Synthesis of 4-arylpyridines and substituted β-carbolines via 1,4-Grignard-addition to pyridinecarboxamides

Synthesis of fluorinated β-carbolines by one-pot reaction

This paper describes a new strategy for the synthesis of 1-trifluoromethyl-9H-pyrido [3,4-b]indole 2 by one-pot reaction of tryptophan methyl ester hydrochloride 1 and trifluoroacetic anhydride (TFAA) in the presence of POCI3 with satisfactory yield. Additionally, the structure of 2b was confirmed by X-ray crystallographic analysis.

A new synthetic approach to biaryls of the rhazinilam type. Application to synthesis of three novel phenylpyridine-carbamate analogues

The synthesis of three novel racemic phenylpyridine-carbamate analogues of rhazinilam and their biological evaluation as inhibitors of microtubule assembly and disassembly by interaction with tubulin are described. The sterically hindered ortho-disubstituted biaryl unit as the challenging key structural element is first obtained by a sequential regiocontrolled nucleophilic addition of a lithium ortho-lithiohomobenzylic alkoxide species to 3-bromo-5-oxazolyl pyridine as the electrophile and a subsequent oxidation step. The incorporation of the amino group by replacement of the bromide has been achieved using a Buchwald-Hartwig amination coupling. Ultimate deprotection steps furnished free-amino and free-hydroxyl appendages which were connected by phosgenation to furnish the nine-membered median carbamate ring.

Efficient Synthesis of Novel NK1Receptor Antagonists: Selective 1,4-Addition of Grignard Reagents to 6-Chloronicotinic Acid Derivatives

A new efficient synthesis of two novel classes of NK1 receptor antagonists, among them befetupitant and netupitant, starting from 6-chloronicotinic acid is described. The introduction of the o-tolyl substituent at C4 of the pyridine ring was achieved by a one-pot selective 1,4-Grignard addition/oxidation sequence to 6-chloronicotinic acid or a derivative of it. The scope of this addition/oxidation sequence was examined. It was also shown that the carboxylic function can be converted to a methyl amino group by a Hofmann rearrangement followed by reduction. Furthermore, a new high-yielding synthesis of 2-(3,5-bistrifluoromethylphenyl)-2-methyl propionic acid based on the carbonylation of the tertiary alcohol obtained by Grignard addition of 3,5-bis(trifluoromethyl)bromobenzene to acetone was established.

Deprotonation of benzoxazole and oxazole using lithium magnesates

The first deprotonations of oxazole and benzoxazole using lithium magnesates are described. The reactions occurred in tetrahydrofuran at room temperature using 1/3 equiv of lithium tributylmagnesate. As 2-lithiooxazole and 2-lithiobenzoxazole, lithium tri(2-oxazolyl)magnesate and lithium tri(2-benzoxazolyl)magnesate very rapidly and completely isomerized to the more stable 2-(isocyano)enolate and 2-(isocyano)phenolate type structures, respectively, a result shown by NMR analysis. The isolation of 2-substituted oxazoles and benzoxazoles in medium to good yields after electrophilic trapping was interpreted in two ways: (1) the equilibration between the open and closed structures is faster than the trapping of the open isomers, and the closed isomers are more reactive than the open ones, or (2) the open isomers react with electrophiles in a intramolecular Passerini type reaction. The nonreactivity of the 2-(isocyano)enolate type structure toward anisaldehyde in the absence of lithium bromide makes the intramolecular Passerini type reaction more plausible.

3-Aryl β-carbolin-1-ones as a new class of potent inhibitors of tumor cell proliferation: synthesis and biological evaluation

A novel three-step synthesis of 3-aryl beta-carbolin-1-ones from non-indole starting materials has been developed. The two nitrogen atoms in beta-carbolin-1-one were introduced efficiently by Michael addition of ethyl acetamidocyanoacetate to chalcone. The desired pyridone and indole rings were assembled by an intramolecular ketone-nitrile annulation mediated by aqueous HCl-HOAc and a Cu(I)-catalyzed intramolecular N-arylation of the amide, respectively. The target compounds were found to possess significant activity against tumor cell proliferation.

CuI catalyzed N-arylation of amide as a key step for the preparation of 3-aryl β-carbolin-1-ones

An expedient synthetic route for 3-aryl beta-carbolin-1-ones was developed starting from ethyl acetamidocyanoacetate and chalcone derivatives. The five- and six-membered nitrogen-containing rings in the beta-carbolin-1-ones were elaborated efficiently by an intramolecular ketone-nitrile annulation and an intramolecular N-arylation of amide respectively.