Publication Date:
2014-01-24
Description:
Wolff–Kishner reduction reactions were investigated by DFT calculations for the first time. B3LYP/6-311+G(d,p) SCRF=(PCM, solvent = 1,2-ethanediol) optimizations were carried out. To investigate the role of the base catalyst, the base-free reaction was examined by the use of acetone, hydrazine (H 2 N–NH 2 ) and (H 2 O) 8 . A ready reaction channel of acetone → acetone hydrazine (Me 2 C=N–NH 2 ) was obtained. The channel involves two likely proton-transfer routes. However, it was found that the base-free reaction was unlikely at the N 2 extrusion step from the isopropyl diimine intermediate (Me 2 C(H)–N=N–H). Two base-catalyzed reactions were investigated by models of the ketone, H 2 N–NH 2 and OH − (H 2 O) 7 . Here, ketones are acetone and acetophenone. While routes of the ketone → hydrazone → diimine are similar, those from the diimines are different. From the isopropyl diimine, the N 2 extrusion and the C–H bond formation takes place concomitantly. The concomitance leads to the propane product concertedly. From the (1-phenyl)ethyl substituted diimine, a carbanion intermediate is formed. The para carbon of the phenyl ring of the anion is subject to the protonation, which leads to a 3-ethylidene-1,4-cyclohexadiene intermediate. Its [1,5]-hydrogen migration gives the ethylbenzene product. For both ketone substrates, the diimines undergoing E2 reactions were found to be key intermediates. Beilstein J. Org. Chem. 2014, 10, 259–270. doi:10.3762/bjoc.10.21
Keywords:
acetoneacetophenoneDFT calculationsdiimine intermediatereduction reactiontransition statesWolff–Kishner
Electronic ISSN:
1860-5397
Topics:
Chemistry and Pharmacology
Permalink