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The Reduction of Oxalic Amidines with Metallic Lithium: Preparation of Lithiated Bisamides [R″N(RR′N)C=C(NRR′)NR″]Li 2 and Their Use as Intermediates in a Novel Synthesis of Tetraaminoethenes
Author(s) -
Wenzel Matthias,
Lindauer Dirk,
Beckert Rainer,
Boese Roland,
Anders Ernst
Publication year - 1996
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19961290110
Subject(s) - chemistry , lithium (medication) , diethyl ether , molecule , medicinal chemistry , ether , metalation , electrophile , aryl , dihydrogen complex , ligand (biochemistry) , crystal structure , crystallography , metal , organic chemistry , hydride , alkyl , medicine , biochemistry , receptor , endocrinology , catalysis
Reduction of the 1,4‐diaza‐1,3‐butadiene substructure of hexasubstituted oxalic amidines with lithium metal yields the new lithium diamides 3 . Subsequent reaction of 3 with various electrophiles gives the title substances 4, 5 , and the acylated derivative 6 , respectively. The first SET step in this reaction is the formation of monolithium radical anions 2 , which were detected by EPR spectroscopy. The second electron transfer leads to the deeply colored dianions 3 . – In the case of compound 3a [ cis ‐ 3a · 3 Et 2 O], the X‐ray crystal structure reveals the cisoid arrangement of the bidental ligand and three molecules of diethyl ether which are located in a 2:1 fashion in the first coordination sphere of the lithium cations. The NMR 2D‐ 1 H, 6 Li‐HOESY investigations of 3a in [D 10 ]diethyl ether/diethyl ether (8:1) show Li + contacts to the hydrogen atoms of the ether molecules and to the ortho ‐hydrogen atoms of the aryl moieties. Results of semiempirical calculations (PM3) are throughout in acceptable agreement with the experimental data and explain the unusual coordination pattern of the lithium cations of compounds 3 .