116074-33-0Relevant academic research and scientific papers
Resonance Effects in the Solvolysis of α -t-Butyl- α-neopentylbenzyl and α-t-Butyl-α-isopropylbenzyl p-Nitrobenzoates
Fujio, Mizue,Ohe, Makoto,Nakata, Kazuhide,Tsuji, Yutaka,Mishima, Masaaki,Tsuno, Yuho
, p. 929 - 936 (2007/10/03)
Substituent effects on the solvolysis rates of α-t-butyl-α-neopentylbenz.yl and α-t-butyl-α-isopropylbenzyl p-nitroben/oates in 50% (v/v) aqueous EtOH at 75 °C were correlated with the Yukawa-Tsuno equation to give p = -3.37 and r = 0.78. and p= -3.09 and r = 0.68, respectively. The reduction in r values from r= 1.00 characteristic of full conjugation is ascribed to deviation from coplanarity of the carbocationic center and the benzylic π-system in the transition state. The torsion angles for twisting out of coplanarity were estimated from the relationship r/rmax = cos2 θ for a series of sterically hindered tertiary dialkylbenzylic solvolyses. The torsion angles assigned for these twisted benzylic systems are in good agreement with theoretically calculated dihedral angles of the corresponding 6-3IG * optimized carbenium ions. This identity provides convincing evidence for occurrence of steric inhibition of resonance through loss of coplanarity, and, in turn, provides strong support for our characterization of the r value as a resonance demand parameter reflecting the degree of resonance (π-delocalization) interaction between an aryl group and the reaction site.
Steric and Stereoelectronic Effects in the Hydrogenolysis and Birch Reduction of Some Hindered Tertiary-Benzylic Carbinols
Collins, David J.,Jacobs, Howard A.
, p. 1989 - 2004 (2007/10/02)
3-(4'-Methoxyphenyl)pentan-3-ol (3a) and 3-(4'-methoxyphenyl)-2,4-dimethylpentan-3-ol (3b) underwent catalytic hydrogenolysis over 10percent palladium/charcoal at moderate temperatures and pressures.The more hindered tertiary-benzylic carbinols 3-(4'-methoxyphenyl)-2,2,4-trimethylpentan-3-ol (6), 3-(4'-methoxyphenyl)-2,2,4,4-tetramethylpentan-3-ol (3c), 1-(4'-methoxyphenyl)-2,2,6,6-tetramethylcyclohexan-1-ol (8) and 1-(1',1'-dimethylethyl)-6-methoxy-2,2-dimethyl-1,2,3,4-tetrahydronaphthalen-1-ol (10) were completely resistant to hydrogenolysis, even under vigorous conditions.While the hindered tertiary-benzylic carbinols (6), (8) and (10) readily underwent Birch reduction, the analogous di-t-butyl anisyl carbinol (3c) was unchanged.The failure of (3c) to undergo Birch reduction is probably due to a hitherto unrecognized stereoelectronic effect: the C-OH bond of (3c) is constrained to lie more or less in the plane of the benzene ring, and addition of an electron to the benzene ring of the derived oxyanion (31) is inhibited in this conformation.
