M.C. White, Chem 153 Overview -287- Week of november 11. 2002 Unsolved problem: intermolecular sily formylation of terminal olefins Desired sily/formylation product. H H polyacetate polyol Observed silylformylation product SieTe CofCO)8(0.7 mol% C9 HSiEt2Me(l eq), co CoHo benzene.140C20h mj. product linear Route of the problem? One hypothesis is that hydrometalation of terminal olefins with Co-H occurs at a faster rate than silylmetalation with Co-SiR,. The overall result is the hydroformylated aldehyde product which can further react with Co-SiR3(recall Si is oxophilic) to give the silylenol ether. See Silylformylation, pg. 211 (OC)4C…Co(CO)4 HCo(CO)4\ R3SiCo(CO)4 Silylenol ether formation HCo(CO)4 regenerates the Co-H pecies DSik3 H Co(CO)4 R3Si-Co(CO)4 o(CO)4 Co(CO)3 CoIr CO)3M.C. White, Chem 153 Overview -287- Week of November 11, 2002 Unsolved problem: intermolecular silylformylation of terminal olefins Co2(CO)8 (0.7 mol%) HSiEt2Me (1 eq), CO benzene, 140oC, 20h C4H9 C4H9 OSiEt2Me mj. product linear Desired silylformylation product: R catalyst* CO, R3Si-H R O H SiR3 R O H OH * Tamao * oxidation acetate aldol equivalent polyacetate polyol Observed silylformylation product: (OC)4Co Co(CO)4 H SiR3 σ-bond metathesis HCo(CO)4 + R3SiCo(CO)4 HCo(I)(CO)4 R H Co(CO)4 R O Co(CO)3 R O Co(III)SiR3(CO)3 H R O H R3Si Co(CO)4 Co(CO)4 SiR3 R O H R OSiR3 Co(CO)4 H H R OSiEt2Me H + HSiR3 R Route of the problem? One hypothesis is that hydrometalation of terminal olefins with Co-H occurs at a faster rate than silylmetalation with Co-SiR3. The overall result is the hydroformylated aldehyde product which can further react with Co-SiR3 (recall Si is oxophilic) to give the silylenol ether. See Silylformylation, pg. 211. Silylenol ether formation regenerates the Co-H species