The Effect of Bulky Substituents on the Formation of Symmetrically Trisubstituted Triptycenes

Abstract

A series of 1,8-dichloroanthracene precursor molecules with substituents in C-10 position of different steric demand (cyclohexyl, tert-butyl, methyl, isopropyl, n-butyl, phenyl, benzyl, trimethylsilylethinyl) were synthesised and subjected to electrocyclic cycloadditions with chlorobenzyne generated from 3-chloroanthranilic acid. The aim was to steer the regioselectivity of the addition reaction by the steric repulsion between this C-10 substituent and the chlorine substituent at the benzyne intermediate. With H as C-10 substituent the reaction leads to 23 % syn and 77 % anti form. With the small methyl group a syn/anti ratio of 37:63 was achieved. Contrary to our expectations the large C-10 substituent tert-butyl

Syntheses and Structures of 10‐Trimethylelement‐Substituted 1,8‐Dichloroanthracenes

“…(14)] to 1.439(4) Å [C(2)-C(11)]} and from our previously published results for nbutyl-, cyclohexyl-, phenyl-or (trimethylsilyl)ethynyl-substituted 1,8-dichloroanthracenes. [3] The C(10)-Si(1) distance in 3 at 1.916(2) Å is remarkably long and very comparable to the C aryl -Si bond in 9,10-bis-(trimethylsilyl)anthracene [1.913(2) and 1.916(2) Å [6] ] and 9,10-bis(diisopropylsilyl)anthracene [1.906(4) [7a] and 1.904(2) Å, [7b] respectively]. In general, these C-Si bond elongations in 3 and the other mentioned alkylsilyl-substituted compounds seem to be caused by repulsive interactions of the aryl-bound hydrogen atoms with the silyl substituents.…”

“…In the case of Ant-GeMe 3 (4) the C(10)-Ge(1) bond of 1.986(3) Å is also longer than the C aryl -Ge distances found in 1,8-bis(trimethylgermyl)naphthalene (1.973 and 1.975 Å). [11] Related to the structure of Ant-CMe 3 (1; see Figure 2), [3] a steric repulsion of the hydrogen atoms in the 4-and 5- Figure 2. Molecular structure of Ant-CMe 3 (1) in the crystalline state, which is shown for comparison.…”

“…The 1 H NMR spectroscopic shifts of compounds 3, 4 and 5 are listed in Table 1; the shifts of the tert-butyl-substituted species 1 [3] are given for comparison.…”

“…P 2 O 5 , toluene, 80°C, 12 %. [3] and Ant-SnMe 3 (5) by salt elimination reactions. We discuss their crystal structures to determine the influence of the moiety in the 10-position and compare them with the results of quantum chemical calculations.…”

4'-Bromophenyl Triptycene-2,5-diol

“…In recent years, due to the number of practical applications in the field of liquid crystalline materials and liquid crystalline polymers [5,6], a great deal of interest has been shown in the study of the rigid "paddlewheel" structured triptycene [7], incorporation of these rigid pendant groups will substantially improve the mechanical properties of the polymers [8,9]. Polymers having bromine functional group can be ardently convert in to various functionalities in addition to hydroxyl moiety [10,11], there are adequately innumerable derivatives can be constructed.…”