Herein, we report an efficient strategy for the rapid construction of 1,4-oxazines starting from simple α-amino ketones and diazo pyruvates under mild reaction conditions. This transformation is efficiently catalyzed by RuCl3 through a tandem N-H insertion/cyclization sequence via an enol formation. This reaction shows broad functional group tolerance, and the resulting 1,4-oxazine products show promising anticancer activities toward HCT116.

Brønsted Acid Catalyzed Enantioselective Assembly of Spirochroman-3,3-oxindoles.

An enantioselective cyclization of diazoindolinones with o-hydroxymethyl chalcones has been established by a cooperative dirhodium complex and chiral phosphonic acid catalysis under mild conditions. This reaction is the first example of catalytic asymmetric intramolecular Michael-type trapping of oxonium ylide enabled by phosphoric acid through a dual H-bonding activation model, which provides an efficient access to the chiral spirochroman-3,3-oxindoles, with vicinal quaternary and tertiary stereocenters, in good to excellent yields and enantioselectivities.

Catalytic asymmetric synthesis of 2,5-dihydrofurans using synergistic bifunctional Ag catalysis.

We report a bifunctional Ag catalyst promoted intramolecular capture of oxonium ylides with alkynes for the enantioselective synthesis of 2,5-dihydrofurans. This represents unprecedented synergistic catalysis of a bifunctional Ag catalyst. Mechanistic studies revealed that [(R)-3,5-DM-BINAP](AgSbF6)2 (9) is likely to be the active catalytic species and that the reaction involves second order kinetics with respect to 9, suggesting that two molecules of 9 are involved in the intramolecular trapping of a Ag-associated oxonium ylide with a Ag-activated alkyne. Based on our mechanistic hypothesis, we further optimized the reaction, rendering a facile approach to 2,5-dihydrofurans in good to excellent yields in a highly chemo- and enantioselective fashion.

Cu(I)-Catalyzed Three-Component Reaction of α-Diazo Amide with Terminal Alkyne and Isatin Ketimine via Electrophilic Trapping of Active Alkynoate-Copper Intermediate.

A three-component reaction between terminal alkyne, α-diazo amide, and isatin ketimine is realized by utilizing copper catalysis. A series of alkynyl-containing 3,3-disubstituted oxindoles were synthesized with high efficiency and diastereoselectivity under mild reaction conditions. This transformation is proposed to proceed through a Mannich-type trapping of an alkynoate copper intermediate derived from terminal alkyne and copper carbene species.

1,2,3,4-Tetrahydroisoquinolines as inhibitors of HIV-1 integrase and human LEDGF/p75 interaction.

Alkaloids are a class of organic compounds with a wide range of biological properties, including anti-HIV activity. The 1,2,3,4-tetrahydroisoquinoline is a ubiquitous structural motif of many alkaloids. Using a short and an efficient route for synthesis, a series of 1,2,3,4-tetrahydroisoquinolines/isoquinolines was developed. These compounds have been analysed for their ability to inhibit an important interaction between HIV-1 integrase enzyme (IN) and human LEDGF/p75 protein (p75) which assists in the viral integration into the active genes. A lead compound 6d is found to inhibit the LEDGF/p75-IN interaction in vitro with an IC50 of ~10 µm. Molecular docking analysis of the isoquinoline 6d reveals its interactions with the LEDGF/p75-binding residues of IN. Based on an order of addition experiment, the binding of 6d or LEDGF/p75 to IN is shown to be mutually exclusive. Also, the activity of 6d in vitro is found to be unaffected by the presence of a non-specific DNA. As reported earlier for the inhibitors of LEDGF/p75-IN interaction, 6d exhibits a potent inhibition of both the early and late stages of HIV-1 replication. Compound 6d differing from the known inhibitors in the chemical moieties and interactions with CCD could potentially be explored further for developing small molecule inhibitors of LEDGF/p75-IN interaction having a higher potency.

Metal-Free Domino One-Pot Decarboxylative Cyclization of Cinnamic Acid Esters: Synthesis of Functionalized Indanes.

Trifluoroacetic acid promoted unprecedented domino reaction for the synthesis of diverse indanes starting from simple cinnamic acid esters is described. Their formation can be explained via acid triggered decarboxylation of cinnamic acid esters and subsequent inter/intramolecular cyclization. Overall process involves in the intramolecular cleavage of two σ-bonds (C-O and C-C) and inter/intramolecular construction of two/one C-C σ-bond(s). Significantly, this protocol was successful without the aid of any metal salts.