74687-07-3Relevant articles and documents
Efficient preparation of [1-15N]-3-cyano-4-methyl-1H-pyrrole by a Wittig-based strategy
Dawadi, Prativa B. S.,Lugtenburg, Johan
experimental part, p. 2288 - 2292 (2009/04/05)
3-Cyano-4-methyl-1H-pyrrole (1) was prepared by a new Wittig procedure from simple, commercially available starting materials in four steps with an overall yield of 39%. Similarly, [1-15N]-3-cyano-4-methyl-1H-pyrrole (1a) was prepared starting from [15N]-phthalimide. In this synthesis, Wittig coupling was used to form the central C-C bond of intermediate 6, which has nitrile and methyl substituents. Upon deprotection and cyclization pyrrole 1 is obtained directly in one pot. This scheme also allows stable isotope incorporation at any position or a combination of positions. 3-Cyano-4-methyl-1H-pyrrole was converted into the novel 1-benzyl-3-cyano-4- methylpyrrole and the novel 4-methyl-1H-pyrrole-3-aldehyde. It is clear that this novel Wittig procedure has a wide scope that will allow the easy preparation of many new pyrrole systems. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
The Timing of the Proton-Transfer Process in Carbonyl Additions and Related Reactions. General-Acid-Catalyzed Hydrolysis of Imines and N-Acylimines of Benzophenone
Sayer, J. M.,Conlon, Patrick
, p. 3592 - 3600 (2007/10/02)
Observed general-acid-catalyzed hydrolysis of benzophenone imines, Ph2C=NR, or the kinetically equivalent general-base-catalyzed hydrolysis of the conjugate acids Ph2C=N+HR, corresponds mechanistically to general-base-catalyzed amine expulsion from the conjugate acid (T+) of the tetrhedral intermediate from water addition to Ph2C=NR.Broensted β values for this catalysis by carboxylate and cacodylate ions are 0.96 (for R = H), 0.93 (for R = C2H4CN), and 0.76 (for R = CH2CN).These results, combined with calculations that suggest that amine expulsion from the zwitterionic intermediate, T+/-, from ammonia is slower than diffusion processes involving T+/- and catalyst, are consistent with a mechanism in which a simple proton transfer process is not rate determining.Because of the stability of T+/- it is likely that catalysis in this system is "enforced" by the lifetime of this intermediate.We suggest that catalysis of these reactions is observed because hydrogen bonding of T+/- to the conjugate acid of the catalyst provides an energetic advantage by stabilizing both T+/- and the transition state for amine expulsion from this species.Hydrolysis of N-acyl benzophenone imines, Ph2C=NC(O)CH2X (X = H, OCH3, or Cl), involves a rapid, favorable equilibrium for addition of water across the C=N bond, followed by amide expulsion from the carbinolamide.The latter process, analogous to amine expulsion from carbinolamines, is subject to weak general acid catalysis with Broensted α values of 0.5-0.6.This catalysis probably corresponds mechanistically either to (1) bifunctional or "one-encounter" catalysis in which one or both of the proton-transfer processes is "concerted" with C-N cleavage, or (2) general base catalysis of the expulsion of the O-protonated amide from Ph2C(OH)N+HC(OH)CH2X.For uncatalyzed carbinolamide cleavage a cyclic transition state with intramolecular proton transfer to the acyl oxygen is suggested to explain the observed insensitivity to substituents, X, of amide expulsion from the neutral carbinolamides, Ph2C(OH)NHC(O)CH2X.
