Dienophilic reactivity of 2-phosphaindolizines: a conceptual DFT investigation

• Nosheen Beig,
• Aarti Peswani and
• Raj Kumar Bansal

Beilstein J. Org. Chem. 2022, 18, 1217–1224, doi:10.3762/bjoc.18.127

• -diazaphospholo[1,2-a]pyridines, i.e., 1-aza-2-phosphaindolizines 3 [2], 1,2,3-diazaphospholo[1,5-a]pyridines, i.e., 3-aza-2-phosphaindolizines 4 [3], and 1,2,4,3-triazaphospholo[1,5-a]pyridine, i.e., 1,3-diaza-2-phosphaindolizine (5, Figure 2) [4]. We succeeded in developing another method involving a 1,5

• -electrocyclization of the initially formed pyridinium alkoxycarbonyl-dichlorophosphinomethylide followed by 1,2-elimination affording 1,3-bis(alkoxycarbonyl)-2-phosphaindolizines [5]. After having access to a good number of differently substituted derivatives of these four classes of 2-phosphaindolizines, we were

Unusual highly diastereoselective Rh(II)-catalyzed dimerization of 3-diazo-2-arylidenesuccinimides provides access to a new dibenzazulene scaffold

• Anastasia Vepreva,
• Alexander S. Bunev,
• Andrey Yu. Kudinov,
• Grigory Kantin,
• Mikhail Krasavin and
• Dmitry Dar’in

Beilstein J. Org. Chem. 2022, 18, 533–538, doi:10.3762/bjoc.18.55

• analysis (see Supporting Information File 1). A plausible mechanism of the observed transformations of DAS (shown for 1a) is presented in Scheme 2. The initially formed rhodium carbene A undergoes 1,5-electrocyclization to form intermediate B which turns into indene C as the result of a 1,5-suprafacial

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

Dialkyl dicyanofumarates and dicyanomaleates as versatile building blocks for synthetic organic chemistry and mechanistic studies

• Grzegorz Mlostoń and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2017, 13, 2235–2251, doi:10.3762/bjoc.13.221

• mechanistic explanation of this cyclopropanation reaction is based on the assumption that the intermediate zwitterion 18a undergoes either a 1,3- or 1,5-electrocyclization leading to 15 or thiolanes 19a. The experiments with both isomers of 1b showed that the reactions proceeded non-stereospecifically and

Synthesis of 2,1-benzisoxazole-3(1H)-ones by base-mediated photochemical N–O bond-forming cyclization of 2-azidobenzoic acids

• Daria Yu. Dzhons and
• Andrei V. Budruev

Beilstein J. Org. Chem. 2016, 12, 874–881, doi:10.3762/bjoc.12.86

• -benzisoxazolones; 1,5-electrocyclization; nitrenes; photochemical cyclization; Introduction Substituted 2,1-benzisoxazoles display diverse biological activity [1][2][3][4][5][6] (Figure 1) and are widely used as starting materials for the synthesis of important heterocyclic pharmacophores, such as acridines [7][8

• through a 1,5-electrocyclization reaction [56][57]. Nonreacted singlet nitrenes A may undergo intersystem crossing (ISC) into the less reactive triplet state (Scheme 1, intermediate D). Although a multiplicity change is a spin-forbidden transition, it can be partially allowed in some cases. According to

• . Finally, the electron pair of the carboxylic group (Scheme 2, intermediate A) was joined by 1,5-electrocyclization to the electron-deficient singlet nitrene A with formation of 2-anion (see Scheme 2), which was neutralized by water (path I). Thus, the first path of cyclization of 1 was realized. Meanwhile

Tandem processes promoted by a hydrogen shift in 6-arylfulvenes bearing acetalic units at ortho position: a combined experimental and computational study

• Mateo Alajarin,
• Marta Marin-Luna,
• Pilar Sanchez-Andrada and
• Angel Vidal

Beilstein J. Org. Chem. 2016, 12, 260–270, doi:10.3762/bjoc.12.28

• geometry of transition structures TS1-A, TS1-B, and TS1-C computed at the B3LYP/6-31+G** theoretical level. Distances in Ångstroms, bond angles in degrees. Lewis acid-catalyzed [1,4]-H transfer/1,5-electrocyclization tandem processes of benzylidenemalonates 1 leading to indan-1-ones 2. Preparation of benz

On the strong difference in reactivity of acyclic and cyclic diazodiketones with thioketones: experimental results and quantum-chemical interpretation

• Andrey S. Mereshchenko,
• Alexey V. Ivanov,
• Viktor I. Baranovskii,
• Grzegorz Mloston,
• Ludmila L. Rodina and
• Valerij A. Nikolaev

Beilstein J. Org. Chem. 2015, 11, 504–513, doi:10.3762/bjoc.11.57

• =S ylides bearing at least one acyl group is identified as the 1,5-electrocyclization into 1,3-oxathioles. However, in the case of diazomalonates, the dominating process is 1,3-cyclization into thiiranes followed by their spontaneous desulfurization yielding the corresponding alkenes. Finally

• thermodynamically allowed in both directions. However, based on the relative values of ΔG1 and ΔG2 for thiocarbonyl ylides 7a–c and 7'a–c (Table 3, entries 1–3 and 7–9), the 1,5-electrocyclization leading to 1,3-oxathioles 3a–c and 3'a–c is a thermodynamically more favorable process. However, in the case of the

• diazomalonate derivatives 7d and 7’d (Table 3, entries 4 and 10), the 1,3-electrocyclization process is thermodynamically preferable, resulting in the formation of thiiranes 4d and 4'd. At the same time, from the kinetic point of view, the 1,5-electrocyclization process is more efficient because the activation

Less reactive dipoles of diazodicarbonyl compounds in reaction with cycloaliphatic thioketones – First evidence for the 1,3-oxathiole–thiocarbonyl ylide interconversion

• Valerij A. Nikolaev,
• Alexey V. Ivanov,
• Ludmila L. Rodina and
• Grzegorz Mlostoń

Beilstein J. Org. Chem. 2013, 9, 2751–2761, doi:10.3762/bjoc.9.309

• react at room temperature with cycloaliphatic thioketones, e.g. 2,2,4,4-tetramethyl-3-thioxocyclobutanе-1-one and adamantanethione, via a cascade process in which the key step is a 1,5-electrocyclization of the intermediate thiocarbonyl ylide leading to tetrasubstituted spirocyclic 1,3-oxathioles. The

• the thiocarbonyl ylide 6 is also possible via an alternative pathway C, that implies interaction of a dioxocarbene (formed after thermal decomposition of the diazo compound) with the sulfur atom of the C=S group [4][7][8]. The subsequent intramolecular 1,5-electrocyclization of the same intermediate 6

• are 15.2 and 26.6 kcal·mol−1, respectively (see Supporting Information File 1, Table S1). Based on these data domination of 1,5-electrocyclization of C=S-ylide 6e' at room temperature can be apparently explained by the rather high difference (6.6 kcal·mol−1) between transition states energy levels TS1

Asymmetric Diels–Alder reaction with >C=P– functionality of the 2-phosphaindolizine-η¹-P-aluminium(O-menthoxy) dichloride complex: experimental and theoretical results

• Rajendra K. Jangid,
• Nidhi Sogani,
• Neelima Gupta,
• Raj K. Bansal,
• Moritz von Hopffgarten and
• Gernot Frenking

Beilstein J. Org. Chem. 2013, 9, 392–400, doi:10.3762/bjoc.9.40

• theoretically as well as experimentally [16]. In this context, we found that 1,3-bis(alkoxycarbonyl)-2-phosphaindolizines (1a, Z = CO2R1) prepared through 1,5-electrocyclization of in situ generated bis(pyridinium ylidyl)phosphenium chlorides [17] lead to successful DA reaction [18][19], but 3-alkoxycarbonyl-2