Recent advances in the tandem annulation of 1,3-enynes to functionalized pyridine and pyrrole derivatives

• Yi Liu,
• Puying Luo,
• Yang Fu,
• Tianxin Hao,
• Xuan Liu,
• Qiuping Ding and
• Yiyuan Peng

Beilstein J. Org. Chem. 2021, 17, 2462–2476, doi:10.3762/bjoc.17.163

• the hydrogenation of dihydropyridinones 32 and a following desulfonylation and aromatization to give pyridine derivatives 33 in moderate to good yield. Synthesis of pyrroles via tandem annulation of 1,3-enynes Recently, great achievements have been made in electrophilic iodocyclization of alkynes for

• previous studies on heterocycle synthesis, Punniyamurthy and co-workers designed the electrophilic iodocyclization of 2-nitro-1,3-enynes 34 for the synthesis of pyrrole derivatives. In 2013, they reported an efficient route to pentasubstituted pyrroles from 2-nitro-1,3-enynes 34, amines, and iodine under

• yield. Aliphatic amines were also tolerated, providing the desired products in only moderate yield. The plausible mechanism involves a tandem base-promoted aza-Michael addition, 1,2-iodocyclization, and iodine-mediated oxidative aromatization. In 2017, Zhang and co-workers reported a silver-catalyzed

One-pot preparation of 4-aryl-3-bromocoumarins from 4-aryl-2-propynoic acids with diaryliodonium salts, TBAB, and Na₂S₂O₈

• Teppei Sasaki,
• Katsuhiko Moriyama and
• Hideo Togo

Beilstein J. Org. Chem. 2018, 14, 345–353, doi:10.3762/bjoc.14.22

• 2Aa was obtained in 83% yield at 50 °C (Table 1, entries 11–14). On the other hand, when the present reaction was carried out without CuCl under the same conditions, phenyl ester 2Aa was not obtained at all (Table 1, entry 15). Then, the iodocyclization of phenyl ester 2Aa to 3-iodo-4-phenylcoumarin

• mixture of 1,2-dichloroethane (DCE) and water at 90 °C was carried out to give 3-bromo-4-phenylcoumarin (3Aa) in 68% yield (Table 2, entry 7). When the iodocyclization of phenyl ester 2Aa with tetrabutylammonium iodide (TBAI, 2.0 equiv)/Na2S2O8 (1.5 equiv) was carried out, the yield of iodocyclization

New tricks of well-known aminoazoles in isocyanide-based multicomponent reactions and antibacterial activity of the compounds synthesized

• Maryna V. Murlykina,
• Maryna N. Kornet,
• Sergey M. Desenko,
• Svetlana V. Shishkina,
• Oleg V. Shishkin,
• Aleksander A. Brazhko,
• Vladimir I. Musatov,
• Erik V. Van der Eycken and
• Valentin A. Chebanov

Beilstein J. Org. Chem. 2017, 13, 1050–1063, doi:10.3762/bjoc.13.104

• polyfunctional reagents in Ugi-4CR opens ways to different post-cyclization reactions, thereby broadening the scope. Thus the Ugi-4CR involving substituted propiolic acids, can be followed by electrophilic ipso-iodocyclization [62] or transition-metal-initiated [63][64][65][66][67][68] and metal-free

Symmetry-based approach to oligostilbenoids: Rapid entry to viniferifuran, shoreaphenol, malibatol A, and diptoindonesin G

• Youngeun Jung,
• Dileep Kumar Singh and
• Ikyon Kim

Beilstein J. Org. Chem. 2016, 12, 2689–2693, doi:10.3762/bjoc.12.266

• natural oligostilbenoids guided us to design a modular synthetic approach to these molecules by utilizing a three-step sequence consisting of Sonogashira coupling, iodocyclization, and Suzuki coupling. During our synthesis, the relative reactivities of ester, aldehyde, and alkoxy groups on the same aryl

• . Keywords: anticancer agent; iodocyclization; natural product; oligostilbenoids; Pd-catalyzed coupling; Introduction Oligostilbenoids constitute a family of natural products with various biological functions (Figure 1). Monomeric stilbene units are interconnected in a number of ways to lead to complex

• element [19] of the target molecules. We expected that the key intermediate (inset box of Scheme 1) could be constructed from the monoiodo compounds 1, 2, or 3 through a sequence involving Sonogashira coupling, iodocyclization [20][21][22][23][24][25][26], and Suzuki coupling. As the starting materials (1

A reductive coupling strategy towards ripostatin A

• Kristin D. Schleicher and
• Timothy F. Jamison

Beilstein J. Org. Chem. 2013, 9, 1533–1550, doi:10.3762/bjoc.9.175

• carbonate, performing an iodocyclization, then cleaving the iodocarbonate and closing the epoxide under basic conditions. Silyl protection of the secondary alcohol afforded the desired model compound 28. Enyne 6 and epoxide 28 were subjected to standard nickel-catalyzed reductive coupling conditions, and

• material throughput. In order to proceed with the synthesis, we needed a more robust route, with the following criteria: (1) no protecting groups requiring oxidative cleavage, and (2) introduction of the C13 hydroxy group at an early stage. Iodocyclization approaches to epoxide In the preparation of model

• epoxide 28, iodocyclization was used to introduce oxygenation in a stereoselective fashion from a chiral homoallylic alcohol. Applying this disconnection, we hypothesized that we might be able to introduce the epoxide functional group of 5 by iodocyclization of the tert-butyl carbonate 55 (Figure 6

Study on the total synthesis of velbanamine: Chemoselective dioxygenation of alkenes with PIFA via a stop-and-flow strategy

• Huili Liu,
• Kuan Zheng,
• Xiang Lu,
• Xiaoxia Wang and
• Ran Hong

Beilstein J. Org. Chem. 2013, 9, 983–990, doi:10.3762/bjoc.9.113

• -exo-trig cyclization is the favorable pathway during the PIFA-mediated amide-cyclization of alkene. Two isomers after cyclization were then attributed to the stereoisomers of the C=N double bond in the iminolactone C. This notion is also consistent with numerous reports on the iodocyclization with

When gold can do what iodine cannot do: A critical comparison

• Sara Hummel and
• Stefan F. Kirsch

Beilstein J. Org. Chem. 2011, 7, 847–859, doi:10.3762/bjoc.7.97

• the case with gold-catalyzed cyclizations, the competing elimination through loss of a proton could not be entirely prevented. For example, a methoxyiodocarbocyclization of 27 occurred in 22% yield when the iodocyclization was run in methanol. Additionally, the developing positive charge can be

• cyclizations proceed through gold-carbene intermediates, and the gold in all cases activates the alkyne moiety exclusively. Consequently, most of the gold-catalyzed cyclization modes are not paralleled by iodine-mediated processes. Iodocyclization of 1,6-enynes is known only from very recent examples from

• . Formation of naphthalenes. Formation of indenes. Iodocyclization of 3-silyloxy-1,5-enynes. 5-Endo cyclizations with concomitant nucleophilic trapping. Reactivity of 3-BocO-1,5-enynes. Intramolecular nucleophilic trapping. Approach to azaanthraquinones. Carbocyclizations with enol derivatives. Gold-catalyzed