Synthesis and Diatropicity of trans-10b-Methyl-10c-undecyl- and trans-10b-Methyl-10c-pentadecyl-10b,10c-dihydropyrene. An Empirical Approach to a Semiquantitative Assessment of the Diamagnetic Ring Current in a [14]Annulene

Abstract

trans-10b- 3b and 3c, were obtained from the valence isomerization of their corresponding [2.2]cyclophanedienes 28a and 28b. The long internal alkyl chain in each case was previously introduced via a Wittig reaction followed by reduction. The cyclophanedienes were synthesized from their corresponding dithia-[3.3]cyclophanes via a Wittig rearrangement-Hofmann elimination sequence. Proton chemical shifts of H1′ to H9′ of the alkyl chains in 3b and 3c, respectively, are identical, suggesting that the C1′-C9′ section of the long alkyl chain in 3b or 3c has similar averaged conformational movement. Application of the Johnson-Bovey (J-B) model to 3b does not give a satisfactory correlation between the proton ring current shift and the out-of-plane distance. A direct empirical plot of the out-ofplane distance, D, against the proton ring current shifts, ∆δ, however, gives a curve similar to that obtained from the J-B model of benzene. This curve in fact corresponds to a linear relationship between D and log |∆δ|. Calculated ring current shifts of several derivatives of 10b,10c-dihydropyrene based on the above empirical correlation agree well with the reported experimental values. Our model shows that the experimental detectable limit for the diatropicity of 10b,10c-dihydropyrene is about 14 Å from the mean molecular plane. A similar empirical treatment based on the carbon chemical shifts of the n-undecyl chain in 3b gives unsatisfactory results. Our model does not support the prediction that the magnitude of ring current effect on proton and carbon chemical shifts is essentially the same at the sample position in space relative to the mean plane of delocalization of an aromatic π-electron cloud.

A DFT Study of the Thermal, Orbital Symmetry Forbidden, Cyclophanediene to Dihydropyrene Electrocyclic Reaction. Predictions to Improve the Dimethyldihydropyrene Photoswitches

“…To some extent, these predictions have already been verified by the reported experimental activation energies for the acyl derivatives 8 − 11 (vide supra). The syntheses of appropriately 15,16-disubstituted compounds, especially the dinitrile 17 , represent worthy goals, which are certainly not trivial since many substituents are readily lost from the 15,16-positions, leading to pyrene derivatives . We will report our efforts in this direction in the future.…”

The synthesis of trianglimines: on the scope and limitations of the [3 + 3] cyclocondensation reaction between (1R,2R)-diaminocyclohexane and aromatic dicarboxaldehydes

“…In the same way as for compound(23) 342 mg (1R,2R)diaminocyclohexane(22) (3 mmol) and 444 mg (3 mmol) 1,3diformyl-5-methylbenzene(21) gave trianglimine(25) (510 mg, 75%) as a white powder. Mp 212 ЊC; [α] 25 D ϩ220 (CHCl 3 , c = 0.1); ν max (Nujol)/cm Ϫ1 1642 (C᎐ ᎐ N); δ H (500 MHz; CDCl 3 ) 8.32 (6H, s, CH᎐ ᎐ N), 7.84 (3H, br s, Ar-H), 7.31 (6H, br s Ar-H), 3.43 (6H, m, N᎐ ᎐ CH), 2.36 (9H, s, Me), 1.52-2.03 (18H, m, CH 2 ); δ C (CDCl 3 ) 162.3, 136.9, 130.3, 126.3, 125.5, 74.5, 32.8, 25.0, 21.5; m/z (LSIMS) 679.4 (M ϩ ϩ H); CHN (Found: C, 79.5; H, 8.05; N, 11.9.…”

“…The majority of aromatic dicarboxaldehydes synthesised previously were obtained by double oxidation of benzylic alcohols, 19 double reduction of aromatic dinitriles or the Sommelet route using base hydrolysis of the corresponding tetrabromides. [20][21][22][23][24] In this work we report on the synthesis of aromatic dicarboxaldehydes using various directed dilithiation strategies followed by electrophilic quenching with DMF, which offer acceptable solutions to the synthetic problem. Isolated reports on dilithiation reactions have appeared in the literature and are referred to below.…”

Evidence for Homo-Conjugation between Two Revolving 14π-Electron Systems in 10b-Methyl-10c-[2-(10b,10c-dimethyl-10b,10c-dihydropyrenyl)]-10b,10c-dihydropyrene

“…There is appreciable downfield shift of H1,3, being in the deshielding zone of the internal dihydropyrenyl ring. On the other hand, the series of protons H1‘−H10‘ are strongly shielded, even for H7‘ being furthest from the molecular plane of the opposite dihydropyrene. The ring current of each dihydropyrene ring in 5 clearly extends to an appreciable distance with respective to each molecular plane.…”