Chelation-Controlled Bergman Cyclization:  Synthesis and Reactivity of Enediynyl Ligands

Basak, Amit; Mandal, Saptarshi; Bag, Subhendu Sekhar

doi:10.1021/cr020069k

Cited by 184 publications

(64 citation statements)

References 128 publications

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“…The genesis of synthetic routes to simple metal-alkynes has made possible the preparation of metal-polyynes (18) that perform unimolecular electron transfer, form metallomesogens (19), and structures possessing nonlinear optical properties (19)(20)(21)(22)(23)(24). More recently, the preparation of s and p metal-enediyne complexes has emerged as a metal-mediated route to traditional organic Bergman cyclization (25)(26)(27). Once again, the confluence of metal and alkyne geometric and electronic structure is the enabling feature that translates into new chemical properties and reactivities, further evolving the already diverse world of metal-alkyne chemistry.…”

Section: A Backgroundmentioning

confidence: 99%

“…Coordination chemistry approaches to enediyne cyclization have been shown to be extremely dependent on the conformation of the bound enediyne ligand, which is strongly influenced by the geometry of the resulting transition metal coordination complex (25)(26)(27). The first proposals suggesting metal coordination could influence the conformation of the bound enediyne ligand were reported in 1995-1996 by Buchwald and co-workers (544) and König et al (545,546).…”

Section: Geometric Factors Influencing Bergman Cyclizationmentioning

confidence: 99%

“…A three-component tandem metathesis/Diels-Alder reaction promoted by second generation Grubbs' catalyst to form functionalized tricycles. in organometallic and inorganic chemistry have been recently published(25)(26)(27) and serve as supplementary reference material. This section focuses on only metal-mediated cyclization strategies.1.…”

mentioning

confidence: 99%

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Unique Metal‐Diyne, ‐Enyne, and ‐Enediyne Complexes: Part of the Remarkably Diverse World of Metal‐Alkyne Chemistry

Bhattacharyya

Sangita

Zaleski

2007

Progress in Inorganic Chemistry

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Section: A Backgroundmentioning

confidence: 99%

Section: Geometric Factors Influencing Bergman Cyclizationmentioning

confidence: 99%

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Unique Metal‐Diyne, ‐Enyne, and ‐Enediyne Complexes: Part of the Remarkably Diverse World of Metal‐Alkyne Chemistry

Bhattacharyya

Sangita

Zaleski

2007

Progress in Inorganic Chemistry

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“…First discovered in late 1980's, these compounds captured immediate attention of the chemists and biologists throughout the world due their complex molecular framework and novel biological activity profile [6]. All the natural enediynes such as calicheamicin [7], esperamicin [8], dynamicin [9,10] maduroptin [1], and more recently uncialamycin [11] possess highly strained enediyne unit, a triggering device and delivery agent and under biological conditions these compounds forms diradical which is responsible for their anticancer activity [12,13].…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Anticancer Activity of 13‐Membered Cyclic Enediynes

Sharma

Joshi

Kumar

et al. 2011

Archiv der Pharmazie

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We herein describe the synthesis of 15 novel 13-membered cyclic enediyne derivatives using simple and straightforward approach. Representative examples were screened for their anticancer activities on 60 different human tumor cell lines representing various histologies viz. leukemia, melanoma, and cancers of lung, colon, kidney, ovary, breast, prostate, and central nervous system. The enediyne derivatives with halogen substitutions, especially fluorides were found to be active against most of the cell lines. The initial results indicates marginal to good inhibition for the growth of tumor cells for several cell lines, which shows the potential of these class of compound towards anticancer application.

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“…The activity profiles of the well-known, medicinally important enediynes are greatly perturbed by weak interactions. [11] Jones et al [12] have shown that strong electron-withdrawing groups increase the barrier for Bergman cyclization, while σ-donating groups decrease it; π-conjugation, in particular donation, has little effect. In a recent paper Alabugin [13] evaluated the stereoelectronic effects in cyclohexane-, 1,3-dioxane-, 1,3-oxathiane-, and 1,3-dithiane-or donor/donor combinations relative to the acceptor/acceptor pair.…”

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confidence: 99%

The Effect of Charge‐Transfer Complexation/π‐Stacking Interactions in Lowering the Activation Barrier of the Bergman Cyclization

2005

Self Cite

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To elaborate the concept of weak interactions and their effect on Bergman Cyclization (BC), several 1,2-dikynyl benzenes incorporating various combinations of donor and acceptor units in the two arms of the enediynes were designed and synthesized, and their charge-transfer interactions followed by UV/Vis spectroscopy. The thermal reactivities, as studied by DSC, show an increase in reactivity for the donor/acceptor More than fifty years ago, Mulliken [1] suggested that charge-transfer (CT) complexes "may afford new possibilities for understanding intermolecular interactions in biological systems". This statement proved to be true after several biochemical phenomena were explained on the basis of CT complex formation. [2][3][4][5] CT complexes arising from the interaction of aromatic π-donor and -acceptor molecules have been studied extensively. However, fewer intramolecular CT analogs have been reported, primarily of the cyclophane type, in which the donor and acceptor portions are locked together in a rather rigid arrangement.[6] More flexible intramolecular CT complexes have been reported in a recent communication, whereby a cyclohexane skeleton is substituted at adjacent trans positions with aromatic donor and acceptor groups.[7] Besides charge-transfer interactions, attractive, nonbonding interactions between aromatic units (π-stacking) play a central role in many areas of chemistry and biochemistry, the most notable ones being in molecular recognition and self-assembly, [8] in base-pair stacking in DNA, [9] and in controlling the tertiary structure of proteins, [10] and hence are of interest to all realms of chemistry and biology. The activity profiles of the well-known, medicinally important enediynes are greatly perturbed by weak interactions.[11] Jones et al. [12] have shown that strong electron-withdrawing groups increase the barrier for Bergman cyclization, while σ-donating groups decrease it; π-conjugation, in particular donation, has little effect. In a recent paper Alabugin [13] evaluated the stereoelectronic effects in cyclohexane-, 1,3-dioxane-, 1,3-oxathiane-, and 1,3-dithiane- [ based enediynes. Zaleski et al. [14] have shown how dramatically the steric influences of the functional groups at the termini of acyclic enediynes can affect the Bergman cyclization (BC) temperatures of the resulting compounds. In this communication, we wish to describe, for the first time, the synthesis and characterization of a series of donor-acceptor (D/A) containing 1,2-dialkynylbenzenes (Figure 1) and the effect of CT complexation and π-π interactions on the kinetics of the BC. The corresponding D/D and A/A counterparts were also synthesized to compare the reactivities towards BC. Incidentally, aromatic 1,2-dialkynyl systems have been considered in the literature [15] to be a variant of Figure 1. Representation of donor-acceptor-containing enediynyl compounds.

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Chelation-Controlled Bergman Cyclization: Synthesis and Reactivity of Enediynyl Ligands

Cited by 184 publications

References 128 publications

Unique Metal‐Diyne, ‐Enyne, and ‐Enediyne Complexes: Part of the Remarkably Diverse World of Metal‐Alkyne Chemistry

Unique Metal‐Diyne, ‐Enyne, and ‐Enediyne Complexes: Part of the Remarkably Diverse World of Metal‐Alkyne Chemistry

Synthesis and Anticancer Activity of 13‐Membered Cyclic Enediynes

The Effect of Charge‐Transfer Complexation/π‐Stacking Interactions in Lowering the Activation Barrier of the Bergman Cyclization

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