Chemoselectivity-independent Cu-mediated coupling to construct the hydroquinoline skeleton of symbioimine

Construction of the hydroquinoline skeleton of symbioimine by Cu-mediated N-alkenylation or O-alkenylation of an allyl aminoalcohol, in which either chemoselectivity could lead to the target compound, was investigated. O-alkenylation followed by Claisen rearrangement was favored with high selectivity under a ligand-free condition. Subsequent intramolecular condensation furnished the hydroquinoline skeleton of symbioimine.

A Domino Heck Coupling–Cyclization–Dehydrogenative Strategy for the One-Pot Synthesis of Quinolines

An efficient, one-pot, domino synthesis of quinolines via the coupling of iodoanilines with allylic alcohols facilitated by palladium catalysis is described. The overall synthetic process involves an intermolecular Heck coupling between 2-iodoanilines and allylic alcohols, intramolecular condensation of in situ generated ketones with an internal amine functional group, and a dehydrogenation sequence. Notably, this protocol occurs in water as a green solvent. Significantly, the method exhibits broad substrate scope and is applied for the synthesis of deuterated quinolines through a deuterium-exchange process.

One-Pot Synthesis of Novel Multisubstituted 1-Alkoxyindoles

Studies on a one-pot synthesis of novel multisubstituted 1-alkoxyindoles 1 and their mechanistic investigations are presented. The synthesis of 1 was successfully achieved through consecutive four step reactions from substrates 2. The substrates 2, prepared through a two-step synthetic sequence, underwent three consecutive reactions of nitro reduction, intramolecular condensation, and nucleophilic 1,5-addition to provide the intermediates, 1-hydroxyindoles 8, which then were alkylated in situ with alkyl halide to afford the novel target products 1. We optimized the reaction conditions for 1 focusing on the alkylation step, along with the consideration of formation of intermediates 8. The optimized condition was SnCl2·2H2O (3.3 eq) and alcohols (R1OH, 2.0 eq) for 1–2 h at 40 °C and then, base (10 eq) and alkyl halides (R2Y, 2.0 eq) for 1–4 h at 25–50 °C. Notably, all four step reactions were performed in one-pot to give 1 in good to modest yields. Furthermore, the mechanistic aspects were also discussed regarding the reaction pathways and the formation of side products. The significance lies in development of efficient one-pot reactions and in generation of new 1-alkoxyindoles.

Consecutive reactions to construct tricarbonyl compounds and synthetic applications thereof

A cascade process to construct synthetically valuable β-keto-β′-acylcycloalkanecarboxylic acid esters and their transformation into bicyclic and tricyclic systems through intramolecular condensation reactions.

2-Carbamimidoylbenzoic Acid as a New Effective and Available Precursor for the Synthesis of Substituted 2-(Pyrimidin-2-yl)benzoic Acids

A new approach to the synthesis of 2-(pyrimidin-2-yl)benzoic acids based on the ring contraction of the 2-carbamimidoylbenzoic acid [(2-amidinobenzoic) acid] with 1,3-dicarbonyl compounds and their synthetic equivalents has been developed. The intramolecular condensation of the obtained acids with 1,3-dielectrophiles proceeds with the formation of the 4,6-dihydropyrimido[2,1-a]isoindole-4,6-dione system, the pyrrolidone ring of which is easily opened under the action of weak nucleophiles. The reaction of 2-amidinobenzoic acid with chromones, which have an aryloxy group at 3-position does not stop at the step of pyrimidine ring formation and undergoes further spontaneous cyclization into 2-(benzo[4,5]furo[3,2-d]pyrimidin-2-yl)benzoic acids.

Reductive Condensation of a Nitro Group with Carboxylic Acids Promoted by Phosphorus(III) Compounds: A Short Route to 5H-Dibenzo[b,e][1,4]diazepin-11(10H)-ones

Tributyl- or triphenylphosphine promotes a one-pot, three-step method for the synthesis of differently substituted dibenzodiazepinones from N-aryl-2-nitroanilines. Pyridine analogues and the corresponding thiazepinones can also be formed using this method. The process involves deoxygenation of the nitro group, then formation of an iminophosphorane intermediate and its intramolecular condensation with a carboxyl group placed in the N-aryl group. The role of the carboxyl group in the formation of the iminophosphorane and the mode of cyclization are discussed.

Synthesis and Structural Characterization of Some 1,3-Dithiol-2-ylium Salts

A new series of 2-(dialkylamino)-1,3-dithiol-2-ylium cations derived from acetophenones and propiophenones was synthesized by the intramolecular condensation of appropriate substituted dithiocarbamates. The structural characterization of the new compounds has been performed by NMR and IR analysis. The structure of 1,3-dithiol-2-ylium perchlorate 3e has been proved by X-Ray analysis.

Rh-Catalyzed C–H activation/intramolecular condensation for the construction of benzo[f]pyrazolo[1,5-a][1,3]diazepines

A novel and mild Rh(iii)-catalyzed cascade C–H activation/intramolecular condensation of 1-aryl-1H-pyrazol-5-amines with cyclic 2-diazo-1,3-diketones for the synthesis of various important benzo[f]pyrazolo[1,5-a][1,3]diazepines has been developed.