Anwendungsbreite der reduktiven Kupplung aromatischer Aldimin‐Derivate mit niedervalenten Titan‐Reagenzien zu 1,2‐Diarylethylendiaminen
1988; Wiley; Volume: 71; Issue: 8 Linguagem: Inglês
10.1002/hlca.19880710818
ISSN1522-2675
AutoresClaudia Betschart, Beat Schmidt, Dieter Seebàch,
Tópico(s)Synthetic Organic Chemistry Methods
ResumoScope and Limitations of the Reductive Coupling of Aromatic Aldimine Derivatives with Formation of 1,2‐Diarylethylenediamine Units, Using Low‐Valent Titanium Reagents Besides the adducts from lithium amides to aromatic aldehydes, iminium salts, animals, and N ‐silylimines of aromatic aldehydes are coupled by the black suspension obtained from TiCL 4 and Mg turnings in tetrahydrofuran (THF). The 1,2‐diarylethylenediamines with tertiary and primary amino groups thus obtained are formed with no or only moderate diastereoselectivity (products 4a–d (Scheme 2) and 5–e (Scheme 3) , respectively); the amine component may contain a strained ring or additional heteroatoms as in azetidin, bis(2‐methoxyethyl)amine, piperazine, morpholine, and thiomorpholine (products 6a–e ; Table 1 ). By an in ‐ situ procedure, ethylenediamines exclusively trans ‐diaryl‐substituted piperazine and perhydro‐1,4‐diazepine derivatives (products 7a–f ; Table 2 ). Enantiomerically pure monocyclic trans,cis ‐5‐alkyl‐2,‐3‐diaryl‐piperazines and diazabicyclo[4.3.0]nonanes and ‐[4.4.0]decanes are obtained by employing suitable diamines prepared from the amino acids (S) ‐alanine, (S) ‐phenylalanine, (S) ‐proline and from ( S,S )‐ or ( R,R )‐cyclohexane‐1,2‐diamine, respectively (products 11a–i , 7e ; Table 4 ). The configuration of all products are derived from the high‐field NMR spectra, some of which are discussed in detail ( Figs. 1 and 2, Tables 3 and 5 ); all new compounds are fully characterized by their physical data. Depending upon the structure of the components employed, the yields of purified products range from as low as 7% to essentially quantitative.
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