The Pursuit of Perphenylterphenyls

Abstract

Tetradecaphenyl-p-terphenyl (2) was synthesized from 2,3,5,6-tetraphenyl-1,4-diiodobenzene (11) by two methods. Ullmann coupling of 11 with pentaphenyliodobenzene (9) gave compound 2 in 1.7 % yield, and Sonogashira coupling of 11 with phenylacetylene, followed by a double Diels-Alder reaction of the product diyne 12 with tetracyclone (6), gave 2 in 1.5 % overall yield. The latter reaction also gave the monoaddition product 4-(phenylethynyl)-2,2 ',3,3',4',5,5',6,6'-nonaphenylbiphenyl (13) in 4 % overall yield. The X-ray structures of compounds 2 and 13 show them to possess core aromatic rings distorted into shallow boat conformations. Density functional calculations indicate that these unusual structures are not the lowest energy conformations in the gas phase and may be the result of packing forces in the crystal. In addition, while uncorrected DFT calculations indicate that the strain energy in compound 2 is approximately 50 kcal/mol, dispersion-corrected DFT calculations suggest that it is essentially unstrained, due to compensating, favorable, intramolecular interactions of its many phenyl rings. An attempted synthesis of tetradecaphenyl-o-terphenyl (4) by reaction of diphenylhexatriyne ( 14) with three equivalents of tetracyclone at 350 °C gave only the diadduct 2-(phenylethynyl)-2 ',3,3',4,4',5,5',6,6'-nonaphenylbiphenyl (15) in 17 % yield. Even higher temperatures failed to produce 4 and lowered the yield of 15, perhaps due to rapid decomposition of the starting materials. Ullmann coupling of 3,4,5,6-tetraphenyl-1,2-diiodobenzene ( 16) and compound 9 also failed to give compound 4.

How great is the stabilization of crowded polyphenylbiphenyls by London dispersion?

“…Generally, continuum solvent models have little effect on the relative energies of hydrocarbon conformations and transition states. 4,38 We have confirmed this by calculating the relative energies of the D 2 and C 1 conformations in benzene, using a polarizable continuum solvent model. The results are presented is the ESI† and clearly illustrate the small effect of including a continuum solvent model.…”

“…Perphenyl arenes are sterically congested aromatic hydrocarbons whose molecular structure and stability challenge common perceptions in Chemistry. [1][2][3][4][5][6][7][8] These crowded molecules often release congestion by distortion from planarity, adopting twisted and chiral molecular geometries. That is the case, for example, for decaphenylanthracene, 6 decaphenylphenanthrene, 7 and dodecaphenyltetracene.…”

A fruitful century for the scalable synthesis and reactions of biphenyl derivatives: applications and biological aspects

“…As aromatic polyphenyl scaffolds give a crowded molecule that usually relieves the congestion by distortion from planarity displaying highly reversible electrochemical properties as this merit shared by a few organic compounds. 86 Whereas, a mixture of four different polycyclic products 52–55 were furnished by reaction of 2,2′-diiodo-biphenyl 50 with (1 H -inden-2-yl)boronic acid ( 51 ) in the presence of palladium catalyst [Pd(PPh 3 ) 4 ] and K 3 PO 4 in refluxing DME/H 2 O (Scheme 25). 85…”

“…As aromatic polyphenyl scaffolds give a crowded molecule that usually relieves the congestion by distortion from planarity displaying highly reversible electrochemical properties as this merit shared by a few organic compounds. 86 Therefore, a proposed mechanism for the formation of 1Hinden-1′,3′-dihydrospiro[uorene-9,2′-indene] 52 is depicted in Scheme 26. Initially, a palladium catalyst is inserted between C-I bond, then (1H-inden-2-yl) boronic acid ( 51) is coupled with (2′-iodo-[1,1′-biphenyl]-2-yl) palladium(II)iodide (52A), followed by intramolecular Heck reaction from 52B to 52C.…”

“…Then, a quick addition of 1,2-dibromoethane (EDB) was added to afford 2-bromoethyl-1,1′-biphenyl 84. 106 A mixture of biphenyl ( 2 Moreover, treatment of biphenyl (2) with cyclopentene (86) in the presence of AlCl 3 and DCE at 0 °C for 24 h afforded 4cyclopentyl-1,1′-biphenyl (87). 107 Additionally, using trichloromethane (CHCl 3 ) instead of DCE at 20 °C for 10 h led to formation of 4,4′-dicyclopentyl-1,1′-biphenyl (88) (Scheme 37).…”