Empirisches Inkrementsystem für Methylgruppensignale sowie Ringstrombeeinflussung der Protonen‐NMR‐Spektren methylsubstituierter Biphenylderivate

Abstract

Von 18 methylsubstituierten Biphenylderivaten werden 36 Methylgruppen-NMR-Signale durch multiple lineare Regressionsanalyse auf 4.4'-und 2,2'-Positions-Substituentenkonstanten analysiert. Der EinfluR des Verdrillungswinkels Q auf die o-Methylgruppensignale steigt von -0.095, -0.284, -0.345 auf -0.377 pprn fur Q = 5 8 " , 77.5'. 85" und 90". Diese Werte werden am besten durch das theoretische Ringstrommodell von Johnson und Bouey wiedergegeben. 36 methyl group NMR signals of 18 methyl-substituted biphenyl derivatives have been analyzed by multiple linear regression analysis to derive 4,4'-and 2,2'-position substitution constants. The influence of the torsional angle Q on the signals of o-methyl groups increases from -0.095, -0.284, -0.345 to -0.377 pprn for @ = 5 8 " , 77.5", 8 5 " , and 90". These values are in good agreement with the theoretical ringcurrent model of Johnson and Bouey. Insgesamt sind 209 verschiedene methylsubstituierte Biphenylderivate formulierbar '), von denen wir die bis auf 6,12 und 13 bekannten Verbindungen 1 -18 dargestellt haben, um ihre Protonen-NMR-Spektren bei 90 MHz unter vergleichbaren Bedingungen mittels Fourier-Transform-NMR-Spektroskopie (FT) zu untersuchen. FT-NMR-Daten unterscheiden sich numerisch stark von den friiher iiblichen CW-Spektrometerdaten", und zeigen den groaen Vorteil, daB unabhangige Messungen an verschiedenen Substanzen in verdiinnten CDC13-Ldsungen (2proz.) innerhalb der spektroskopischen Auflosung von 0.003 ppm reproduzierbare und somit zuverlassig vergleichbare chemische Verschiebungswerte liefern". Damit entfallt z. B. die Notwendigkeit, zur Ermittlung von Ringstromanisotropieeffekten bei benzoiden Aromaten die Aufspaltung zwischen den o,o'und p-Methylgruppensignalen eines Mesitylsubstituenten zu betrach-ten3-", wobei das p-Methylgruppensignal als internes Standardsignal gewlhlt wurde, das als unbeeinflunt vom Ringstromanisotropieeffekt des sondierten Aromaten angenommen wurde.

Highly Active Palladium Catalysts for Suzuki Coupling Reactions

“…2,5-Dimethylbiphenyl. ( Reaction was run at room temperature, ligand 2 was used). The coupling of 2-bromo- p -xylene with phenylboronic acid was effected using the general procedure with ligand 2 to afford 175 mg (96%) of the title compound as a colorless oil.…”

“…The coupling of 4-chloroacetophenone with phenylboronic acid was effected using the general procedure with toluene solvent, a reaction temperature of 100 °C, and 100 μL of a catalyst solution composed of Pd(OAc) 2 (2.2 mg, 0.01 mmol), ligand 4 (6.0 mg, 0.02 mmol), and THF (5 mL) to afford 178 mg (91%) of the title compound as a white solid, mp 120−121 °C (lit. mp 109−110 °C) …”

“…4-Acetylbiphenyl. (0.000001 mol % Pd, K 3 PO 4 as base, from the aryl bromide). The coupling of 4-bromoacetophenone with phenylboronic acid was effected using the general procedure with toluene solvent, a reaction temperature of 100 °C, and 10 μL of a catalyst solution prepared as follows: in 20 mL of THF in a flask in an argon-filled glovebox were dissolved Pd(OAc) 2 (4.5 mg, 0.02 mmol) and ligand 4 (12.0 mg, 0.04 mmol).…”

1H‐NMR study of some new acetyl dimethylbiphenyls: unambiguous signal assignment for the methyl groups

“…It is assumed [13], that the dihedral angle between ring A and B in biphenyl systems is 26 ± 5 • . In compound 1a this angle becomes [16] 70.5 • or close to perpendicular [4]. This explains the values of 2.12 and 2.11 ppm obtained for the 2-methyl (ring A) in 2a and 3a respectively, and it is anticipated that the dihedral angle in 3a is nearly perpendicular.…”

A New Mixed P,S‐Bidentate Ligand Featuring a λ4‐Phosphinine Anion and a Phosphanyl Sulfide Group − Synthesis, X‐ray Crystal Structures and Catalytic Properties of Its Chloro(cymene)ruthenium and Allylpalladium Complexes

“…[60] X-ray Crystallographic Study: Crystals of 3 and 7a suitable for Xray diffraction were obtained by slow diffusion of hexane into a CH 2 Cl 2 solution of 3 and 7a. Crystals of 5a suitable for X-ray diffraction deposited overnight from a solution in C 6 D 6 .…”