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Abstract Highly congested derivatives of biphenyl were prepared by double Diels‐Alder reactions of cyclopentadienones with substituted butadiynes. The reaction of 2,3,5‐tri(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 compounds11and14show 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.
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On the road to stable, isolable [4]cumulenes: Reactivity and cyclization reactions
Abstract The design and synthesis of persistent tetraaryl[4]cumulenes are reported. Derivatives with phenyl endgroups ([4]Phand[4]Ph/Ar*) are susceptible to reactions during synthesis and/or purification that complicate isolation of the desired product, particularly intermolecular dimerization reactions. Incorporation of (3,5‐di‐tert‐butyl)phenyl endgroups (Ar*) provides increased stability, culminating in the stable and isolable [4]cumulene[4]Ar*. Cumulene[4]Ar*remains, however, susceptible to dimerization under pressing conditions, and[4]Ar*also readily reacts with electrophiles under mild conditions that lead to intramolecular cyclization. Given the structural complexity of the side products in these studies (compounds3,10,14,17,18), X‐ray crystallography plays a vital role in their identification.
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- Award ID(s):
- 2003411
- PAR ID:
- 10376730
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Journal of Physical Organic Chemistry
- Volume:
- 36
- Issue:
- 2
- ISSN:
- 0894-3230
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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