224949-81-9Relevant academic research and scientific papers
New Lewis-acidic molybdenum(II) and tungsten(II) catalysts for intramolecular carbonyl erie and prins reactions. Reversal of the stereoselectivity of cyclization of citronellal
Kocovsky, Pavel,Ahmed, Ghafoor,Srogl, Jiri,Malkov, Andrei V.,Steele, John
, p. 2765 - 2775 (2007/10/03)
New Mo(II) complexes BnEt3N+[Mo(CO)4ClBr2]- (A) and Mo(CO)5(OTf)2 (B) and their W(II) congeners D and E have been developed as catalysts for the title reactions. Unlike other Lewis acids, the latter catalysts exhibit cis-stereoselectivity in the cyclization of citronellal (1 → 3 with A and 1 → 5 with B). Isotopic labeling allowed formulation of the reaction mechanism, according to which these complexes act as bulky Lewis acids, η1- coordinated to the carbonyl oxygen. The stereochemistry appears to be controlled by the protruding ligand L(p), which dictates the boatlike transition state III. The kinetically formed cis-alkenol 3 can be equilibrated by [Mo(CO)4Br2]2 (C) or ZnCl2 to its trans-epimer 2 via a retro-ene reaction.
