Leveraging cascade alkynyl Prins cyclization towards the stereoselective synthesis of spiro-furan quinazolinone scaffolds.

A TfOH-promoted, metal-free protocol has been unveiled for the synthesis of spiro-furan quinazolinones employing alkynol urea derivatives utilizing alkynyl Prins cyclization reaction. This methodology produces highly functionalized spiro-heterocycles in excellent yields with exclusive -selectivity under ambient conditions. Furthermore, late-stage modifications incorporate bromide and acetyl functionalities into the synthesized spiro-heterocycles.

Diastereoselective Synthesis of 2,6-Disubstituted Tetrahydropyranones via Prins Cyclization of 3-Bromobut-3-en-1-ols and Aldehydes.

Tetrahydropyranones are synthesized from 3-bromobut-3-en-1-ols and aldehydes in good yields with excellent diastereoselectivity at -35 °C. The reaction involves an initial formation of a most stable six-membered chairlike tetrahydropyranyl carbocation followed by nucleophilic attack of the hydroxyl group and subsequent elimination of HBr to give tetrahydropyranone. The carbonyl moiety of the tetrahydropyranone is converted to enol ether and esters using Wittig reaction.

Temperature Tunable Synthesis of Tetrahydro-4-pyrrolo[3,2-]quinolin-4-ones and Dihydro-1-benzo[]azepines from 2-Aminobenzonitriles and Donor-Acceptor Cyclopropanes.

Tetrahydro-4-pyrrolo[3,2-]quinolin-4-ones and dihydro-1-benzo[]azepines are efficiently synthesized from 2-aminobenzonitriles and donor-acceptor cyclopropanes mediated by SnCl in moderate to good yields. The reaction involves the initial ring opening of a cyclopropane ring due to activation by SnCl followed by nucleophilic attack by amine to give an adduct, which after unprecedented rearrangement at two different reaction temperatures provides two nitrogen heterocyclic compounds. This methodology can be used for the synthesis of hexahydropyrrolo[3,2-]quinolinone derivatives, the structure of which is found in biologically active molecules.

Synthesis of Spiro[furan-2,1'-isoindolin]-3'-ones from 2-(4-Hydroxybut-1-yn-1-yl)benzonitriles and Aryl Aldehydes under the Action of Triflic Acid.

The synthesis of spiro[furan-2,1'-isoindolin]-3'-ones from 2-(4-hydroxybut-1-yn-1-yl)benzonitriles and aryl aldehydes is demonstrated. It involves the initial formation of dihydrofuranylideneisoindolinone via intramolecular sequential Prins and Ritter reactions, followed by the ring opening of the furanyl moiety to generate -acyliminium ions and alcohols for the final cyclization reaction, and the spiro-cyclic compounds are produced in moderate to good yields. It is a one-pot, three-component reaction in which one new quaternary carbon, two five-membered rings, one C-N bond, two C-O bonds, and one C-C bond are formed.

KSO-Mediated Synthesis of Highly Functionalized Pyrroles via Oxidative Self-Dimerization of -Propargylamines.

An efficient methodology has been developed for the synthesis of tetra- and pentasubstituted pyrroles via oxidative self-dimerization of -propargylamines catalyzed by silver benzoate in the presence of KSO in good yields. The protocol provides a simple route for the synthesis of both tetra- and pentasubstituted pyrroles with two carbonyl groups in the side chain. The methodology can be extended toward the synthesis of pyrrolo[3,4-]pyridazine.

In(OTf)-Catalyzed One-Pot Tandem Mannich and Conia-Ene Cyclization Reaction of -Propargyl Amido Alcohols with 1,3-Dicarbonyl Compounds: An Approach To Construct Tetrahydro-1-pyrrolo[2,1-]isoindolone-1,1-dicarboxylate and Its Application.

A one-pot tandem reaction has been developed for the synthesis of substituted tetrahydropyrroloisoindolone via Mannich reaction of -propargyl amido alcohols with 1,3-dicarbonyl compounds followed by Conia-ene cyclization reaction in moderate to good yields catalyzed by indium(III)triflate [In(OTf)]. The reaction is highly regioselective with an exo-cyclic double bond in the pyrrolidine ring. The substituted tetrahydropyrroloisoindolone can be converted to 5-pyrrolo[2,1-]isoindol-5-one via decarboxylative aromatization reaction.