338460-23-4Relevant academic research and scientific papers
Spectroscopic and kinetic evidence for an accumulating intermediate in an SNV reaction with amine nucleophiles. Reaction of methyl β-methylthio-α-nitrocinnamate with piperidine and morpholine
Bernasconi, Claude F.,Brown, Shoshana D.,Eventova, Irina,Rappoport, Zvi
, p. 3302 - 3310 (2007)
(Chemical Equation Presented) A spectroscopic and kinetic study of the reaction of methyl β-methylthio-α-nitrocinnamate (4-SMe) with morpholine, piperidine, and hydroxide ion in 50% DMSO/50% water (v/v) at 20 °C is reported. The reactions of 4-SMe with pi
Amine catalysis in the vinylic substitution of α-methylthio-α-arylmethylene Meldrum's acids and its absence in the substitution of methyl β-iodo-α-nitrocinnamate by amines
Beit-Yannai,Chen,Rappoport
, p. 1534 - 1545 (2007/10/03)
Substitution of the iodine of (E)- and (Z)-methyl β-iodo-α-nitrocinnamates (5) by amines gives identical (Z)-enamines with aniline (Ani) and piperidine (Pip). No amine catalysis was observed with Pip, Ani, morpholine (Mor), orp-MeOC6H4NHMe (MMA) in MeCN nor with Pip or Mor in EtOH: kPip/kMor = 115-138 (MeCN), 3.3-6.9 (EtOH); kMeCN/kEtOH = 25.5 ± 2.2 (Pip), 0.79-1.16 (Mor); k(Z)-5/k(E)-5 = 1.3-2.9 (13.5 with MMA in MeCN). Replacement of the MeS group in six α-amethylthio-α-arylmethylene Meldrum's acid (6-X) by Pip resulted in amine catalysis in MeCN and EtOH. In EtOH, the p-anisyl derivative (6-MeO) and in MeCN 6-MeO, 6-Me and 6-H displayed second order catalysis in Pip. Other 6-X compounds show orders between one and two in Pip with amine catalyzed (k3B)/non-catalyzed (k2) rate coefficient ratios of 281-731 (EtOH) and 504-635 (MeCN) at 30°C. kMeCN/kEtOH = 3.0-4.9. In MeCN ΔH? = -0.8 to -5.9 kcal mol-1 and ΔS? = -50 to -72 e.u. An intermediate zwitterion, 3a, is formed in all cases. For system 5 the rate of I- expulsion from 3a exceeds its deprotonation rate, and the observed rate coefficient is composite: kobs = k1k2/k-1 in MeCN (k1 = rate coefficient of nucleophilic attack) but kobs = k1 in EtOH. In MeCN the deprotonation is faster than the expulsion rate of MeS-, and more so for 6-X with X = p-Br, p-CF3, m,m′-(CF3)2. Different electrophilicities of 6-X, different extents of hydrogen bonding, steric and electronic effects account for the kinetic differences.
