202191-34-2Relevant academic research and scientific papers
Coupling of η3-allyl and alkyne in molybdenum carbonyl complexes
Barrado, Georgina,Hricko, Margaret M.,Miguel, Daniel,Riera, Víctor,Wally, Hans,García-Granda, Santiago
, p. 820 - 826 (1998)
The complexes [Mo(η3allyl)(CO)2(S2PX2)(NCMe)] (X = OEt (la), Ph (1b)) react with DMAD (dimethyl acetylenedicarboxylate) to give the tricarbonyl complexes [Mo(CO)3(S2PX2){OC-(OMe)C(allyl)=CCO 2Me}] (2a,b) in a reaction involving the coupling of allyl and alkyne. Subsequent addition of PEt3 affords crystalline, air-stable dicarbonyl complexes [Mo(CO)2-(PEt3)(S2PX 2){OC(OMe)C(allyl)=CCO2Me}] (3a,b). An X-ray structural analysis of the dithiophosphinate derivative 3b reveals that the alkenyl ligand is stabilized through intramolecular coordination of one oxygen of the ester group to the metal, forming a five-membered oxametallacycle. The alkenyl ligand shows unusual trans stereochemistry in contrast to the cis disposition usually found in previous examples of metal-mediated η3-allyl - alkyne coupling. Demetalation of the organic moiety can be easily afforded by reaction with air or HCl gas to give the corresponding 2-allyl fumarate 4 in high yield. Regioselectivity studies employing 1-methylallyl complexes reveal that the reaction is strongly influenced by the dithio ligand bonded to molybdenum. In all cases reaction at the more substituted carbon of the allyl is favored.
