T. Q. Tran

Regioselective cycloaddition of C-aryl- and C-carbamoylnitrones to methyl 2-benzylidenecyclopropanecarboxylate

C-Aryl- and C-carbamoylnitrones reacted with methyl 2-benzylidenecyclopropanecarboxylate in highly regioselective fashion to give the corresponding 1,3-dipolar cycloaddition products, substituted methyl 5-oxa-6-azaspiro[2.4]heptane-1-carboxylates as mixtures of two diastereoisomers.

Methyl (E)-2-(2-phenylcyclopropylidene)acetate: Synthesis, isomerization, and reaction with 1,3-diphenyl-2-benzofuran

Treatment of 3-methyl-2-phenylcycloprop-2-ene-1-carboxylic acid with potassium tert-butoxide induced its isomerization into trans-2-methylidene-3-phenylcyclopropane-1-carboxylic acid which was converted into methyl ester, and heating of the latter for 1 h in toluene gave methyl (E)-2-(2-phenylcyclopropylidene)acetate. Thermal isomerization of methyl (E)-2-(2-phenylcyclopropylidene)acetate on prolonged heating in toluene afforded 5-methoxy-3-methyl-2-phenylfuran, and the reaction with 1,3-diphenyl-2-benzofuran resulted in [4 + 2]-cycloaddition at the exocyclic double bond.

Regioselective cycloaddition of C-carbamoylnitrones to methyl (E)-2-(2-phenylcyclopropylidene)acetate and methyl (E)-2-methylidene-3-phenylcyclopropane-1-carboxylate

N-Aryl-C-(arylcarbamoyl)nitrones regioselectively add to methyl 2-(2-phenylcyclopropylidene)-acetate and methyl 2-methylidene-3-phenylcyclopropanecarboxylate to give in each case two diastereoisomeric 5-oxa-6-azaspiro[2.4]heptane-4-carboxylates.

Reductive cleavage and subsequent transformations of 5-oxa-6-azaspiro[2.4]heptane-1-carboxylates

Treatment of methyl 4,6-diaryl-5-oxa-6-azaspiro[2.4]heptane-1-carboxylates with zinc in acetic acid leads to cleavage of the N–O bond in the isoxazolidine ring with formation of 1,3-amino alcohols whose subsequent cyclization under the reaction conditions yields bi- or tricyclic lactams or lactones with retention of the three-membered ring.

Reduction and hydrolysis of substituted 5-oxa-6-azaspiro[2.4]heptane-1,2-dicarboxylic acid esters

Substituted 5-oxa-6-azaspiro[2.4]heptane-1,2-dicarboxylic acid esters synthesized by reaction of nitrones with dimethyl 3-methylidenecyclopropane-1,2-dicarboxylate were reduced with lithium tetrahydridoaluminate to the corresponding bis(hydroxymethyl)cyclopropanes. Alkaline hydrolysis of the title compounds gave substituted cyclopropane-1,2-dicarboxylic acids. In both cases, the 5-oxa-6-azaspiro[2.4]heptane fragment remained intact.

Oxidation of reaction products of p -aryl- С , С -disubstituted nitrones and dimethyl 3-methylenecyclopropane-1,2-dicarboxylate

Oxidation with 2,3-dichloro-4,5-dicyanobenzoquinone of 2,4-dihydro-1Н-azeto[1,2-a]quinoline-3,4 -dicarboxylates obtained in the reaction of N-aryl-С,С-disubstituted nitrones with Feist’s acid ester resulted in the formation of 2-vinylquinoline-3,4-dicarboxylates in good yields.

Corrigendum to “An efficient method of synthesis of isoxazolidine-fused β-lactams via base-promoted cyclization-ring opening of carbamoyl-spirocyclopropane isoxazolidines” [Tetrahedron 69 (2013) 5173–5177]

Corrigendum to “An efficient method of synthesis of isoxazolidinefused b-lactams via base-promoted cyclization-ring opening of carbamoyl-spirocyclopropane isoxazolidines” [Tetrahedron 69 (2013) 5173e5177] Tung Q. Tran , Ruslan S. Savinkov , Vyacheslav V. Diev , Galina L. Starova , Alexander P. Molchanov b,* a School of Chemical Engineering, Hanoi University of Science and Technology, 1 Dai Co Viet Road, Ha Noi, Viet Nam Department of Chemistry, Saint Petersburg State University, Universitetsky pr. 26, Saint Petersburg 198504, Russian Federation Department of Chemistry, University of Southern California, Los Angeles, CA 90089, USA