Reductive Bergman-Type Cyclizations of Cross-Conjugated Enediynes to Fulvene and Fulvalene Anions:  The Role of the Substituent

Treitel, Noach; Eshdat, Lior; Sheradsky, Tuvia; Donovan, Patrick; Tykwinski, Rik R.; Scott, Lawrence T.; Hopf, Henning; Rabinovitz, Mordecai

doi:10.1021/ja0566477

Cited by 29 publications

(11 citation statements)

References 37 publications

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“…Application of these principles led to Bergman-like cyclizations of 3-substituted 1,4-pentadiynes, 58 Myers-Saito reactions leading to hetero-cyclopentadiendiyl derivatives, 59 the cyclization of Moore's enynes-ketenes to oxo-heterocyclopentadiendiyl, 60 and diallenes to hetero-3,4-dimethylenecyclopentadienediyl derivatives. 57 True predictions were made and it is encouraging to see that some were proven experimentally in the meantime, 61,62 as well as the formation of anions of fulvenes and fulvalene derivatives from cross-conjugated enediynes. 62 The enlargement of the heuristic concept to heteroatom-systems increased the number of possible reactions that exhibit comparable properties, and that might be of interest for synthetic chemistry or for studies investigating their DNA cleavage abilities.…”

Section: A Case Study: Pericyclic Reactions-the Six Electron Casementioning

confidence: 89%

“…57 True predictions were made and it is encouraging to see that some were proven experimentally in the meantime, 61,62 as well as the formation of anions of fulvenes and fulvalene derivatives from cross-conjugated enediynes. 62 The enlargement of the heuristic concept to heteroatom-systems increased the number of possible reactions that exhibit comparable properties, and that might be of interest for synthetic chemistry or for studies investigating their DNA cleavage abilities.…”

Section: A Case Study: Pericyclic Reactions-the Six Electron Casementioning

confidence: 89%

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Heuristic thinking makes a chemist smart

2010

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We focus on the virtually neglected use of heuristic principles in understanding and teaching of organic chemistry. As human thinking is not comparable to computer systems employing factual knowledge and algorithms--people rarely make decisions through careful considerations of every possible event and its probability, risks or usefulness--research in science and teaching must include psychological aspects of the human decision making processes. Intuitive analogical and associative reasoning and the ability to categorize unexpected findings typically demonstrated by experienced chemists should be made accessible to young learners through heuristic concepts. The psychology of cognition defines heuristics as strategies that guide human problem-solving and deciding procedures, for example with patterns, analogies, or prototypes. Since research in the field of artificial intelligence and current studies in the psychology of cognition have provided evidence for the usefulness of heuristics in discovery, the status of heuristics has grown into something useful and teachable. In this tutorial review, we present a heuristic analysis of a familiar fundamental process in organic chemistry--the cyclic six-electron case, and we show that this approach leads to a more conceptual insight in understanding, as well as in teaching and learning.

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Section: A Case Study: Pericyclic Reactions-the Six Electron Casementioning

confidence: 89%

Section: A Case Study: Pericyclic Reactions-the Six Electron Casementioning

confidence: 89%

Heuristic thinking makes a chemist smart

2010

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“…[11] Eine alternative Syntheseroute, im letzten Jahrzehnt untersucht, erzeugt Dibenzopentafulvalene 1 über eine reduktive Bergman-artige Cyclisierung von kreuzkonjugierten Endiinen 2 (Schema 1, oben). [12] Carbopalladierungen sind vielseitige Verfahren zur Erzeugung hochsubstituierter oligocyclischer Systeme. In den letzten zwei Jahrzehnten wurde eine Vielzahl von DominoCarbopalladierungssequenzen entwickelt, welche zu homound heterocyclischen Systemen wie Lactonen, Chromanen, molekularen Schaltern und weiteren komplexen Produkten in einem einzigen Schritt ausgehend von verhältnismäßig einfachen Startmaterialien führten.…”

Section: Im Gedenken An Michael Bendikovunclassified

Ein Dominoprozess zu Dibenzopentafulvalenen mittels vierfacher Carbopalladierung

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“…[11] An alternative synthetic pathway investigated in the last decade accesses dibenzopentafulvalenes 1 by reductive Bergman-type cyclizations of cross-conjugated enediynes 2 (Scheme 1, top). [12] Highly substituted unsaturated oligocyclic systems can also be prepared by carbopalladation reactions. In the last two decades a number of domino carbopalladation sequences have been developed, yielding homo-and heterocyclic systems such as lactones, chromanes, molecular switches, and further complex systems in one single step from relatively simple starting materials.…”

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confidence: 99%

A Domino Approach to Dibenzopentafulvalenes by Quadruple Carbopalladation

2013

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Owing to their special electronic properties cross-conjugated systems have experienced a renaissance in recent years, [1] and also pentafulvalene and its substituted analogues have come back into focus. [2,3] Originally regarded as laboratory curiosities displaying nonplanar structures and unusual bond lengths and angles, [4] they have attracted attention as ligands [5] for transition metals and as two-electron acceptors affording aromatic dianions. [6] Whereas the parent fulvalene is unstable at temperatures above À78 8C, [7] the perchloro derivative shows completely reversible redox behavior. [6b] Further investigations with fulvalene vinylogues [6b] indicate properties conducive to tuning the performance of organic-based batteries on a molecular level.The preparation of symmetrical pentafulvalenes has been realized for the most part by the coupling of two cyclopentadienyl rings, involving strong lithium bases and often molecular oxygen as the oxidant or CuCl 2 as the coupling promoter. [7,8] Other couplings have been performed by the Grignard addition to ketones [9] and homo couplings employing halogenated species and transition metals. [10] Also diazo compounds, which readily release nitrogen, have served as starting materials. [11] An alternative synthetic pathway investigated in the last decade accesses dibenzopentafulvalenes 1 by reductive Bergman-type cyclizations of cross-conjugated enediynes 2 (Scheme 1, top). [12] Highly substituted unsaturated oligocyclic systems can also be prepared by carbopalladation reactions. In the last two decades a number of domino carbopalladation sequences have been developed, yielding homo-and heterocyclic systems such as lactones, chromanes, molecular switches, and further complex systems in one single step from relatively simple starting materials. [13][14][15] Herein we disclose a novel dibenzopentafulvalene synthesis which affords the pentafulvalene framework in only one step through a quadruple carbopalladation process. Our retrosynthetic strategy relied on a readily available biphenylacetylene and two tethered alkyne moieties 4 (Scheme 1, bottom). We envisioned that a sequence starting with the oxidative addition of Pd into the CÀBr bond followed by three carbopalladation steps to the CÀC triple bonds and finishing with a final carbopalladation to the newly formed alkene would provide the dibenzopentafulvalene skeleton 3.To test our approach, we chose the biphenyl derivative 7 which was coupled with various diynes (Scheme 2). Biphenyl 7 was synthesized in two steps by the Suzuki-Miyaura coupling of the trisubstituted arene 5 and boronic acid 6 followed by removal of the silyl protecting groups in 75 % overall yield. Various diynes were obtained by Sonogashira cross-coupling of terminal diyne 8; the respective alcohols were transformed by Appel reaction into propargylic iodides 9. Final nucleophilic substitution of 9 by the phenolic hydroxy group in 7 afforded the domino substrates 4 in good to excellent yields.We initially chose substrate 4 a to optimize the rea...

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Reductive Bergman-Type Cyclizations of Cross-Conjugated Enediynes to Fulvene and Fulvalene Anions: The Role of the Substituent

Cited by 29 publications

References 37 publications

Heuristic thinking makes a chemist smart

Heuristic thinking makes a chemist smart

Ein Dominoprozess zu Dibenzopentafulvalenen mittels vierfacher Carbopalladierung

A Domino Approach to Dibenzopentafulvalenes by Quadruple Carbopalladation

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