Highly congested derivatives of biphenyl were prepared by double Diels‐Alder reactions of cyclopentadienones with substituted butadiynes. The reaction of 2,3,5‐tri(
Tetradecaphenyl‐
- Award ID(s):
- 1762452
- NSF-PAR ID:
- 10446024
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Chemistry – A European Journal
- Volume:
- 28
- Issue:
- 41
- ISSN:
- 0947-6539
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract tert ‐butyl)cyclopentadienone (5 ) and diphenylbutadiyne (3 ) gave only the single adduct, 1‐(phenylethynyl)‐2‐phenyl‐3,5,6‐tri‐tert ‐butylbenzene (6 ), and even extreme conditions gave no second addition. When tetracyclone (4 ) was added to bis(trimethylsilyl)butadiyne (8 ), two additions were achieved, but one silyl group was lost either during, or immediately following, the second addition to give 2‐(trimethylsilyl)‐2′,3,3′,4,4′,5,5′,6‐octaphenylbiphenyl (11 ). However, when 3,4‐diphenyl‐2,5‐dimethylcyclopentadienone (12 ) was added to8 , the fully substituted 2,2′‐bis(trimethylsilyl)‐4,4′,5,5′‐tetraphenyl‐3,3′,6,6′‐tetramethylbiphenyl (14 ) was formed. The X‐ray structures of compounds11 and14 show them to be quite crowded, but the central biphenyl rings do not exhibit the distortions previously observed in decaphenylbiphenyl. In an alternative approach, arynes were added to 5,5′‐bis(4‐chlorophenyl)‐3,3′,4,4′‐tetraphenyl‐2,2′‐bis(cyclopentadienone) (18 ). Simple benzyne added twice to give 4,4′‐bis(4‐chlorophenyl)‐2,2′,3,3′‐tetraphenyl‐1,1′‐binaphthyl (19 ) in low yield, but tetraphenylbenzyne, generated from tetraphenylanthranilic acid, added only once. -
Treatment of Mn(N(SiMe3)2)2(THF)2 with bulky chelating bis(alkoxide) ligand [1,1′:4′,1′′-terphenyl]-2,2′′-diylbis(diphenylmethanol) (H2[O-terphenyl-O]Ph) formed a seesaw manganese(II) complex Mn[O-terphenyl-O]Ph(THF)2, characterized by structural, spectroscopic, magnetic, and analytical methods. The reactivity of Mn[O-terphenyl-O]Ph(THF)2 with various nitrene precursors was investigated. No reaction was observed between Mn[O-terphenyl-O]Ph(THF)2 and aryl azides. In contrast, the treatment of Mn[O-terphenyl-O]Ph(THF)2 with iminoiodinane PhINTs (Ts = p-toluenesulfonyl) was consistent with the formation of a metal-nitrene complex. In the presence of styrene, the reaction led to the formation of aziridine. Combining varying ratios of styrene and PhINTs in different solvents with 10 mol% of Mn[O-terphenyl-O]Ph(THF)2 at room temperature produced 2-phenylaziridine in up to a 79% yield. Exploration of the reactivity of Mn[O-terphenyl-O]Ph(THF)2 with various olefins revealed (1) moderate aziridination yields for p-substituted styrenes, irrespective of the electronic nature of the substituent; (2) moderate yield for 1,1′-disubstituted α-methylstyrene; (3) no aziridination for aliphatic α-olefins; (4) complex product mixtures for the β-substituted styrenes. DFT calculations suggest that iminoiodinane is oxidatively added upon binding to Mn, and the resulting formal imido intermediate has a high-spin Mn(III) center antiferromagnetically coupled to an imidyl radical. This imidyl radical reacts with styrene to form a sextet intermediate that readily reductively eliminates the formation of a sextet Mn(II) aziridine complex.more » « less
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1,3-Dimethyl-2,3-dihydrobenzo[
d ]imidazoles,1H , and 1,1',3,3'-tetramethyl-2,2',3,3'-tetrahydro-2,2'-bibenzo[d ]imidazoles,1 2 , are of interest as n-dopants for organic electron-transport materials. Salts of 2-(4-(dimethylamino)phenyl)-4,7-dimethoxy-, 2-cyclohexyl-4,7-dimethoxy-, and 2-(5-(dimethylamino)thiophen-2-yl)benzo[d ]imidazolium (1g–i + , respectively) have been synthesized and reduced with NaBH4to1gH ,1hH , and1iH , and with Na:Hg to1g 2 and1h 2 . Their electrochemistry and reactivity were compared to those derived from 2-(4-(dimethylamino)phenyl)- (1b + ) and 2-cyclohexylbenzo[d ]imidazolium (1e + ) salts.E (1 + /1 • ) values for 2-aryl species are less reducing than for 2-alkyl analogues, i.e., the radicals are stabilized more by aryl groups than the cations, while 4,7-dimethoxy substitution leads to more reducingE (1 + /1 • ) values, as well as cathodic shifts inE (1 2 •+ /1 2 ) andE (1H •+ /1H ) values. Both the use of 3,4-dimethoxy and 2-aryl substituents accelerates the reaction of the1H species with PC61BM. Because 2-aryl groups stabilize radicals,1b 2 and1g 2 exhibit weaker bonds than1e 2 and1h 2 and thus react with 6,13-bis(triisopropylsilylethynyl)pentacene (VII ) via a “cleavage-first” pathway, while1e 2 and1h 2 react only via “electron-transfer-first”.1h 2 exhibits the most cathodicE (1 2 •+ /1 2 ) value of the dimers considered here and, therefore, reacts more rapidly than any of the other dimers withVII via “electron-transfer-first”. Crystal structures show rather long central C–C bonds for1b 2 (1.5899(11) and 1.6194(8) Å) and1h 2 (1.6299(13) Å). -
A new sterically bulky chelating bis(alkoxide) ligand 3,3′-([1,1′:4′,1′′-terphenyl]-2,2′′-diyl)bis(2,2,4,4-tetramethylpentan-3-ol), (H 2 [OO] tBu ), was prepared in a two-step process as the dichloromethane monosolvate, C 36 H 50 O 2 ·CH 2 Cl 2 . The first step is a Suzuki–Miyaura coupling reaction between 2-bromophenylboronic acid and 1,4-diiodobenzene. The resulting 2,2′′-dibromo-1,1′:4′,1′′-terphenyl was reacted with t BuLi and hexamethylacetone to obtain the desired product. The crystal structure of H 2 [OO] tBu revealed an anti conformation of the [CPh 2 (OH)] fragments relative to the central phenyl. Furthermore, the hydroxyl groups point away from each other. Likely because of this anti – anti conformation, the attempts to synthesize first-row transition-metal complexes with H 2 [OO] tBu were not successful.more » « less
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Abstract 3,3′,5,5′‐Tetra‐
tert ‐butyl‐2′‐sulfanyl[1,1′‐biphenyl]‐2‐ol (H2[t Bu4OS]) was prepared in 24 % yield overall from the analogous biphenol using standard techniques. Addition of H2[t Bu4OS] to Mo(NAr)(CHCMe2Ph)(2,5‐dimethylpyrrolide)2led to formation of Mo(NAr)(CHCMe2Ph)[t Bu4OS], which was trapped with PMe3to give Mo(NAr)(CHCMe2Ph)[t Bu4OS](PMe3) (1 (PMe3)). An X‐ray crystallographic study of1 (PMe3) revealed that two structurally distinct square pyramidal molecules are present in which the alkylidene ligand occupies the apical position in each. Both1 (PMe3)Aand1 (PMe3)Bare disordered. Mo(NAd)(CHCMe2Ph)(t Bu4OS)(PMe3) (2 (PMe3); Ad=1‐adamantyl) and W(NAr)(CHCMe2Ph)(t Bu4OS)(PMe3) (3 (PMe3)) were prepared using analogous approaches.1 (PMe3) reacts with ethylene (1 atm) in benzene within 45 minutes to give an ethylene complex Mo(NAr)(t Bu4OS)(C2H4) (4 ) that is isolable and relatively stable toward loss of ethylene below 60 °C. An X‐ray study shows that the bond distances and angles for the ethylene ligand in4 are like those found for bisalkoxide ethylene complexes of the same general type. Complex1 (PMe3) in the presence of one equivalent of B(C6F5)3catalyzes the homocoupling of 1‐decene, allyltrimethylsilane, and allylboronic acid pinacol ester at ambient temperature.1 (PMe3),2 (PMe3), and3 (PMe3) all catalyze the ROMP ofrac ‐endo ,exo ‐5,6‐dicarbomethoxynorbornene (rac ‐DCMNBE) in the presence of B(C6F5)3, but the polyDCMNBE that is formed has a random structure.
