Synthesis of stable primary enamines from (butadiene)zirconocene and benzylic nitriles

• Published in: Tetrahedron letters Vol. 35; no. 36; pp. 6665 - 6668
• Main Authors: Erker, Gerhard, Kowalski, Dorothee, Noe, Ralf, Krüger, Carl, Nolte, Matthias
• Format: Journal Article
• Language: English
• Published: OXFORD Elsevier Ltd 05.09.1994; Elsevier
• Subjects: Chemistry; Chemistry, Organic; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Organic chemistry; Organic compounds; Organometalloidal and organometallic compounds; Physical Sciences; Physics; Science & Technology; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; KETONE; CONVERSION; DIENE COMPLEXES; CONJUGATED PRIMARY ENAMINES; CARBENE COMPLEXES; METALLACYCLIC ZIRCONOXYCARBENE COMPLEXES; HEXACARBONYLTUNGSTEN; Nitrile; Trienic compound; Molecular structure; Nitrogen heterocycle; Enamine; Organic ligand; Metallocycle; Zirconium Complexes; Zirconium Organic compounds; Experimental study; X ray diffraction; Metallocene; Hydrolysis; Diamine; Cyclization; Addition reaction; Benzenic compound; Organic compounds; Crystalline structure
• ISSN: 0040-4039; 1873-3581
• DOI: 10.1016/S0040-4039(00)73462-9

(Butadiene)zirconocene adds two molar equivalents of benzyl cyanide to give the chiral nine-membered metallacycle 4. Controlled hydrolysis (CH 3OH) of 4 yields the stable conjugated primary enamine 2,7-diamino-1,8-diphenyl-2,4,6-octatriene ( 6) (≥70% isolated). (2-Pyridyl)acetonitrile reacts similarly with the (butadiene)zirconocene reagent. Subsequent controlled hydrolysis now produces a non-conjugated primary enamine, namely 2,7-diamino-1,8-di(2-pyridyl)-1,4,7-octatriene ( 9). In this case, conjugative stabilization of a primary enamine is overcome by functional group stabilization by the 2-pyridyl substituent at the β-enamine position. The template coupling of (butadiene)zirconocene with benzyl cynaide followed by controlled hydrolysis yields the stable conjugated primary enamine 6.