E- or Z-Selective Knoevenagel Condensation of Acetoacetic Derivatives: Effect of Acylated Substituent, that is, TEMPO and Amines, as an Auxiliary, and New Accesses to Trisubstituted E- and Z-2-Alkenals and Furans

Doubly stereoconvergent crystallization enabled by asymmetric catalysis

Synthetic methods that enable simultaneous control over multiple stereogenic centers are desirable for the efficient preparation of pharmaceutical compounds. Herein, we report the discovery and development of a catalyst-mediated asymmetric Michael addition/crystallization-induced diastereomer transformation of broad scope. The sequence controls three stereogenic centers, two of which are stereochemically labile. The configurational instability of 1,3-dicarbonyls and nitroalkanes, typically considered a liability in stereoselective synthesis, is productively leveraged by merging enantioselective Brønsted base organocatalysis and thermodynamic stereocontrol using a single convergent crystallization. The synthesis of useful γ-nitro β-keto amides containing three contiguous stereogenic centers is thus achieved from Michael acceptors containing two prochiral centers.

Formation of Highly Substituted Indenes through Acid Promoted Cyclodehydration with Nucleophile Incorporation

Readily accessible 3-aryl-2-carboxypropenones (by Knoevenagel condensation) undergo acid promoted cyclodehydration with nucleophile incorporation to form highly substituted indenes. For stronger nucleophiles, nucleophile incorporation precedes cyclodehydration in a nucleophilic-addition-cyclodehydration (NAC) sequence. For weaker nucleophiles, cyclodehydration precedes nucleophile incorporation in a cyclodehydrative-nucleophilic-trapping (CNT) sequence, involving a reactive allyl cation intermediate. The substrate scope and preferred cyclization pathway (NAC or CNT) has been studied with respect to 3-aryl-2-carboxypropenone and the nature of the nucleophile. Also, for 1,3-diaryl-2-carboxypropenones, which can also undergo Nazarov cyclization, delineation between competing Nazarov and CNT pathways is controlled by the nature of the acid catalyst.

Stereoconvergent 1,4-Addition Reaction of 5H-Oxazol-4-ones with E,Z Isomeric Mixture of Alkylidene β-Ketoesters Catalyzed by Chiral Guanidines

A 1,4-addition reaction of 5H-oxazol-4-ones to alkylidene β-ketoesters, which was catalyzed by using chiral guanidines via a dynamic kinetic resolution process that involved geometric isomerization of the alkylidene β-ketoesters, was developed. This method allowed using E,Z isomeric mixture of various acyclic alkylidene β-ketoesters to obtain the products stereoselectively. The relation between the geometry and the stereoselectivity of products was investigated, and the derivatization of the products to the corresponding α-acyl-γ-lactone was performed.

Design for carbon–carbon bond forming reactions under ambient conditions

The carbon–carbon (C–C) bond forms the ‘backbone’ of nearly every organic molecule, and lies at the heart of the chemical sciences! Let us explore designing of carbon–carbon frameworks at ambient conditions.

Cytotoxic 2-phenyacrylnitriles, the importance of the cyanide moiety and discovery of potent broad spectrum cytotoxic agents

We previously reported the discovery of a simple conjugated cyano pharmacophore which had led to the development of (Z)-2-(3,4-dichlorophenyl)-3-(4-nitrophenyl)acrylonitrile, as a selective inhibitor of oestrogen receptor positive (ER+ve) human breast cancer cell line, MCF-7. Further exploration though modification of the acrylonitrile and aromatic substituents has highlighted key structural components necessary for broad spectrum cytotoxicity. The acrylic acid derivates (Z)-2-(3,4-dichlorophenyl)-3-(4-nitrophenyl)acrylic acid and (Z)-2-(3,4-dichlorophenyl)-3-(4-methoxyphenyl)acrylic acid (9) were inactive; confirming the importance of the cyanide moiety. The most potent 2-phenylacrylonitriles synthesized were (Z)-2-(3,4-dichlorophenyl)-3-(1H-indol-3-yl)acrylonitrile and (Z)-2-(3,4-dichlorophenyl)-3-(1H-indol-5-yl)acrylonitrile (20) with an average GI(50) values of 1.4 and 0.53 μM respectively. Five additional (Z)-2-(3,4-dichlorophenyl)-3-(indolyl)acrylonitriles also displayed average GI(50) values of ≤8.4 μM. In the case of indole, this represents a 32-fold increase in broad spectrum cytotoxicity relative to the lead.

Synthesis and biological evaluation of benzyl styrylsulfonyl derivatives as potent anticancer mitotic inhibitors

We herein report the synthesis, biological activity and structure activity relationship of derivatives of benzylstyrylsulfone, benzylstyrylsulfine and benzylsulfonyl-N-phenylacetamide. A lead compound 7 represents a new class of mitotic inhibitors that demonstrates potent anti-proliferative activity and selectively induces cancer cell apoptosis while sparing non-transformed lung fibroblast.

Enantio- and diastereoselective intermolecular Stetter reaction of glyoxamide and alkylidene ketoamides

A triazolinylidene carbene catalyzed intermolecular Stetter reaction of glyoxamide and alkylidene ketoamides has been developed. 1,4-Dicarbonyl products are afforded in good to excellent yields, enantioselectivities, and diastereoselectivities. Further derivatization of the products affords useful intermediates for organic synthesis.

A highly efficient preparative method of alpha-ylidene-beta-diketones via Au(III)-catalyzed acyl migration of propargylic esters

A highly efficient synthesis of alpha-alkylidene or benzylidene-beta-diketones from readily available propargylic esters has been developed. The proposed key transformation is a novel intramolecular acyl migration to nucleophilic AuIII-C(sp2) bonds. Noteworthy features of this method are its efficiency and stereoselectivity. The yields of this reaction were mostly close to quantitative, and high to excellent stereoselectivities were observed in the cases of dienyl beta-diketones.

Alkylation, Aldol, and Related Reactions of O-Alkanoyl- and 2-AlkenoylTEMPOs (2,2,6,6-Tetramethylpiperidine-N-oxyl): Insight into the Reactivity of Their Anionic Species in Comparison with Esters and Amides

The lithium anionic species generated from O-alkanoylTEMPOs upon treatment with LDA were first employed as a nucleophile for alkylation, Michael addition, direct aldol reaction, and others. The alkylation occurred smoothly at the methylene carbon, and no alkylation was found in the isobutyryl analogue, while silylation was scarcely attainable. Substitutions of the heteroatom were achieved by reaction with PhSSPh and DEAD. The reactivity of these anionic species is successfully extended to aldol reactions in which moderate anti or syn selectivity was executed with propionyl derivatives. Tandem Michael addition of lithium amide followed by aldol reaction was performed on the O-crotonoylTEMPOs.