Construction of Nitrogen‐Heterocyclic Compounds Through Zirconium‐Mediated Intramolecular Alkene‐Carbonyl Coupling Reaction of N‐(o‐Alkenylaryl)carbamate Derivatives.

Abstract

Reactions of organo-metal compounds Reactions of organo-metal compounds O 0350Construction of Nitrogen-Heterocyclic Compounds Through Zirconium-Mediated Intramolecular Alkene-Carbonyl Coupling Reaction of N-(o-Alkenylaryl)carbamate Derivatives. -The outcome of the reaction between N-(o-alkenylaryl)carbamates and zirconocene complexes strongly depends on the nature of the N-substituent. Thus, N-benzyl derivatives undergo convenient ring closure to afford fused lactams. In contrast, starting from N-tosyl derivatives, only desulfonylation and/or ester transfer products are obtained. Aliphatic N-benzyl carbamates predominantly undergo decomposition. -(TAKIGAWA, Y.; ITO, H.; OMODERA, K.; ITO, M.; TAGUCHI*, T.; Tetrahedron 60 (2004) 6, 1385-1392; Sch. Pharm., Univ. Pharm. Life Sci., Hachioji, Tokyo 192, Japan; Eng.) -Jannicke 22-080 2004 Reactions of organo-metal compounds

Isomerization of Allylbenzenes

“…Of additional interest is that the majority of examples involving group 4 organometallic complexes require activation by the aluminum complex, methylalumoxane (MAO). In terms of other zirconocene complexes, Negishi and co-workers demonstrated that n Bu 2 ZrCp 2 was an effective isomerization catalyst of (2-deuterioallyl)­benzene, while Taguchi and researchers encountered isomerization of tert -butyl 2-allylphenyl­[(4-methylphenyl)­sulfonyl]­carbonate with the zirconium–butene complex prepared from Cp 2 ZrCl 2 and n butyllithium …”

“…In terms of other zirconocene complexes, Negishi and co-workers demonstrated that n Bu 2 ZrCp 2 was an effective isomerization catalyst of (2-deuterioallyl)benzene, 804 while Taguchi and researchers encountered isomerization of tert-butyl 2allylphenyl[(4-methylphenyl)sulfonyl]carbonate with the zirconium−butene complex prepared from Cp 2 ZrCl 2 and n butyllithium. 805 Rao and Periasamy discovered that a mixture of Cp 2 TiCl 2 (20 mol %), Grignard-grade magnesium, and BrCH 2 CH 2 Br facilitated the double bond rearrangement of allylbenzene 3 and safrole 6 into the respective trans products 4 and 19 in yields of 77% and 80% (Scheme 164). 806 Of importance here is that these conditions have the added advantage of being effective at room temperature and that isomerizations were complete within 2 h. In a subsequent publication, the authors postulated that under the reaction conditions a titanocene−ethylene complex and/or a titanium hydride species could be the agents responsible for the observed isomerization process.…”