Sumanene is a polycyclic aromatic hydrocarbon and of scientific interest because the molecule can be considered a fragment of buckminsterfullerene. Suman means "sunflower" in both Hindi and Sanskrit.[1] The core of the arene is a benzene ring and the periphery consists of alternating benzene rings (3) and cyclopentadiene rings (3). Unlike fullerene, sumanene has benzyl positions which are available for organic reactions.
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Preferred IUPAC name
4,7-Dihydro-1H-tricyclopenta[def,jkl,pqr]triphenylene | |
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Properties | |
C21H12 | |
Molar mass | 264.32 |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references
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The structure of Sumanene can be inferred from oxidation of 1,5,9-trimethyltriphenylene but the first practical synthesis starts from norbornadiene.[2] Norbornadiene is converted into a stannane by action of n-butyllithium, dibromoethane and tributyltinchloride. An Ullmann reaction of this stannane with CuTC affords the benzene core. The methylene bridges (-CH
2-) created in this conversion then migrate in a tandem ring-opening metathesis and ring-closing metathesis by the Grubbs' catalyst. The final structure is obtained by oxidation by DDQ.
Sumanene is a bowl-shaped molecule with a bowl depth of 118 picometers.[3] The 6 hub carbon atoms are pyramidalized by 9° and the molecule displays considerable bond alternation (138.1 to 143.1 pm). Sumanene also experiences bowl-to-bowl inversion with an inversion barrier of 19.6 kcal/mol (82 kJ/mol) at 140 °C which is much higher than that found for its corannulene cousin. Like any benzylic proton, the sumanene protons can be abstracted by a strong base such as t-butyl lithium to form the sumanene mono carbanion. This strong nucleophile can react with an electrophile such as trimethylsilyl chloride to the trimethylsilyl derivative.
The trianion has also been reported.[4] Electron transport properties have been investigated [5][6] as well as carbon NMR[7]
Sumanene derivatives [8] such as naphtosumanene [9] and trisialsumanene [10][11] have been described. Chiral sumanenes are of some interest with respect to inherent chirality,[12] examples are chiral trimethylsumanene [13] and a chiral sumanene cyclopentadienyl iron complex [14]