Synthesis of heterocyclic systems involving [3,3]-sigmatropic rearrangements

The review summarizes the data on the synthesis of heterocyclic compounds by means of [3,3]-sigmatropic transformations, which include the Fischer, Claisen, and Cope rearrangements, as well as their numerous variations. These reactions have proved to be a convenient and efficient method for the synthesis of complex and poorly available heterocyclic systems with several chiral centers due to the highly ordered transition state of the process. Methods for the construction of five- and six-membered and medium size oxygen-, nitrogen-, and sulfur- containing heterocycles are described, as well as their use in the synthesis of condensed systems and natural compounds. © 2021, Springer Science+Business Media LLC

Synthesis of pyrrolo[1,2- d] [1,4]diazecines through an alkyne-trigged sequence of cleavage/cyclization in 1-phenylethynyl substituted pyrrolo[1,2- a] pyrazines

Transformations of 2-methyl-1-R-1-phenylethynyl-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazines under the action of electron-deficient alkynes in aprotic and protic solvents were studied. 1-Phenyl-1-phenylethynyl substituted pyrrolopyrazine did not react with alkynes or gave complex reaction mixtures. 1-Alkyl substituted 1-phenylethynyl-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazines in protic solvents underwent expansion to 8-alkylidene-6-phenyl-1,2,3,8-tetrahydropyrrolo[1,2-d][1,4]diazecines. © 2022 Author(s)

First synthesis of heterocyclic allenes-benzazecine derivatives

Benzazecines with an allene fragment were prepared for the first time and in high yields via tandem reaction of 1-phenylethynyl-1-methyl(benzyl)-1,2,3,4-tetrahydroisoquinolines with activated alkynes in trifluoroethanol. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique

The first synthesis of 6-(phenylethynyl)-substituted tetrahydroazocino[5,4-b]indoles

The reaction of 2-methyl-1-(phenylethynyl)-2,3,4,9-tetrahydro-1?-β-carboline with activated alkynes in acetonitrile led to the formation of 1-vinyl-substituted β-carbolines and condensed azocines. © 2016 Springer Science+Business Media New York

Unusual thermolysis of azacyclic allene under microwave conditions: Crystal structure of (3 RS,3a SR,8 RS,8a RS)-methyl 5,6-dimethoxy-3a,10-dimethyl-1-phenyl-3,3a,8,8a-tetrahydro-3,8-(epiminomethano)cyclopenta[ a ]indene-2-carboxylate from synchrotron X-ray diffraction

The title compound, C 25 H 27 NO 4 (I), the product of the unusual thermolysis of azacyclic allene methyl 10,11-dimethoxy-3,8-dimethyl-6-phenyl-3-azabenzo[d]cyclodeca-4,6,7-triene-5-carboxylate, represents a bicyclic heterosystem and crystallizes in the monoclinic space group P2 1 /c with three crystallographically independent molecules in the unit cell. These independent molecules adopt very similar geometries and differ only in the conformations of the two methoxy substituents on the benzene ring. In two of the three independent molecules, both methoxy groups are almost coplanar with the benzene ring [the C - C - O - Me torsion angles are 10.8(2), 12.3(2), 9.1(2) and 13.6(3)°], whereas in the third molecule, one of the methoxy groups is practically coplanar to and the other methoxy group is roughly perpendicular to the benzene ring, the C - C - O - Me torsion angles being 14.1(2) and 76.5(2)°. The molecule of (I) comprises a fused tetracyclic system containing two five-membered rings (cyclopentenes) and two six-membered rings (piperidine and benzene). The five-membered rings have the usual envelope conformation, with the methyl-subsituted C atom as the flap in each molecule, and the six-membered piperidine ring has a chair conformation. The methyl substituent at the N atom occupies the sterically favourable equatorial position. The carboxylate group lies almost within the basal plane of the parent cyclopentene ring [making dihedral angle of 11.68(8), 18.94(9) and 15.16(9)° in the three independent molecules], while the phenyl substituent is twisted by 48.26(6), 42.04(6) and 41.28(6)° (for the three independent molecules) relative to this plane. In the crystal, molecules of (I) form stacks along the b-axis direction. The molecules are arranged at van der Waals distances. © Anh et al. 2017

First synthesis of heterocyclic allenes-benzazecine derivatives

Benzazecines with an allene fragment were prepared for the first time and in high yields via tandem reaction of 1-phenylethynyl-1-methyl(benzyl)-1,2,3,4-tetrahydroisoquinolines with activated alkynes in trifluoroethanol. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique