Dendralene

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A dendralene is a discrete acyclic cross-conjugated polyene.[1][2][3] The simplest dendralene is buta-1,3-diene (1) or [2]dendralene followed by [3]dendralene (2), [4]dendralene (3) and [5]dendralene (4) and so forth. [2]dendralene (butadiene) is the only one not cross-conjugated.

Meet the dendralenes

The name dendralene is pulled together from the words dendrimer, linear and alkene. The higher dendralenes are of scientific interest because they open up a large array of new organic compounds from a relatively simple precursor especially by Diels-Alder chemistry. Their cyclic counterparts are aptly called radialenes.

Synthesis

Vinylbutadiene ([3]dendralene) was first prepared in 1955 by pyrolysis of a triacetate:[4][5]

Vinyl butadiene synthesis Baily 1955

This compound reacts with two equivalents of maleic anhydride in a tandem DA reaction:[6]

Reaction vinylbutadiene maleic anhydride

With benzoquinone the reaction product was a linear polymer.

Several syntheses of substituted [3]dendralenes have been reported, one via an allene,[7] one via a Horner–Wadsworth–Emmons reaction,[8] one via a cross-coupling reaction[9] and one from an allylic carbonate.[10]

One synthetic route to [4]dendralene starts from chloroprene.[11] This compound is converted to a Grignard reagent by action of magnesium metal which is then reacted with copper(I) chloride to an organocopper intermediate which is in turn dimerized using copper(II) chloride in an oxidative coupling reaction to give the butadiene dimer called [4]dendralene.

[4]dendralene synthetic scheme from chloroprene

The gas-phase molecular structure of [4]dendralene has been reported [12]

The [8]-dendralene compound was reported in 2009:[13]

[8]-dendralene synthesis

in a successive Kumada–Tamao–Corriu coupling and Negishi coupling.

A series of [9] to [12]-dendralenes has been reported in 2016 [14]

Properties

Even-membered dendralenes (e.g. [6]dendralene, [8]dendralene) tend to behave as chains of decoupled and isolated diene units. The ultraviolet absorption maxima equal that of butadiene itself. The dendralenes with an odd number of alkene units are more reactive due to the presence of favorable s-cis diene conformations and Diels-Alder reactions take place more easily with a preference for the termini.

Reactions

With simple dienophiles, dendralenes can give quick access to complex molecules in Diels-Alder reactions. Several reaction schemes have been reported [11][15][16][17][18][19][20][21][22]

[4]dendralene shows a tandem Diels-Alder reaction with the dienophile N-methyl-maleimide (NMM).[11] Complete site selectivity is possible with the addition of the Lewis acid methyldichloroaluminium. With one set of premixing and 2 equivalents of NMM, the central diene group is targeted to the monoadduct 3. With another set and a larger amount of dienophile, the terminal groups react and the reaction proceeds from the monoadduct to the trisadducts 2 and 2b.

dendralene Diels-Alder reaction

One reaction variation is cyclopropanation to a compound class called ivyanes with a reported synthesis in a Simmons–Smith reaction (diethyl zinc / trifluoroacetic acid) of the first 6 members.[23] These 1,1-oligocyclopropanes are stable (except when exposed to acids) and have a large heat of combustion with [6]ivyane exceeding that of cubane. The oligocyclopropane chains adopt a helical conformation. For [3]dendralene a photochemical cyclisation reaction has been reported [24]

Derivatives

A bicyclic [4]dendralene compound has been reported.[25]

References

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  1. ↑ Henning Hopf, Classics in Hydrocarbon Chemistry, Wiley VCH, 2000.
  2. ↑ Script error: No such module "Citation/CS1".
  3. ↑ Preparation and Synthetic Value of π-Bond-Rich Branched Hydrocarbons Michael S. Sherburn Accounts of Chemical Research 2015 48 (7), 1961-1970 Script error: No such module "CS1 identifiers".
  4. ↑ Script error: No such module "Citation/CS1".
  5. ↑ Script error: No such module "Citation/CS1".
  6. ↑ Script error: No such module "Citation/CS1".
  7. ↑ Mieko Arisawa, Takumichi Sugihara and Masahiko Yamaguchi Synthesis of cross-conjugated trienes by dimerization of allenes with palladium-phenol catalyst Chem. Commun. 1998; 2615-2616 Script error: No such module "CS1 identifiers".
  8. ↑ Rekha Singh and Sunil K. Ghosh Synthesis of substituted [3]dendralenes and their unique cycloaddition reactions Chem. Commun. 2011; Advance Article Script error: No such module "CS1 identifiers".
  9. ↑ Script error: No such module "Citation/CS1".
  10. ↑ Kassem Beydoun, Hui-Jun Zhang, Basker Sundararaju, Bernard Demerseman, Mathieu Achard, Zhenfeng Xi and Christian Bruneau Efficient ruthenium-catalyzed synthesis of [3]dendralenes from 1,3-dienic allylic carbonates Chem. Commun. 2009; 6580-6582 Script error: No such module "CS1 identifiers".
  11. ↑ a b c Script error: No such module "Citation/CS1".
  12. ↑ Molecular Structure of 3,4-Dimethylenehexa-1,5-diene ([4]Dendralene), C8H10, in the Gas Phase As Determined by Electron Diffraction and ab Initio Calculations Paul T. Brain,Bruce A. Smart,Heather E. Robertson,Martin J. Davis,†, David W. H. Rankin,*, William J. Henry, and Ian Gosney The Journal of Organic Chemistry 1997 62 (9), 2767-2773 Script error: No such module "CS1 identifiers".
  13. ↑ Practical Synthesis of the Dendralene Family Reveals Alternation in Behavior Alan D. Payne, Gomotsang Bojase, Michael N. Paddon-Row, and Michael S. Sherburn Angew. Chem. Int. Ed. 2009, 48, Script error: No such module "CS1 identifiers".
  14. ↑ Discovery and Computational Rationalization of Diminishing Alternation in [n]Dendralenes Mehmet F. Saglam, Thomas Fallon, Michael N. Paddon-Row, and Michael S. Sherburn Journal of the American Chemical Society 2016 138 (3), 1022-1032 Script error: No such module "CS1 identifiers".
  15. ↑ Script error: No such module "Citation/CS1".
  16. ↑ Script error: No such module "Citation/CS1".
  17. ↑ A novel and facile stereocontrolled synthetic method for polyhydro-quinolines and pyridopyridazines via a diene-transmissive Diels–Alder reaction involving inverse electron-demand hetero Diels–Alder cycloaddition of cross-conjugated azatrienes Tetrahedron, Volume 64, Issue 41, 6 October 2008, Pages 9705-9716 Satoru Kobayashi, Tomoki Furuya, Takashi Otani and Takao Saito Script error: No such module "CS1 identifiers".
  18. ↑ Synthesis of a Potent Antimalarial Amphilectene Sergey V. Pronin and Ryan A. Shenvi Journal of the American Chemical Society 2012 134 (48), 19604-19606 Script error: No such module "CS1 identifiers".
  19. ↑ Script error: No such module "Citation/CS1".
  20. ↑ Practical Synthesis and Reactivity of [3]Dendralene Tanya A. Bradford, Alan D. Payne, Anthony C. Willis, Michael N. Paddon-Row, and Michael S. Sherburn The Journal of Organic Chemistry 2010 75 (2), 491-494 Script error: No such module "CS1 identifiers".
  21. ↑ Multicomponent Diene-Transmissive Diels–Alder Sequences Featuring Aminodendralenes S. M. Tan, A. C. Willis, M. N. Paddon-Row, M. S. Sherburn, Angew. Chem. Int. Ed. 2016, 55, 3081. Script error: No such module "CS1 identifiers".
  22. ↑ Synthesis and Diels–Alder Reactivity of Substituted [4]Dendralenes Mehmet F. Saglam, Ali R. Alborzi, Alan D. Payne, Anthony C. Willis, Michael N. Paddon-Row, and Michael S. Sherburn The Journal of Organic Chemistry 2016 81 (4), 1461-1475 Script error: No such module "CS1 identifiers".
  23. ↑ Script error: No such module "Citation/CS1".
  24. ↑ Tetrahedron Letters Volume 35, Issue 29, 18 July 1994, Pages 5251–5252 A novel photochemical reaction of [3]dendralene derivatives Keiji Okada, Katsuji Maehara, Masaji Oda Script error: No such module "CS1 identifiers".
  25. ↑ Transformation of azulenes to bicyclic [4]dendralene and heptafulvene derivatives via photochemical cycloaddition of dialkylsilylene Tomoyuki Kosai, Shintaro Ishida ,Takeaki Iwamoto Chem. Commun., 2015,51, 10707-10709 Script error: No such module "CS1 identifiers".

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