α,γ-Dioxygenated amides via tandem Brook rearrangement/radical oxygenation reactions and their application to syntheses of γ-lactams

• Mikhail K. Klychnikov,
• Radek Pohl,
• Ivana Císařová and
• Ullrich Jahn

Beilstein J. Org. Chem. 2021, 17, 688–704, doi:10.3762/bjoc.17.58

• lactams 12a–k in 66–93% yields. The thermal cyclization of α-(aminoxy)amide 9a provided two diastereomers of lactam 12a in a 2:1 trans/cis ratio (Table 3, entry 1). The N-allylic amides 9b–f provided lactams 12b–f as mixtures of four inseparable diastereomers in which those with trans orientation of the

• -(aminoxy)-γ-(silyloxy)amides 9l–p with cyclic units are also suitable precursors for radical cyclization reactions (Scheme 3). 3-(2-Hydroxycyclohexyl)-2-pyrrolidone 12l was obtained by the thermal cyclization of α-(aminoxy)cyclohexylacetamide 9l as a mixture of two major trans isomers 12lA and 12lB, which

• were accompanied by traces of a C3–C4 cis-diastereomer (not shown). The relative configuration of pyrrolidone 12l was assigned by NOE experiments of 3-(2-oxocyclohexyl)lactams 13l prepared from 12l by Dess–Martin oxidation (vide infra). The thermal cyclization of compounds 9m,n with N

Reactions of 3-aryl-1-(trifluoromethyl)prop-2-yn-1-iminium salts with 1,3-dienes and styrenes

• Thomas Schneider,
• Michael Keim,
• Bianca Seitz and
• Gerhard Maas

Beilstein J. Org. Chem. 2020, 16, 2064–2072, doi:10.3762/bjoc.16.173

• and therefore, are candidates for polar Diels–Alder reactions [40][41]. The thermal cyclization of Diels–Alder adducts as shown in Scheme 2 and Scheme 3 appear to be the first intramolecular SE(Ar) reactions of an α-(trifluoromethyl)iminium functional group. Analogous intermolecular reactions of CF3

Synthesis of unnatural α-amino esters using ethyl nitroacetate and condensation or cycloaddition reactions

• Glwadys Gagnot,
• Vincent Hervin,
• Eloi P. Coutant,
• Sarah Desmons,
• Racha Baatallah,
• Victor Monnot and
• Yves L. Janin

Beilstein J. Org. Chem. 2018, 14, 2846–2852, doi:10.3762/bjoc.14.263

• cleaved using palladium and ammonium formate to give the corresponding oximes which were immediately reduced into amines 22a,b, using zinc and hydrochloric acid, and a thermal cyclization of these crude products gave the piperazine-2,5-diones 23a,b in, respectively, 31 and 40% overall yield from compound

Oxidative and reductive cyclization in stiff dithienylethenes

• Michael Kleinwächter,
• Ellen Teichmann,
• Lutz Grubert,
• Martin Herder and
• Stefan Hecht

Beilstein J. Org. Chem. 2018, 14, 2812–2821, doi:10.3762/bjoc.14.259

• not observed (Figure 2a and b), suggesting a concerted two-electron oxidation of the open isomers and thermal cyclization in the dicationic state (vide infra). Influence of ring size and substitution To correlate structural parameters with the observed electrochemical behavior, sDTEs with other ring

• ][47] as the key intermediate undergoing thermal cyclization or cycloreversion, typically in the context of so-called “ECE” and “EEC” mechanisms, respectively [48]. To contribute to this discussion, nonsymmetrical DAEs bearing two electronically distinct aryl moieties (CF3- and Me-thiazole) [5] or

Solving the puzzling competition of the thermal C²–C⁶ vs Myers–Saito cyclization of enyne-carbodiimides

• Anup Rana,
• Mehmet Emin Cinar,
• Debabrata Samanta and
• Michael Schmittel

Beilstein J. Org. Chem. 2016, 12, 43–49, doi:10.3762/bjoc.12.6

• Anup Rana Mehmet Emin Cinar Debabrata Samanta Michael Schmittel Department of Chemistry and Biology, Universität Siegen, Adolf-Reichwein-Str. 2, D-57068 Siegen, Germany 10.3762/bjoc.12.6 Abstract The mechanism of the thermal cyclization of enyne-carbodiimides 7a–c has been studied computationally

• pathway if the trapping reaction by hydrogen transfer is no more rate determining. Keywords: DFT computation; diradical; enyne-carbodiimides; hydrogen transfer; thermal cyclization; Introduction The thermal cyclizations of enediynes [1][2][3][4][5][6], enediallenes [7][8][9][10], bisallenes [11], enyne

• Myers–Saito product 3a, whereas the thermolysis of enyne-carbodiimide 1b produced the C2–C6 product 6b. In 1999 Wang et al. [19] stated that the thermal cyclization of enyne-carbodiimides 1c furnished C2–C6 (Schmittel) products 6c in p-xylene under reflux conditions. Based on the experimental findings

Radical-mediated dehydrative preparation of cyclic imides using (NH₄)₂S₂O₈–DMSO: application to the synthesis of vernakalant

• Dnyaneshwar N. Garad,
• Subhash D. Tanpure and
• Santosh B. Mhaske

Beilstein J. Org. Chem. 2015, 11, 1008–1016, doi:10.3762/bjoc.11.113

• the literature [28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45]. Thermal cyclization processes are still the preferred way for the synthesis of polyimides from the intermediate polyamic acid, which is heated in high boiling solvents (>200 °C) with continuous removal of water by

Development of peptidomimetic ligands of Pro-Leu-Gly-NH₂ as allosteric modulators of the dopamine D₂ receptor

• Swapna Bhagwanth,
• Ram K. Mishra and
• Rodney L. Johnson

Beilstein J. Org. Chem. 2013, 9, 204–214, doi:10.3762/bjoc.9.24

• to generate the spiro-bicyclic systems was accomplished by two different methods. In one approach, thermal cyclization of 35 and 36 followed by esterification gave the cyclized 5.5.5- and 5.5.6-spiro bicyclic products, 39 and 40, respectively [44][46]. In this approach, only one of two possible

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225

Cyclization of ortho-hydroxycinnamates to coumarins under mild conditions: A nucleophilic organocatalysis approach

• Florian Boeck,
• Max Blazejak,
• Markus R. Anneser and
• Lukas Hintermann

Beilstein J. Org. Chem. 2012, 8, 1630–1636, doi:10.3762/bjoc.8.186

• ), 45.0 (2 × CH2), 12.4 (2 × CH3) ppm. See Supporting Information File 1 for experimental details and NMR spectra of coumarins and the precursor 2’-hydroxycinnamates. Conditions for the cyclization of 2’-hydroxycinnamate and related precursors to coumarins. (a) Thermal cyclization [16]. (b) Photochemical

Microwave- assisted ring closure reactions: Synthesis of 8-substituted xanthine derivatives and related pyrimido- and diazepinopurinediones

• Joachim C. Burbiel,
• Jörg Hockemeyer and
• Christa E. Müller

Beilstein J. Org. Chem. 2006, 2, No. 20, doi:10.1186/1860-5397-2-20

• microwave irradiation. Furthermore, we showed that application of microwaves considerably improves the cyclization step to obtain tricyclic pyrimido [1,2,3-cd]purinediones. 2-Substituted diazepino [1,2,3-cd]purinediones, that had previously not been accessible by thermal cyclization [6] could be obtained in

Trapping evidence for the thermal cyclization of di-(o-acetylphenyl)acetylene to 3,3'-dimethyl- 1,1'-biisobenzofuran

• Charles P. Casey,
• Neil A. Strotman and
• Ilia A. Guzei

Beilstein J. Org. Chem. 2005, 1, No. 18, doi:10.1186/1860-5397-1-18

• the transient production of A, the first biisobenzofuran. An X-ray crystal structure of meso-3 was obtained. As part of a recent study of the thermal cyclization of η2-(o-ethynylbenzoyl)rhenium complexes to rhenium isobenzofuryl carbene complexes (Scheme 1),[1] we attempted to form a rhenium complex

• data for all new compounds and X-ray crystallographic data for meso-3 (16 pages). X-ray crystallographic data for meso-3 has been deposited in the Cambridge Structural Database (CCDC # 289103). X-ray crystal structure of meso-3. Thermal cyclization of η2-(o-ethynylbenzoyl)rhenium complexes to rhenium