Valenzisomerisierungen am Tetramethylcyclobuten, IV

Huth, Andreas; Straub, Henner; Müller, Eugen

doi:10.1002/jlac.197319731111

Cited by 8 publications

(6 citation statements)

References 13 publications

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“…12OoC, dec.). ( 4 ) undergoes significant decomposition in solution at room temperature, even in the absence of air[61, but is surprisingly stable in crystalline form and transforms to the dimer (5)-without melting-only above 80°C.…”

Section: Isolation Of 3456-tetrarnethyl-lzdiphenylbenzocyclobutadmentioning

confidence: 99%

“…The hydrocarbon (4)17] has remarkable spectroscopic properties: the mass spectrum shows the molecular ion m/e 310 and the associated isotopic peak, but no significant fragmentation. The 'H-NMR spectrum (CH,Cl,) displays a multiplet at F=7.15-7.45 (10H) for the aromatic protons and only one singlet at 6= 1.93 (12H) for the four methyl groups.…”

Section: Isolation Of 3456-tetrarnethyl-lzdiphenylbenzocyclobutadmentioning

confidence: 99%

“…The extent to which the four methyl groups in ( 4 ) contribute to stabilization of the skeleton ( I b) is difficult to estimate.…”

Section: Isolation Of 3456-tetrarnethyl-lzdiphenylbenzocyclobutadmentioning

confidence: 99%

“…The mixture is then cooled to -20°C and the carmine red needles filtered off under suction (m. p. 120°C, dec.); yield 20%. 86,412 (1974) We present here our results on the synthesis and on some properties of the chiral macrobicyclic and macrotricyclic molecules ( 4 ) and ( 6 ) , which may function as ligands for metal cation^".^.^] as well as for molecules [']. The binaphthyl group has been selected as center of chirality in the recently described chiral macrocyclic polyethers[*.…”

Section: 456-tetramethyi-l2-diphenylbenzocyclobutadiene ( 4 )mentioning

confidence: 99%

“…94, 2537( 1972. [4] A. G. Anustussiou, E. Reichnianis, and R. L. Elliott, Tetrahedron Lett. 1973, 3805.…”

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confidence: 99%

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Isolation of 3,4,5,6‐Tetramethyl‐1,2‐diphenylbenzocyclobutadiene

Straub

1974

Angew. Chem. Int. Ed. Engl.

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study ( < -30"C)1111. This is best evidenced by the upfield shift of protons H' (by 23Hz) and H5 (by 32Hz) on going from ( 3 ) to ( 5 ) , which simply reflects the increased availability of the lone pair for limited delocalization but is clearly inconsistent with the development of the diamagnetic ring current expected of this system. Obviously, the present findings indicate that neither 3-benzazonine ( 3 ) , at ambient temperature, nor the corresponding base ( 5 ) , generated at ca. -70 "C and observed at -35 'C[''], are capable of sustaining a ring current, ie., they are no more than benzopolyenes under the experimental conditions employed here.Interestingly the behavior of (3) and ( 5 ) sharply contrasts with that of their iso-x-electronic carbocycle, the benzocyclononatetraenyl anion (6) which was recently shown['21 to possess a well delocalized 14x frame exhibiting strong ring diamagnetism over a wide temperature range (-55 to + 35 "C).

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Section: Isolation Of 3456-tetrarnethyl-lzdiphenylbenzocyclobutadmentioning

confidence: 99%

Section: Isolation Of 3456-tetrarnethyl-lzdiphenylbenzocyclobutadmentioning

confidence: 99%

“…The extent to which the four methyl groups in ( 4 ) contribute to stabilization of the skeleton ( I b) is difficult to estimate.…”

Section: Isolation Of 3456-tetrarnethyl-lzdiphenylbenzocyclobutadmentioning

confidence: 99%

Section: 456-tetramethyi-l2-diphenylbenzocyclobutadiene ( 4 )mentioning

confidence: 99%

“…94, 2537( 1972. [4] A. G. Anustussiou, E. Reichnianis, and R. L. Elliott, Tetrahedron Lett. 1973, 3805.…”

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