An Experimental Estimation of Aromaticity Relative to That of Benzene. The Synthesis and NMR Properties of a Series of Highly Annelated Dimethyldihydropyrenes: Bridged Benzannulenes

Abstract

The synthesis of 13 trans-dimethyldihydropyrenes (bridged [ 14lannulenes) fused to one or more benzene, naphthalene, phenanthrene, phenalene, or quinoxaline rings and 6 cis-dihydropyrene derivatives from benzenoid precursors using either a thiacyclophane route or an electrocyclic addition of a furan to an annulyne followed by deoxygenation is reported. Their 'H NMR spectra are studied in detail to obtain correlations between 3 J~,~ coupling constants and the intemal methyl proton chemical shifts and also between the latter and the more distant external annulene ring proton shifts. These linear correlations are then used to obtain a relationship between the relative aromaticity of benzene and the fused ring in question, such that the aromaticity of the fused ring can be estimated relative to that of a benzene ring simply from a measurement of chemical shift in the fused annulene.

Bimetallic Coordination Insertion Polymerization of Unprotected Polar Monomers: Copolymerization of Amino Olefins and Ethylene by Dinickel Bisphenoxyiminato Catalysts

“…The bisphenoxyimines were synthesized as we described previously from the bisaldehydes from 5-a and 5-s. 1,3-dibromomesitylene was synthesized according to literature procedures. 6 3,5-dibromomesitol was synthesized by the dropwise addition of a solution of Br 2 (1.48 mL, 28.76 mmol, 2.61 equiv) in DCM (6 mL) through an addition funnel to a solution of mesitol (1.5 g, 11.01 mmol, 1 equiv) and iron powder (0.04 g, 0.71 mmol, 0.06 equiv) in DCM (11 ml) in a covered round bottom flask with a stirbar over 30 minutes. The resulting red solution was sitrred an additional 2.5 h before the reaction was quenched with aqueous sodium hydrosulfite (Na 2 S 2 O 4 ).…”

“…The anisotropic displacement factor exponent takes the form: -2p 2 [ h 2 a* 2 U 11 + ... + 2 h k a* b* U 12 ]. ____________________________________________________________________ U 11 U 22 U 33 U 23 U 13 U 12 ____________________________________________________________________ Ni(1A) 75 (8) 143 (7) 303(8) -11 (6) 37 (7) 78(6) Ni(2A) 120 (8) 157 (8) 305 (8) -24(6) 46 (7) 81(6) P(1A) 189 (13) 218 (12) 262 (13) 6 (9) 28 (9) 74 ( (9) 322 (9) 326(9) 0(7) 22(7) 92(7) Ni(2B) 226 (9) 312 (9) 352 (9) -33(7) 51(7) 95(7) P(1B) 306 (14) 334 (13) 331 (14) 12 (9) 28(9) 80(9) P(2B) 299 (14) 332 (13) …”

The Metacyclophanediene-Dihydropyrene Photochromic π Switch

“…By trapping the aryne 35 with other annelated furans, a variety of annelated dihydropyrenes could be made. [28] In photoswitches 23/24 and 27/28 were now accessible in gram quantities such that more complex systems could be ex-1995, we published [20] full details of the comparison of the older and newer methods. Interestingly and importantly, the plored.…”

“…Benzannelation in internal group Ϫ our attempts at introducing tert-butyl the [e] position has thus slowed the thermal return reaction, something that is desirable in a photochemical switch. [19] The naphtho[e] isomer 25 [20] [21] thermally returns to dhp 26 even more slowly. We have very recently made the tert-butyl-substituted compounds 27 and 28 such that comparison data with the parent can be made under the same conditions.…”

“…We intend to establish the kinetics of this reaction by analysis, to slow the thermal return reaction, the heats of formation of the two isomers should be approximately the low-temperature work in the future. Indeed, none of the [a] fused benzannulenes that we have made [20] [21] allow useful same. Irie et al [19] have come to the same conclusion, but have tackled the problem in a different manner.…”