34696-71-4

Upstream product

• 4333-56-6 cyclopropyl bromide 
• 22445-41-6 3,5-dimethylphenyl iodide 
• 556-96-7 5-bromo-1,3-xylene 
• 411235-57-9 cyclopropylboronic acid 

Relevant academic research and scientific papers

The copper-catalyzed ring-opening reactions of cyclopropanes by N-fluorobenzenesulfonimide toward N-allylsulfonamides

In this paper, we reported a copper-catalyzed ring-opening reaction of arylcyclopropanes by N-fluorobenzenesulfonimide, leading to N-allylsulfonamides in moderate to good yields. This procedure tolerated bromo, fluoro, trifluoromethyl, phenyl and alkyl groups in the phenyl, proceeding with a sequential ring-opening of arylcyclopropanes, and copper-mediated β-H elimination of alkyl radical.

Preferred conformation and barriers to internal rotation of ortho-disubstituted cyclopropylbenzenes

Schaefer's "J method" was employed to show that 2-cyclopropyl-1,3-dimethylbenzene (5) in solution prefers the perpendicular conformation in which the torsional angle Θ between the C(1)-H bond of the cyclopropyl group and the plane of the benzene ring is 90°. This is opposed to the situation in cyclopropylbenzene (3) where the bisected conformer (Θ = 0°) prevails. From the value of -0.85 ± 0.01 Hz for 6J(H-α,H-para) in 5 (for solutions in CS2 and in acetone) a barrier to rotation about the cyclopropyl-aryl bond of 6.4 kJ/mol can be derived if a predominantly two-fold potential and a vanishing 6J(H,H) for Θ = 0° are assumed. The introduction of the two orrho-methyl groups into 3 thus effectively interchanges the ground and transition state conformations of the internal rotation. This effect is well reproduced by ab initio (STO-3G and 6-31G*) and semiempirical (AMI) molecular orbital computations. The preference for the perpendicular conformation of an ortho-disubstituted cyclopropyl substituent was also demonstrated by a dynamic NMR study of 2-cyclopropyl-4-isopropyl-1,3,5-trimethylbenzene (10). Exchange-broadened 1H spectra due to slow rotation of the cyclopropyl group were only obtained near the low-temperature limit of the spectrometer (-140°C), and the barrier to rotation is estimated to lie near 28 kJ/mol (ΔG?). MM3 molecular mechanics computations suggest that the rather large increase of the rotational barrier in 10 relative to 5 is caused by the combined buttressing effect of the isopropyl and the 5-methyl groups. The present findings explain why an earlier attempt (in 1970) to determine the rotational barrier in 2-cyclopropyl-1,3,5-trimethylbenzene by dynamic NMR was bound to fail.