The barrier to rotation in 2,2″-dimethyl-o-terphenyl and several 3,3″-derivatives (rotational isomers of 1,2-di-o-tolylbenzene)

Abstract

The synthesis and measurement of the barrier to rotation [Formula: see text] in 2,2″-dimethyl-o-terphenyl (62 kJ/mol) and the following 3,3″-disubstituted derivatives is described (Cl, Cl, 74 kJ/mol), (Cl, CN, 70 kJ/mol), (CM, CN 70 kJ/mol), (CHO, 75 kJ/mol). For 3,3″-bis-CH2Br, Δv, the separation of the —CH3 peaks in the 1Hmr spectrum, was too small to obtain [Formula: see text]

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

“…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.…”

“…In the same way as for compound (15) 1 g 1,3-dibromo-5-methylbenzene (4 mmol) gave the title compound as a white solid. In the same way as for compound (23) A solution of 30 mg (0.133 mmol) of 1,3,5-trimethoxy-2,4-diformylbenzene (11) in dichloromethane (1.5 ml) was added to a solution of (1R,2R)-diaminocyclohexane (22) (15 mg) in 1.33 ml of dichloromethane at rt and stirred for 3 hours under reflux. The solvent was evaporated and the title compound was obtained after recrystallisation from ethyl acetate as a white powder.…”

Stereomutations of Conformational Atropisomers of Hindered 1,2-Diaryltetrahydropyrimidines

“…Such a situation entails the existence of two enantiomers (atropisomers) when the rotation rate about the heterocyclic and o ‐iodophenyl moieties is negligible. The MM‐computed ground‐state structures for the atropisomers of 1 are shown in Scheme a, and identified as enantiomers ( M ) and ( P ) 4…”

Solvent and structure effects on rotamerization in 3,4‐alkylenedioxy‐ and 3,4‐dialkoxy‐2,5‐bis[di(tert‐butyl) hydroxymethyl]thiophenes: an NMR, IR, molecular mechanics and single‐crystal x‐ray study

“…Although the discussion of restricted rotation is often limited to that about a single axis, there has been much work on systems with more than one rotor. Apart from situations where two, three or four rotors are attached to one atom (carbon or heteroatom), which are numerous but outside the scope of this work, many systems have been described where two or more rotors are attached to a common aromatic nucleus, such as benzene, [1][2][3][4][5][6][7] naphthalene, [8][9][10][11][12][13][14][15][16][17] anthracene, 18 etc. 19 or, less frequently, to a heterocyclic group.…”

“…19 or, less frequently, to a heterocyclic group. 20,21 In almost all studies the two or more rotors, often neopentyl, 1,2,9c,21a substituted phenyl 3,4,6,[7][8][9][10][11][12][13][14][15][18][19][20] or 1-naphthyl, 7de,13e are identical and indistinguishable (for an exception, see Ref. 22; see also Ref.…”