Molybdenum(II)- and Tungsten(II)-Catalyzed Allylic Substitution.
The molybdenum(II) complexes Mo(CO)(5)(OTf)(2) (7a), [Mo(CO)(4)Br(2)](2) (8a), their tungsten(II) congeners 7b and 8b, and bimetallic complex Mo(CO)(3)(MeCN)(2)(SnCl(3))Cl (9a) have been found to catalyze the C-C bond-forming allylic substitution with silyl enol ethers derived from beta-dicarbonyls (e.g., 16 + 30 --> 46) or from simple ketones (e.g., 16 + 32 --> 50), aldehydes, and esters as nucleophiles under mild conditions (room temperature, 1-2 h). Methanol, as a prototype oxygen nucleophile, reacts in a similar fashion (e.g., 16 + MeOH --> 43). Mechanistic and stereochemical experiments are indicative of Lewis-acid catalysis rather than a metal template-controlled process.
Malkov
Andrei V.
AV
Department of Chemistry, University of Leicester, Leicester LE1 7RH, U.K., and AgrEvo UK Ltd., Chesterford Park, Saffron Walden, Essex, CB10 1XL, U.K.
Baxendale
Ian R.
IR
Dvorák
Dalimil
D
Mansfield
Darren J.
DJ
Kocovský
Pavel
P