Iron-catalyzed transformations of 2-chloro-1,6-heptadienes

(Phosphane)iron complexes in the presence of excess trialkylaluminium reagents catalyze various transformations of 2-chloro-alpha,omega-dienes, depending on their structure. Most notably, in the cases of simple 2-chloro-1,6-heptadienes, cyclization with transfer of the alkyl group (Me and Et) from the corresponding trialkylaluminium compound was observed to give 2-alkyl-1-methylidenecyclopentanes. Reaction with 2-chloro-1,7-octadiene afforded the product of reductive dehalogenation. In the case of 2-chloro-4-aza-1,6-heptadiene a partial or complete hydrogenation of the double bonds was observed depending on the amount of trialkylaluminum reagent used. Interestingly, allyl(2-chloroallyl )malonate underwent C-C bond cleavage with the loss of an allyl group to give (2-chloroallyl)malonate. In the presence of ruthenium catalysts only reductive dehalogenation was observed. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004).