abnormal Reimer-Tiemann reaction
Theoretical, Physical and Computational Chemistry
Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
The molecular mechanism for the pyrrole ring expansion to yield 3-chloropyridine, as a model of the abnormal Reimer-Tiemann rearrangement, was characterized theoretically in vacuo by means of the HF/6-31G* computational method. The electron correlation was estimated at the MP2/6-31G* level and by calculations based on density functional theory, B3LYP/6- 31G* and B3LYP/6- 31+G*. Solvent effects of the diethyl ether and ethanol media were analyzed by using a polarizable continuum model. The stationary points were characterized with analytical gradient techniques in the gas phase and insolvents. The topology of the potential energy surfaces calculated at the MP2/6-31G* and B3LYP/6-31G* levels shows that the molecular mechanism corresponds to an inverted energy profile along one intermediate, associated with the addition of dichlorocarbene at the β-position of the pyrrole anion, and only one transition structure related to the ring expansion associated with the breaking and forming of Cα - Cβ and C - Cα bonds, respectively, and the Cl- leaving process. © 1998 John Wiley & Sons, Ltd.
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